Patent Application
20100081941
The present invention relates generally to the field of assessing a patient's cardiovascular health. More particularly, the invention relates to providing a comprehensive cardiovascular assessment of a patient by associating functional, risk factor, and structural assessments of the patient's cardiovascular system.
Cardiovascular disease (CVD) is the leading cause of death in the United States and most developed countries. The epidemic of CVD is growing fast in the developing countries as well as the under privileged part of developed societies who cannot afford advanced and often expensive diagnostic and therapeutic modalities. It is now well documented that almost all cases of CVD are due to atherosclerotic cardiovascular disease and manifest predominantly by heart attack and stroke. The unpredictable nature of heart attack and the need for cost-effective screening in large groups of asymptomatic at-risk populations are unsolved problems in cardiovascular healthcare.
In the past 50 years, although numerous risk factors for atherosclerosis have been identified, the ability to predict a cardiovascular event, particularly in the near term, remains elusive. Numerous population studies have shown that over 90% of CVD patients have one or more risk factors (high cholesterol, blood pressure, smoking, diabetes etc.). However, 70-80% of the non-CVD population also has one or more risk factors. Over 200 risk factors have been reported, including a number of emerging serologic markers. For example, lipid profiles (Total cholesterol, LDL, HDL, triglycerides), homocysteine, and C-reactive protein (CRP) have been adapted for coronary risk assessment.
High blood cholesterol is a major risk factor for coronary heart disease and stroke. Cholesterol plays a major role in a person's heart health. The National Cholesterol Education Program (NCEP) has guidelines for detection and treatment of high cholesterol. The Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III or ATP III) was released in 2001. The report recommends that everyone age 20 and older have a fasting “lipoprotein profile” every five years. This blood test is performed after a 9-12-hour fast without food, liquids or pills and gives information about total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides. Based on combining this lipoprotein information with a Framingham Risk Score (FRS), the NCEP has developed thresholds to guide initiation of therapeutic lifestyle changes and/or drug therapy.
The FRS is a coronary prediction algorithm that seeks to provide an estimate of total coronary heart disease (CHD) risk (risk of developing one of the following: angina pectoris, myocardial infarction, or coronary disease death) over the next 10 years. Separate score sheets are used for men and women, and the factors used to estimate risk include age, total blood cholesterol, HDL cholesterol, blood pressure, cigarette smoking, and diabetes mellitus. Relative risk for CHD is estimated by comparison to low-risk Framingham participants of the same age, optimal blood pressure, total cholesterol 160-199 mg/dL, HDL cholesterol 45 mg/dL for men or 55 mg/dL for women, non-smoker and no diabetes. The Framingham Heart Study risk algorithm encompasses only coronary heart disease (CHD), not other heart and vascular diseases, and was based on a study population that was almost all Caucasian. Wilson P W F, et al. “Prediction of coronary heart disease using risk factor categories” Circulation 97 (1998) 1837-1847. In addition, the Framingham Risk Score is heavily weighted by age and sex and thus has low predictive value for individuals under 55 and for women.
A sensitive screening test for early atherosclerotic vascular disease should correlate with the magnitude of Framingham Risk Estimates, and should predict CHD vs. absence of CHD. However, Framingham risk estimates are intended to predict risk of future CHD events, not presence of CHD. A >20% 10-year estimated risk is regarded as “CHD-equivalent.” It is noteworthy that new guidelines consider diabetes as a “CHD equivalent.” An incremental predictive value over FRS for CHD suggests a complementary or alternative clinical utility and provides an impetus for the present invention.
Further, a recent guideline has brought to light the need for direct and individualized assessment of cardiovascular health, beyond the mere assessment of risk factors. (Naghavi et al. From Vulnerable Plaque to Vulnerable Patient. Executive Summary of the Screening for Heart Attack Prevention and Education (SHAPE) Task Force Report. The American J. of Cardiology. Supplement to vol 98, no. 2. Jul. 17, 2006). As highlighted in the SHAPE Guideline, current primary prevention recommendations from initial assessments and risk stratification are based on traditional risk factors (e.g., the Framingham Risk Score in the United States and the SCORE in Europe), followed by goal-directed therapy when necessary. Although this approach may identify persons at very low or very high risk of a heart attack or stroke within the next 10 years, the majority of the population belongs to an intermediate-risk group, in which the predictive power of risk factors is low. Indeed, most heart attacks occur in this intermediate-risk group.
Consequently, many individuals at-risk will not be properly identified and will not be treated to attain appropriate “individualized” goals. Others will be erroneously classified as high risk and may be unnecessarily treated with drug therapy for the rest of their lives. (See also Akosah K, et al., “Preventing myocardial infarction in the young adult in the first place: how do the National Cholesterol Education Panel III guidelines perform?,” J Am Coll Cardiol. 2003 May 7; 41(9):1475-9; Brindle P, et al. “Predictive accuracy of the Framingham coronary risk score in British men: prospective cohort study,” BMJ, 2003 Nov. 29, 327 (7426):1267; Empana J P, et al., “Are the Framingham and PROCAM coronary heart disease risk functions applicable to different European populations? The PRIME Study,” Eur Heart J. 2003 November 24(21):1903-11; Neuhauser H K, et al. “A comparison of Framingham and SCORE-based cardiovascular risk estimates in participants of the German National Health Interview and Examination Survey 1998,” Eur J Cardiovasc Prey Rehabil, 2005 October 12(5):442-50; Bastuji-Garin S, et al., “Intervention as a Goal in Hypertension Treatment Study Group. The Framingham prediction rule is not valid in a European population of treated hypertensive patients,” J. Hypertens. 2002 October 20(10):1973-80.) In short, the predictive accuracy of risk factor analysis, when performed alone in a given individual, is poor. The SHAPE Guideline highlights the need for structural and functional assessment of the arterial system, in addition to risk factor analysis, and also recognizes insufficiencies in available tools for structural and functional assessments of atherosclerosis.
Assessment of cardiovascular function has focused on the endothelial system. Endothelial function (EF) is accepted as a sensitive indicator of vascular function. EF has been labeled a “barometer of cardiovascular risk” and is well-recognized as the target of cardiovascular disease. Endothelial cells comprise the innermost lining of the vasculature. In addition to forming a physical barrier, endothelial cells play a central role in multiple regulatory systems including vasomotion, inflammation, thrombosis, tissue growth and angiogenesis. When there is increased demand for blood by organs of the body, endothelial cells release nitric oxide (NO), which increases the diameter of arteries and thereby increases blood flow. Nitric oxide is important not only for the regulation of vascular tone but also for its roles in the modulation of cardiac contractility, response to vessel injury, and development of atherosclerosis. Presence of atherosclerosis hampers the normal functioning of these cells, blocking NO-mediated vasodilation and making the arteries stiffer and less able to expand and contract. The loss of ability of an artery to respond to increased and sudden demand is called endothelial dysfunction (EDF).
Endothelial dysfunction is associated with virtually all of the cardiovascular risk factors, and endothelial failure is the end stage that leads to clinical events in cardiovascular disease. Numerous experimental, clinical, and epidemiologic studies have shown that endothelial function is altered in the presence of established risk factors such as hypertension, hypercholesterolemia, diabetes mellitus and emerging risk factors such as hyperhomocysteinemia, CRP, and fibrinogen. Evidence showing strong correlations between endothelial dysfunction and other sub-clinical markers of atherosclerosis, such as carotid intima media thickness (IMT), coronary calcium score (CCS), and ankle brachial index (ABI), has also emerged. More importantly, endothelial dysfunction has been reported to be predictive of coronary, cerebro-vascular and peripheral arterial disease and {HYPERLINK “http://80-circ.ahajournals.org.ezproxyhost.library.tmc.edu/cgi/content/full/107/25/3243?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&searchid=1077043477683—12520&stored_search=&FIRSTINDEX=0&volume=107&firstpage=3243&search_url=http%3A%2F%2Fcirc.ahajournals.org%2Fcgi%2Fsearch&journalcode=circulationaha” \l “R6-130282#R6-130282”} can be detected before the development of angiographically significant plaque formation in the coronary and peripheral vasculature by measuring the response to pharmacological and physiological stressors. Endothelial function not only predicts risk, it also tracks changes in response to therapy (pharmacologic and non-pharmacologic) and alterations in risk factors.
Traditional techniques for assessment of endothelial function are invasive, and include: forearm plethysmography with intra-arterial acetylcholine challenge testing; cold pressor tests by invasive quantitative coronary angiography; and injection of radioactive materials and mapping blood flow by tracing movement of radiation. The invasive nature of these tests limits widespread use, particularly in the asymptomatic population. Non-invasive methods include: measurement of the percent change in diameter of the left main trunk induced by cold pressor test with two-dimensional (2-D) echocardiography; the Dundee step test measuring the blood pressure response of a person to exercise (N Tzemos{HYPERLINK “http://qjmed.oxfordjournals.org/cgi/content/full/95/7/423” \l “FN1”}, et al. Q J Med 95 (2002) 423-429); laser Doppler perfusion imaging and iontophoresis; high resolution B-mode ultrasound to study vascular dimensions (T J Anderson, et al. J. Am. Col. Cardiol. 26(5) (1995) 1235-41); occlusive arm cuff plethysmography (S Bystrom, et al. Scand J Clin Lab Invest 58(7) (1998) 569-76); and digital plethysmography or peripheral arterial tonometry (PAT)(A Chenzbraun et al. Cardiology 95(3) (2001) 126-30).
Of these, brachial artery imaging with high-resolution ultrasound (BAUS) during reactive hyperemia is considered the gold standard method of assessing peripheral vascular function. When implementing BAUS a brief, suprasystolic arm cuff inflation provides an ischemic stimulus. Ischemia reduces vascular resistance in the tissues distal to cuff occlusion, and cuff release is accompanied by a sudden rise in blood flow (reactive hyperemia). The increased blood flow through the brachial artery elicits dilation of the arterial wall. Ultrasound imaging of the diameter of the artery, along with measuring the peak flow, defines endothelial function. However, the BAUS method requires very sophisticated equipment and operators that are only available in a few specialized laboratories worldwide. Thus, despite widespread use of BAUS in clinical research, technical challenges, poor reproducibility, and considerable operator dependency have limited the use of this technique to vascular research laboratories.
Venous occlusion plethysmography evaluates peripheral vasomotor function by measuring volume changes in the forearm by mercury strain gauges during hyperemia. A recent review of plethysmography suggested that this method is poorly reproducible, highly operator-dependent, time consuming, and cumbersome. (Yvonne-Tee, G B, et al. “Noninvasive assessment of cutaneous vascular function in vivo using capillaroscopy, plethysmography and laser-Doppler instruments: its strengths and weaknesses,” Clin Hemorheol Microcirc. 2006; 34(4):457-73. Review.) Tissue doppler imaging or flowmetry of the hand can be employed to continuously show skin perfusion before and after hyperemia using single fiber/point Doppler measurement of flow at finger tip. These techniques are also expensive and limited in availability. Alternatively, peripheral arterial tonometry (PAT) can be used to measure changes in the volume of finger as the indicator of changes in blood flow which in turn reflects changes in the diameter of brachial artery during hyperemia. This method is non-invasive but is not inexpensive and is not conducive to self-administration.
Structural tests that are available include an array of diagnostic tests that directly evaluate the presence or physical effects of atherosclerosis and/or CVD. Such structural tests include carotid intimal-medial thickness (IMT) and plaque measurements by ultrasound, aortic and carotid plaque detection by magnetic resonance imaging (MRI), coronary calcium scoring by CT, and peripheral vascular disease detection by ankle-brachial index (ABI) measurement. These tests are valuable for detection of existing conditions and disease progression but are expensive, difficult to self-administer, not easily repeatable, and lack predictive value of vascular reactivity and early stage atherosclerosis.
A few studies have suggested that some of these structural tests can be used to determine an individual's “vascular” and/or “coronary” age, which can then be used in place of the individual's chronological age, thereby improving cardiovascular risk estimation. (Stein J H et al. “Vascular age: Integrating carotid intima-media thickness measurements with global coronary risk assessment,” Clinical Cardiology 2004; 27:388-392; Enrique F Schisterman et al., “Coronary age as a risk factor in the modified Framingham risk score,” BMC Med Imaging. 2004; 4: 1. Published online 2004 Apr. 26. doi: 10.1186/1471-2342-4-1.) However, even newer data has shown that high coronary calcium scores and/or carotid IMT measures are indicative of existing atherosclerotic cardiovascular disease, so the substitution of a ‘vascular age’ or ‘coronary age’ variable in risk prediction models may not be necessary. Also, structural tests are more beneficial for identification and treatment of existing disease than for primary prevention, as they are only capable of visualizing existing disease when there are already high levels of coronary calcium, IMT, and/or atherosclerosis. An effort of the present invention is to provide a direct and comprehensive assessment of vascular age (both function and structure) during all stages of atherosclerosis to enhance the identification, prevention, and/or treatment of CVD.
Accordingly, existing cardiovascular risk assessments face limitations in detection, treatment, devices, and administration. What is needed is a non-invasive, inexpensive and reproducible apparatus that provides improvement in measurement of risk assessment by combining risk factor, functional, and structural assessments of cardiovascular health.
The disclosures herein relate generally to cardiovascular health conditions. More particularly, the present invention provides a method and apparatus for improving measurements of cardiovascular health status in a given individual. In an embodiment, the present invention provides a comprehensive assessment of cardiovascular health that includes at least two components: 1) risk factor assessment based on epidemiologic studies, and 2) functional status of the individual's vascular system. In an embodiment, structural studies of the individual's vascular system can also be incorporated into a comprehensive assessment of cardiovascular health. In an embodiment, the invention aims to improve detection, treatment, devices, and administration of cardiovascular risk assessment.
In one embodiment of the present invention, systems and protocols for generating a combined relative risk of underlying vascular disease are provided. According to the system and method, 1) results of risk factor testing and traditional epidemiologic risk factor questioning are entered into a computational dataset, 2) functional assessments of the vascular system are performed on an individual, 3) values obtained from the functional assessments are entered into the computational dataset for the individual, and 4) a functional and epidemiologic risk factor combined relative risk is computed and reported for the individual. If structural data are available, this data is further added to the dataset to compute a combined comprehensive relative risk of vascular disease. Optionally, and if structural data does not exist for the individual, and largely dependent on the functional and epidemiologic relative risk score, one or more structural assessments are performed and the data entered and computed. In an embodiment, combining cardiovascular assessment results can provide better detection of cardiovascular risk than any of the cardiovascular assessments alone.
In one embodiment, the present invention provides a modular measurement apparatus. The apparatus can have the following features: a central processing unit (CPU) and monitor and printer; resident graphical user interface (GUI) application residing in the CPU; a cuff management module (CMM) to control and receive data from pneumatic cuffs; a blood testing module to control and receive data from a blood testing interface, and a Digital Thermal Monitoring (DTM) module to control and receive data from one or more temperature probes; and may include one or more optional Doppler and data acquisition (DAQ) modules to control and receive data from one or more Doppler probes in order to measure ABI, TBI, TFI, PWV, PWF, and/or DFW. In preferred embodiments the modular apparatus will include a console to house the modules and will preferably provide a compact solution for the integrated assessment modules as well as a housing to carry the CPU, monitor, printer and all above and mentioned components (e.g. Cuffs, Probes, etc) in addition to optional modules. In an embodiment, control for the monitor, printer and all above and mentioned components (e.g. Cuffs, Probes, etc) in addition to optional modules can all be embedded in the CPU. In an embodiment, the apparatus can have capabilities to deliver data from the apparatus to a remote destination. In an embodiment, the method and apparatus can enhance compliance of existing drug regimens of an individual.
Risk factors that are assessed can include one or more traditional and emerging risk factors. In an embodiment, the risk factor computations can be adapted for FRS, diabetes mellitus risk scoring, and/or metabolic syndrome risk scoring. In an embodiment, risk factor computations can be based on information from surveying the behavior of an individual. In an embodiment, the risk factor computations can be based on measurements from cardiovascular testing in addition to survey results.
In one embodiment, testing of vascular reactive capacity of an individual is determined using Pulse Wave Velocity (PWV) and/or Pulse Wave Flow (PWF) analysis for the macrovasculature after challenge, such as with a chemical or physical vasostimulant. In one embodiment, functional capacity of the microvasculature is determined using Doppler Flow Velocity (DFV), Digital Thermal Monitoring (DTM) and/or contralateral vascular reactivity (CLVR), subsequent to vascular challenge. In one embodiment, cardiovascular assessment can include one or more tests or measurements of: BP, total cholesterol, HDL, LDL, triglycerides, PWV, PWF, DFV, DTM, blood thrombogenicity or clotting, ABI, toe brachial index (TBI), toe finger index (TFI), insulin, hemoglobin A1c, liver enzymes, body mass index (BMI), body fat, visceral fat, heart rate variability, electrical impedance, EKG, photoplethysmography (PPG), lipid panels, natriuretic factors and CRP.
In further embodiments, the computer implemented method is optionally further adapted for receiving results from one or more structural assessments on the individual; placing the results of the one or more structural assessments into the computational dataset corresponding to the individual; and computing a combined functional, epidemiologic, and structural relative risk for the individual from the dataset corresponding to the individual. The structural assessments include determination of pathologic changes including one or more of: increased intima medial thickness, atherosclerotic plaque formation and calcium deposits in at least one vascular bed.
In one embodiment the computer implemented method further includes receiving results from one or more serologic assays of a status of circulatory progenitor cells on the individual; placing the results of the one or more serologic assays into the computational dataset corresponding to the individual; and computing a combined functional, epidemiologic, and serologic relative risk for the individual from the dataset corresponding to the individual.
In accordance with an embodiment of the invention, an individual's baseline and reactive functional status are both determined. Baseline functional status is determined in part by measuring blood pressure, which is influenced by the vasculature. Baseline status of the macrovasculature is provided by either or both of Pulse Wave Form (PWF) and Pulse Wave Velocity (PWV). In addition, Digital Thermal Monitoring (DTM) has been determined by the present inventors to provide a powerful measure of neuroreactivity. It has been surprisingly found that when a vascular challenge is applied to a target body such as an arm, the corresponding contralateral remote body reacts as instructed by the neurovasculature. Thus, if blood is occluded from a right arm (target body), a normal neurovasculature senses the need for greater perfusion and directs increased blood flow in the contralateral left arm (remote body). If the individual has a healthy microvasculature, the neurovascular instruction to increase blood flow is effective to induce vasodilation in the contralateral.
In one embodiment of the invention, a modular functional cardiovascular status assessment apparatus is provided including a CPU in electrical communication with and controlling a plurality of cardiovascular function testing modules including a digital thermal monitoring (DTM) module, a cuff management module, a fluid sensing module, a display or recorder, and a Doppler module comprising at least one Doppler sensor. In further embodiments, wherein the DTM module comprises a plurality of temperature sensors; the cuff management module comprises a plurality of blood pressure cuffs and blood pressure detectors; and/or the Doppler module controls a plurality of Doppler sensors. In one embodiment, at least one Doppler sensor is adapted for measurement of Doppler flow velocity. In other embodiments, the Doppler sensor is adapted for pulse wave form (PWF) analysis. In other embodiments, at least two of the plurality of Doppler sensors are adapted to be disposed over a single arterial flow path and at a spaced apart distance sufficient for pulse wave velocity (PWV) measurement and wherein the CPU is programmed to perform PWV analysis. The placement of the sensors may be assisted by the provision of a template or guide for placement of the sensors.
In certain embodiments of the invention, a functional cardiovascular status assessment apparatus is provided that includes a blood pressure cuff in operable association with at least one Doppler sensor array comprising a plurality of Doppler sensors together with a smart Doppler sensor selector that is adapted to monitor signals from each sensor of the array and select the strongest signal providing sensor for signal collection and reporting. The apparatus may further include a computer programmed to perform PWF analysis based on the signal provided by the smart Doppler sensor selector. By computer it is meant a programmable machine.
In one embodiment of the invention, a method of determining a cardiovascular status for an individual is provided including locating a blood flow sensor on a test site on the individual and establishing a stable baseline blood flow reading at the site; providing a local vascular or neurovascular vasostimulant to a body part of the individual that is contralateral to the test site; determining a temperature response to the vasostimulant; and establishing a neurovascular reactivity assessment for the individual based on a blood flow response at the test site. In further embodiments, an additional blood flow sensor is located on the contralateral site corresponding to the test site, the additional blood flow sensor located on a vascular tree directly affected by the local vasostimulant. Blood flow at the site distal from the local vasostimulant is detected by a technique selected from the group consisting of: DTM, skin color, nail capilloroscopy, fingertip plethysmography, forearm plethysmography, oxygen saturation change, laser Doppler flow, ultrasound Doppler flow measurement, near-infrared spectroscopy measurement, wash-out of induced skin temperature, and peripheral arterial tonometry.
Accordingly, the present invention contributes new non-invasive methods and apparatus for cardiovascular assessment as well as important combinations of the cardiovascular assessment with risk factor, functional, and structural analysis.
It is emphasized that this summary is not to be interpreted as limiting the scope of these inventions which are limited only by the claims herein.
The present inventors have developed methods and apparatus for providing a comprehensive individual assessment of cardiovascular health that includes risk factor and functional assessments. In further embodiments, risk factor and functional assessment results are combined with one or more structural assessments as depicted in
In an embodiment, individuals can be assessed for past, present, and future risk. Structural assessments can reveal past or existing cardiovascular conditions, functional assessments can detect present cardiovascular disorders, and epidemiologic risk factor assessment can indicate future cardiovascular risk. Accordingly, in an embodiment, individuals can undergo several assessments and be categorized into overlapping categories of risk. As depicted in
In one embodiment of the present invention, systems and protocols for generating a combined relative risk of underlying vascular disease are provided in accordance with
In one embodiment, the present invention provides a modular measurement apparatus for providing some or all of the assessment modules included in
In preferred embodiments the modular apparatus will include a console to house the modules and will preferably provide a compact solution for the integrated assessment modules as well as a housing to carry the CPU, monitor, printer and all above and mentioned components (e.g. Cuffs, Probes, etc) in addition to optional modules.
In an embodiment, the present invention can provide assessments to aid in medication and treatment compliance. Assessments that are provided can indicate whether or not a patient is adhering to their drug regimen. Anthropometric and/or fluid measurements that can aid in drug compliance include but are not limited to: BMI, body fat level, visceral fat, subcutaneous fat, electrical impedance measures, heart rate variability, glucose tolerance, fasting plasma glucose, blood insulin levels, HDL cholesterol, and fasting plasma insulin. In an embodiment, remote reporting of measurements can be possible wherein assessment results can be sent to a data management center that is in communication with the CPU of the present invention. In an embodiment, the remote data management center can monitor and analyze the reported results and communicate back to the CPU to provide recommendations and/or alterations of medical treatment such as dispensing and/or alterations of drug prescriptions. In an embodiment, the data management center can link together a network of cardiovascular professionals to remotely monitor reports of a patient's cardiovascular assessment. Accordingly, cardiovascular risk management can be provided outside of a hospital setting. For example, cardiovascular assessments as administered by the present invention can be performed not only in clinical and research settings, but also commonplace locations such as cafes, restaurants, retail shops, homes, and/or any place suitable for the compact and portable housing.
Resident GUI Application: Software will be the primary component of the device that will allow the user to use each of the modules. This software will communicate with and manage each module. Preferably it will provide the user with an attractive and easy to use Graphical User Interface (GUI) to perform the tests. This software will also direct storage of the acquired data into a local database. In one embodiment, a web component is included able to transmit the data over the internet and store it into the mother database. The Resident GUI Application (
Cuff Management Module (CMM): The Apparatus will preferably include a Cuff Management Module (CMM) that will be responsible for enabling reactive hyperemia, blood pressure, ABI, TBI, TFI, and other suitable tests using the occlusion principle. In one embodiment, occlusion will be fully automated to perform the test at an on-demand or pre-programmed basis. In an embodiment, the deflation rate of the cuffs can be managed to allow for the desired deflation rate. For example, cuff deflation can be controlled to be sudden, linear, and/or staggered by the CMM. In an embodiment, this module will also incorporate data reception and transmission capabilities so that remote monitoring and data gather operations are possible. An embodiment for a CMM controller can be configured for cuff inflation and deflation, data storage, power, and interfacing as depicted in the block diagram of
One embodiment of the CMM will have the following features:
In an alternative embodiment, the CMM comprises a plurality of cuffs, for occluding blood flow from the vessel of interest (e.g. arm, finger, ankle, etc) and adapted to measure blood pressure.
In one embodiment, the CMM module includes at least two cuffs similar to those employed in blood pressure measurement—placed at the extremities of the patient's limb together with associated control mechanisms. The two cuffs together serve to provide occlusion in the intervening segment. The module will respond to commands from a host device. The two cuffs, say A and B, will be capable of being inflated and deflated simultaneously or independently. The occlusion pressures and duration will be programmable. Inflation will be achieved by energizing a solenoid valve which will actuate the cuff bands. At the upstream cuff A, a pressure sensor will monitor the applied pressure and regulate it using a system of micro-pumps and vent (pressure-release) valves. The downstream cuff B will sense the upstream as well as local pressures and control the applied pressure using a separate system of micro-pumps and vent valves. Micro-chip controller timers will ensure occlusion for the programmed period of time. Deflation will be achieved by simple de-energizing the solenoid.
In a preferred embodiment, system redundancy is included to eliminate single points of failure and ensure safe operation. The safety sub-system—comprising an independent system of solenoids, micro-pumps, vent valves and a micro-chip—will prevent over-pressurization or inflation beyond a certain length of time. Pressure and time thresholds will be set in firmware so that they can be overwritten by host commands. The safety sub-system must be energized in order for the primary pressurization system to function. In the event of secondary system failure, the entire occlusion system will vent to atmospheric pressure and thereby prevent occlusion. The two micro-chips will monitor each other's health, so that both systems will need to be healthy for the CMM to work.
The CMM will be controllable (hosted) by a PC or a carrier board. The host system will be responsible for providing control signals (using standard serial communication technologies) and 12 VDC or other suitable power supply. During normal use, the CMM will be hosted by the carrier board, whereas during testing and firmware upgrades the PC interface will provide greater ease of use.
Cardiovascular Risk Factor Assessment: In one embodiment, comprehensive vascular status of the patient is determined by considering the results of cardiovascular risk factor testing and surveying together with functional macro, micro and neurovascular tests detailed herein. Suitable risk factor considerations can include assessments of traditional and/or emerging risk factors. For example, considerations of cardiovascular risk can include assessments of: age, sex, hypertension (treated or untreated), diabetes, BMI, body fat level, visceral fat, subcutaneous fat, electrical impedance measures, heart rate variability, glucose tolerance, fasting plasma glucose, blood insulin levels, blood pressure, total cholesterol, HDL cholesterol, LDL cholesterol, and fasting plasma insulin, as well as whether or not the patient is a smoker. The results of each assessment are entered into an individual database for the patient and a combined relative risk factor can be calculated.
In an embodiment, risk factor assessments can include any suitable results to compute known risk scoring protocols, such as those for the Framingham Risk Score (FRS) and/or metabolic syndrome. For example, assessments by surveying age, sex, smoking status, diabetes, and hypertension along with cardiovascular testing results of blood pressure, total cholesterol, and HDL can be combined to calculate a FRS. In an embodiment, any suitable risk scoring protocols can be computed, including but not limited to: FRS, Adult Treatment Panel III (ATP III), Prospective Cardiovascular Munster Heart Study (PROCAM), Systematic Coronary Risk Evaluation (SCORE), United Kingdom Prospective Diabetes Study (UKPDS), Reynolds Risk Score, Homeostasis Model Assessment (HOMA), European Society of Cardiology, European Society of Atherosclerosis, European Society of Hypertension, British Regional Heart Study, Sheffield Coronary Risk Tables, General Rule to Enable Atheroma Treatment (GREAT), Dundee Coronary Risk-Disk, National Heart Foundation of New Zealand Guidelines, West of Scotland Cardiovascular Event Reduction Tool, and Joint British Recommendations on Prevention of Coronary Heart Disease in Clinical Practice.
In an embodiment, calculated risk scoring can be combined with other institutional guidelines for assessment and treatment of cardiovascular risk factors. Any suitable guidelines that can be combined with risk scores can be used for treatment, including but not limited to guidelines by major cardiovascular professional organizations such as the American Heart Association (AHA), American College of Cardiology (ACC), National Cholesterol Education Program (NCEP), and Joint National Committee (JNC). For example, as shown in
Blood Pressure and Blood Testing Assessments: In an exemplary embodiment, the invention includes a measure and record of the blood pressure of the subject. In an embodiment, blood pressure measurements can be any that are suitable and well known in the art. In one embodiment, the blood pressure of the subject is measured using Korotkoff sounds or oscillometric methods. In an alternate embodiment, blood pressure measurement is implemented by measuring radial artery waveforms to calculate systolic, diastolic and mean pressures. In alternative embodiments, the blood pressure of the subject is measured using fingertip blood pressure, wrist blood pressure. The blood pressure of the subject can be conveniently measured at one or more times including before, during, and after the provision of a vasostimulant. In an embodiment, blood pressure can be reported to a remote location through the internet. For example, a patient can take their own blood pressure at home and upload information to a website that stores the information so that a physician can make an evaluation.
In an embodiment, the invention includes testing and measurement of various fluid markers of cardiovascular health. In an embodiment, assessment and testing of cardiovascular health can include blood interface tests for blood, serum, and/or fluid markers, including but not limited to: total cholesterol, HDL, LDL, triglycerides, kinases, troponins, insulin, hemoglobin A1c, liver enzymes, lipid panels, natriuretic factors, and CRP. For example, a lipid panel can measure lipids and fats in the blood. Excessively high values may lead to CAD, heart attack, and stroke. In an embodiment, a lipid panel can measure total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, the ratio of total cholesterol to HDL, and the ratio of LDL to HDL. Further, evidence of insulin resistance can lead to metabolic syndrome and Type 2 diabetes. Hemoglobin A1c is a subtype of hemoglobin in which glucose is bound to hemoglobin A. Diabetes detection can be possible because, in non-diabetic persons, the formation, decomposition and destruction of glycosylated hemoglobin can reach a steady state. Even further, liver function enzymes can include measurements of albumin, various liver enzymes (ALT, AST, GGT and ALP), bilirubin, prothrombin time, cholesterol and total protein. These blood tests can be performed at the same time and provide information on liver functionality. In an embodiment, blood, serum, and/or bodily fluids can be extracted and tested by any method and/or apparatus that is suitable and well known in the art. In an embodiment, blood can be extracted manually by lancet prick and manually placed on testing strips as is well known in the art. In an embodiment, blood can be automatically extracted and removed for further testing.
In an embodiment, home cholesterol blood testing devices that are well known in the art can be provided. In an embodiment, they can measure only total cholesterol. In an embodiment, others can measure total cholesterol and high-density lipoprotein (HDL) or “good” cholesterol. In an embodiment, they can measure low-density lipoprotein (LDL) or “bad” cholesterol, HDL cholesterol and triglycerides (blood fats). The tests are performed by a prick of a finger with a lancet to get a drop of blood. Then the drop of blood is put on a piece paper that contains special chemicals. The paper changes color depending on how much cholesterol is in the blood. Some testing kits use a small machine to display the amount of cholesterol in the sample.
In an embodiment, the importance of the coagulation system in the outcome of plaque complications also is emphasized in the present invention. As explained in a recent article, blood borne factors can play a major role in thrombus propagation. (Naghavi et al., From Vulnerable Plaque to Vulnerable Patient: A Call for New Definitions and Risk Assessment Strategies: Part II Circulation 108, 1772-1778). Extensive atherosclerosis may be associated with increased blood thrombogenicity, but the magnitude of thrombogenicity varies from patient to patient, and unstable plaques are much more thrombogenic than stable ones. Thrombogenicity refers to the tendency of a material in contact with the blood to produce a thrombus, or clot. It not only refers to fixed thrombi but also to emboli, thrombi which have become detached and travel through the bloodstream. Thrombogenicity can also encompass events such as the activation of immune pathways and the complement system. All materials are considered to be thrombogenic with the exception of the endothelial cells which line the vasculature. Accordingly, several anti-platelet medical therapies and drugs have become available to physicians providing anti-platelet care. In an embodiment, blood thombogenicity measurements can provide data to individualize assessment of the blood thrombogenicity and/or anti-platelet care of a patient. In an embodiment, blood thrombogenicity measurements can be any that are suitable in the art for the invention as described herein. In an embodiment, blood thrombogenicity measurements can be performed by any suitable sonic and/or light based technologies that are capable of platelet aggregation measurements as described herein.
Ankle Brachial Index (ABI) Module: In one embodiment of the invention, a module is provided for ankle brachial index (ABI) determination. ABI is a useful test to assess lower extremity arterial perfusion. The ABI is particularly useful in defining the severity of Peripheral Vascular Disease (PVD), also known as peripheral arterial disease (PAD). PVD affects more than 8-10 million Americans and is a risk marker for coronary disease, cerebrovascular disease, aneurysmal disease, diabetes, hypertension, and many other conditions. Indeed, patients with documented PVD have a four- to six-fold increase in cardiovascular mortality rate over healthy age-matched individuals. However, fifty percent of people with PVD are asymptomatic.
The Modular Apparatus of the present invention is adaptable for ABI determination. Flow detection for determination of the ABI is traditionally performed using continuous wave Doppler. Thus, one or more of the Doppler probes, as depicted in
In one embodiment of the invention, a combined blood pressure cuff and flow sensor array is utilized wherein the flow sensor array disposed on the inside of the cuff, such as that depicted in
Modular Cardiovascular Functional Assessment: In accordance with the present invention, measurement of the functional status of both the microvasculature and the macrovasculature is provided in addition to methods and apparatus for determination of neurovascular status. It is believed that the endothelial function and vascular reactivity of resistant vessels (microvasculature) can be determined by measuring changes in blood flow during a reactive hyperemia test. It is also known that changes in the diameter of non-resistance arteries subsequent to shear stress induced by increased flow reflect the endothelial function and vascular reactivity of conduit vessels (macrovasculature). Thus vascular reactivity measured during a reactive hyperemia procedure has become an established method of detecting both endothelium dependent and independent mechanisms involved in the physiologic and pathologic response to ischemia involving both the micro and macrovasculature. Vascular biology studies have shown involvement of multiple biochemical pathways in both micro and macro vascular reactivity including nitric oxide and prostaglandin pathways.
Referring now to
Digital Thermal Monitoring (DTM): Certain of the present inventors have developed novel methods and apparatus to determine the vascular reactivity based on a measured response of the vasculature to reactive hyperemia utilizing continuous skin monitoring of inherent temperature on a digit distal (downstream) to an occluded arterial flow. By inherent temperature it is meant the unmodified temperature of the skin as opposed to measurement of the dissipation of induced temperature. This principal and technique has been termed Digital Thermal Monitoring (DTM). See WO 05/18516 and U.S. patent application Ser. No. 11/563,676, the disclosures of which are incorporated herein by reference.
It is well known that tissue temperature is a direct result of blood perfusion, but other parameters also contribute. These parameters can be classified as:
Different embodiments of this invention characterize and quantify the effect of different factors that affect the baseline temperature and temperature response observed after brachial artery occlusion.
DTM is typically implemented by measuring temperature changes at the fingertips during reactive hyperemia induced by transient arm-cuff occlusion and subsequent release. A normal reactive hyperemia response, i.e. increased blood flow after occlusion, is manifest by increased skin temperature over the baseline temperature established prior to occlusion. In an exemplary embodiment, DTM is implemented by having a subject quietly situated, such as by sitting or laying, with the forearms supported. DTM probes are affixed to the index finger of each hand. The digital thermal response during and after brachial artery occlusion is recorded and the resulting thermographs indicate temperature change during the procedure.
Since endothelial function is a systemic property, a localized measurement in a readily accessible location of the human body (such as the digits) can provide an accurate assessment of vascular health in physiologically critical locations such as the coronary arteries. DTM is thus being developed as a new surrogate for endothelial function monitoring that is non-invasive, operator-independent (observer-independent) and is sufficiently straightforward to be readily implemented across the population to assess individual vascular function. Preliminary studies have shown that digit temperature correlates significantly with brachial artery reactivity and thus provides a novel and simple method for assessing endothelial function. Further studies have shown that DTM can discriminate individuals with established CHD or high risk of future CHD (as measured by Framingham, Diabetes, and Metabolic Risk Scores) from normal and low-risk individuals, as discussed further herein.
In one method, a sensitive digital thermal monitoring (DTM) device, similar to that depicted in
Any skin temperature sensor design suitable for the invention as described herein can be used. For example,
TR and NP indicate the vasodilatory capacity of the vascular bed (small arteries and micro-vessels) and subsequent hyperemia induced brachial artery dilation. TR specifically denotes the ability of the arterial bed to compensate for the duration of the ischemia and to create an overflow (hyperemia) above the baseline level. Given a good vasodilatory response and constant room temperature one would expect a positive TR. The higher the TR, the higher the vasodilatory response of the arterial bed. TR close to zero indicates a lack of strong vasodilatory response and negative TR is likely to represent a vasoconstrictive response. NP and TR largely overlap and both show similar trends with TR being a more sensitive marker of overflow (hyperemia response) and NP showing additional factors that affect TF (such as neuroregulatory effect and basal metabolic rate). Factors as TTF, TTR and area under the curve are expected to provide additional insights into the response to the ischemia challenge test. Further, in an embodiment, one or more correction factors to correct for physical and/or mechanical variations can be provided to improve measurement of the purely physiological response.
A simplified set of DTM values can be utilized as depicted in
In one embodiment, the DTM module controller will be an analog data acquisition printed circuit board (PCB). It will be used in DTM testing to monitor temperature changes in the fingers due to blood occlusion. It will be interfaced with the temperature probes. It will gather temperature data, convert it into a digital format and transmit it to an external device. This module is designed to perform various functions including the following:
In a preferred embodiment, the DTM comprises a main control unit (MCU), a power supply for the temperature sensors (RTDs), an ambient temperature sensor, a temperature acquisition unit and a data storage unit. The entire module is controlled by a host device, either be a PC or a carrier board. The host can communicate with the module using standard serial communication technologies.
Control will be achieved using a well defined set of commands, such as initialize, get temperature, reset, calibrate, etc. Upon receiving an initiate command, the data acquisition unit reads temperatures from a plurality of RTD sensors. A large number of sensors may be used to attain a high signal-to-noise ratio using filtering and averaging techniques. The DTM constantly monitors and filters the temperature readings from all the sensors. To retrieve the measurement, the host is expected to send read commands at a fixed frequency for the duration of the test; a faster internal sampling frequency will be employed to ensure adequate data for filtering purposes. In one embodiment, the DTM returns an 8-bit status code indicating the health of the device and the measurements. In a preferred embodiment, to further attain high accuracy sensor self-heating will be limited by applying a sensor voltage bias to each sensor for a short duty cycle. In one embodiment a boot-loader mechanism is be provided to enable new versions of firmware to be installed via the PC interface mechanism.
In one embodiment of the invention, changes in skin temperature before, during, and after an ischemia challenge are measured and related to the underlying vascular, metabolic, and neuroregulatory functions of the tissues. In one embodiment, repeated measurement of the temperature response as well as testing temperature responses in multiple vascular beds including the arm, forearm, wrist, and both legs provides a more comprehensive assessment. For example, the AV shunts in digital capillaries can affect distal microvessel resistance and therefore the flow measurement or response to ischemic challenge can vary depending on the opening of these AV shunts as a consequence of sympathetic drive. One way to measure the AV shunt effect is to simultaneously measure temperature at the distal finger tips as well as proximal to the finger tip such as on the wrist or forearm. By comparing temperature changes in these two locations, one can create a differential signature plot that indicates the activity of the sympathetic nervous system and/or AV shunting. The modular design of the present apparatus is able to monitor and control a plurality of skin temperature measurement devices.
DTM and BP measurement can be facilitated by an integrated device that provides monitoring of blood pressure in conjunction with a pressure cuff used to provide vascular occlusion as part of a DTM measurement. The combination of BP and DTM is particularly suitable for the management of hypertension. Using different ischemia challenge protocols, one can distinguish between different stages of hypertensive vascular disease. Subjects in later stages of the disease whose vasodilatory capacity is severely reduced may show lower TR. Longer duration of ischemia may distinguish this group with the earlier stages of hypertension where the vasodilatory capacity is relatively high.
Blood pressure measurement, which can be subject to high variability and White Coat effect, has evolved over time into ambulatory monitoring including use outside of the hospital. Similarly, measurement of brachial vasoreactivity, including as measured by DTM, may show marked variations including diurnal, postprandial, positional, exercise and stress related variability. Solutions to control for variability issues include multiple measurements and standardized settings for measurement. A requirement for multiple measurements cannot be met by BAUS, which is a very complicated, cumbersome and expensive measurement. In contrast, DTM has great potential to provide an endothelial function measurement device capable of ambulatory monitoring. Such a device, including combined with blood pressure monitoring device, can provide an excellent tool for screening and monitoring of vascular function at minimum cost.
Contralateral Vascular Response (CLVR): Importantly, the present inventors have found that significant temperature changes in control arms were found in some individuals that are thought to reflect the neuroregulatory response to the cuff inflation and deflation. Thus, in one embodiment, measurements on the contralateral hand to that receiving a vascular challenge are used to establish a vascular, metabolic, and neuroregulatory profile for the patient. The present inventors have surprisingly found that, rather than being considered as “noise” to be discounted or controlled, in certain embodiments of the present invention, measurement of skin temperature on the contralateral hand is utilized to provide important insights into the vascular reactivity profile of the individual.
In contrast to the test hand to which a vascular challenge is applied, for example by occlusion of the brachial artery feeding the test hand, the contralateral hand is also monitored for blood flow changes such as by a fingertip temperature measurement on the corresponding digit of the contralateral hand but without vascular challenge to the vasculature feeding the contralateral hand. Since 85% of skin circulation is thermoregulatory and tightly controlled by the sympathetic system, changes in the contralateral finger temperature can be quite diagnostic. In some patients, the contralateral finger temperature goes up in the inflation phase and declines in the deflation phase. The contralateral finger response reflects both the activity of the sympathetic nervous system but also the ability of both the nervous system and the vasculature to work together to respond appropriately to vascular challenge.
Contralateral vasomotion is believed to show the neurogenic factors involved in the arm-cuff based vascular reactivity test and provides, for the first time, the ability to provide characterization of this influence in different individuals.
Physiologic stimuli such as local pain, pressure, and ischemia are known to create systemic effects mostly mediated by autonomic (sympathic and parasympathic) nervous system. DTM provides a mechanism to correlate primary and secondary autonomic disorders shown by heart rate variability, and orthostatic hypo and hyper-tension in coronary heart disease and a host of other disorders, with the thermal behavior of contralateral finger.
In one embodiment, the body part is a first hand on the subject, and the contralateral body part is a second hand on the subject. In other embodiments, the body part is a first foot on the subject, and the contralateral body part is a second foot on the subject. In an exemplary embodiment, the body part is a finger on the subject, and the contralateral body part is a toe on the subject.
Changes in blood flow in a contralateral body part as a consequence of a vascular stimulus on a corresponding test body part can be detected by temperature sensing instrumentalities including for example with a thermocouple, thermister, resistance temperature detector, heat flux detector, liquid crystal sensor, thermopile, or an infrared sensor. However, changes in blood flow in a contralateral body part as a consequence of a vascular stimulus on a corresponding test body part are not limited to temperature detection but may also be detected by skin color, nail capilloroscopy, fingertip plethysmography, oxygen saturation change, laser Doppler, near-infrared spectroscopy measurement, wash-out of induced skin temperature, and peripheral arterial tonometry.
In an alternative embodiment, vascular responses in the contralateral body part are detected by infrared thermal energy measuring devices such as, for example, infrared cameras. Temperatures before, during, and after vasostimulation, such as may be provided by cuff occlusion, are measured by infrared camera. Infrared (IR) thermography is employed to study vascular health before, during, and after a direct vascular stimulant such as nitrate or cuff occlusion. For example, infrared imaging of both hands or feet during cuff occlusion test (before cuff occlusion, during and post occlusion) using infrared thermography results in a comprehensive vascular and neurovascular assessment of vascular response in both hands or feet.
In an embodiment, the CLVR response from both hands of the same individual can be quantified into one systemic value. For example,
Pulse Wave Velocity (PWV) Module: PWV is a function vascular stiffness & dimensions and because it is modulated by compliance, PWV can be used to assess macrovascular function. PWV is typically defined mathematically as PWV2=Eh/dp, where E is Young's modulus, h is thickness, d is diameter, and p is blood density. PWV measurements utilize spaced apart detectors that essentially compare the time of arrival of a pulse between the spaced apart detectors. PWV can be detected by tonometry, ultrasonography, and oscillometrics. In one embodiment of the invention, PWV is determined by Doppler measurements at two spaced apart sited on a single arterial tree. In one embodiment the spaced apart sites are located essentially at brachial and radial sites to detect changes in PWV in response to increased blood flow induced by reactive hyperemia (similar to FMD).
A set up for measuring pulse wave velocity is depicted in
With a healthy vascular response, the pulse travel time from A to B increases after cuff deflation (indicating the intermediate artery dilatation and slowed pulse wave velocity). Analysis of the data recorded at point A and point B is overlaid as depicted in
Pulse Wave Velocity can also be used to determine vascular function in response to reactive challenge. Reactive hyperemia is defined as hyperemia, or an increase in the quantity of blood flow to a body part, resulting from the restoration of its temporarily blocked blood flow. When blood flow is temporarily blocked, tissue downstream to the blockage becomes ischemic. Ischemia refers to a shortage of blood supply, and thus oxygen, to a tissue. When flow is restored, the endothelium lining the previously ischemic vasculature is subject to a large, transient shear stress. In partial response to the shear stress, the endothelium normally mediates a vasodilatory response known as flow-mediated dilatation (FMD). The vasodilatory response to shear stress is mediated by several vasodilators released by the endothelium, including nitric oxide (NO), prostaglandins (PGI2) and endothelium-derived hyperpolarizing factor (EDHF), among others. A small FMD response is interpreted as indicating endothelial dysfunction and an associated increased risk of vascular disease or cardiac events. See Pyke K E and Tschakovsky M E “The relationship between shear stress and flow-mediated dilatation: implications for the assessment of endothelial function” J Physiol 568(2) (2005) 357-9.
Induction of reactive hyperemia is well-established in clinical research as a means to evaluate vascular health and in particular endothelial function. Typically, a reactive hyperemia procedure is implemented by occluding arterial blood flow briefly (2-5 minutes, depending on the specific protocol) in the arm, by supra-systolic inflation of a standard sphygmomanometer cuff, then releasing it rapidly to stimulate an increase in blood flow to the arm and hand. Reactive hyperemia has been classically measured by high-resolution ultrasound imaging of the brachial artery during and after arm-cuff occlusion. However, the technical difficulties of ultrasound imaging have limited the use of this test to research laboratories. This method is clearly unsuitable to widespread adoption of reactive hyperemia as a test of vascular function. The method is simply inapplicable to evaluation of endothelial function in the context of real life stress inducers.
The present inventors have adapted PWV as a more accessible measurement of FMD using Doppler detection. A baseline PWV measurement is obtained as described above. The procedure is repeated after inflation of a blood pressure cuff for sufficient time to normally induce FMD, followed by release of the cuff and immediate determination of PWV.
In an alternative embodiment, pulse wave velocity is determined not from the velocity of natural pulses but from the velocity of an artificial pulse induced by external distal arterial tapping to create a tapped reverse wave such as described by Maltz J S and Budinger T F. WO2005/079189.
Pulse Wave Form (PWF): Arterial circulation is hemodynamically controlled by the relationship between pulsatile cardiac output and total peripheral resistance, which is modulated by vascular tone, capillary density and the wall thickness to lumen ratio in the media of the microvasculature. To the extent that they are able, the arteriolar and capillary beds provide variable resistance to flow and thereby regulate blood flow to meet the need of the tissues. PWF analysis provides a measure of the stiffness of an artery supplying blood to the body part.
As depicted in
Typically pulse wave form analysis is determined by use of a single Doppler probe. If there is an increase in the diameter of the artery (e.g. induced by reactive hyperemia such as by occlusion of the brachial artery by a blood pressure cuff) this will delay the reflectance (backward) wave which will then increase the overall width, W, of the pulse or decrease its height.
In one embodiment of the invention, a smart Doppler sensor array module is provided that may be employed for PWF or PWF analysis. The smart Doppler sensor array module comprises an array of Doppler probes electrically coupled to a signal selection module that selects input from the probe delivering the strongest signal for recording. By the use of a smart Doppler sensor array, detection of the Doppler pulse is operator and individual anatomy independent. In one embodiment, such as that depicted in
The array may include sensors resonating at different frequencies providing information at different depths through a tissue. The array may further include sensors positioned at different angles for locating a maximum Doppler blood flow velocity. In one embodiment the target cardiovascular system is selected from the group consisting of: carotid, brachial, femoral, aortic and coronary.
Doppler Flow Velocity Measurement (DFV): The present inventors have shown that continuous monitoring of Doppler Flow Velocity (DFV) before, during, and after inflation of a blood pressure cuff over the brachial artery provides measurement of vascular reactivity at either the radial or brachial levels. Methods and apparatus for comprehensive assessment of vascular function are provided by combining temperature changes with changes in peak systolic Doppler velocity measurement by Doppler ultrasonography. This combination of thermography and Doppler ultrasonography is herein termed “thermodoppler.” For example, and with an apparatus such as that as depicted in
The results of a DFV response 40a is depicted in
The results of this analysis (peak of the flow rebound, the slope of decline to baseline and the area under the curve) showed variability between individuals. DFW thus provides a measure of microvascular reactivity because it is the resistance vessels that establish whether flow can increase after release of the blood pressure cuff.
The Doppler flow velocity curve can be used as a non-invasive correlate of metabolic and biochemical factors affecting the distal microvascular resistance (e.g. lactate concentration, pH, calcium ion, etc. In summation, the curve can be calibrated to study, non-invasively, factors affecting vascular health.
Further Functional Testing Modalities: In an embodiment, a risk score measurement utilizing blood testing, an ankle-brachial blood pressure index, and a DTM measurement can be determined for the subject. Further, specialized devices for performing one or more of the following techniques known to those of skill in the art may be added as diagnostic modules: skin color determination, nailbed capilloroscopy, ultrasound brachial artery imaging, forearm plethysmography, fingertip plethysmography, pulse oximetry, oxygen saturation change, pressure change, near-infrared spectroscopy measurements, peripheral artery tomometry, and combinations thereof. In one embodiment, various measurements of vascular reactivity are determined, weighted and a derivative composite index is determined.
In one embodiment, a combination of treadmill exercise test and one or more functional tests provided herein are designed to be superior to use of the exercise treadmill test alone in predicting the results of a nuclear test.
Serologic Testing Inputs: In one embodiment, the functional vascular status of the patient is considered together with additional diagnosis techniques in order to assess the subject's endothelial function. Additional diagnosis techniques may include one of more quantitative tests of the numbers and function of endothelial progenitor cells and related particles, such as endothelial derived microparticles in the peripheral blood. For example,
Other serologic tests include quantitative assays for one or more of the following factors: VEGF, VCAM1, ICAM1, Selectins such as soluble endothelium, leukocyte, and platelet selectins, VWF, CD54, c-reactive protein, homocysteine, Lp(a) and Lp-PLA2. Further assays that may be employed include determination of: urinary albumin, serum fibrinogen, IL6, CD40/CD40L, serum amyloid A, PAI-1 test, t-PA test, homeostasis model assessment, white blood cell count, Neutrophil/lymphocyte ratio, platelet function tests, plasma and urinary level of asymmetrical (ADMA) and symmetrical (SDMA) dimethylarginine, exhaled nitric oxide, myelo-peroxidase (MPO), endothelin-1, thrombomodulin, tissue factor and tissue factor pathway inhibitor, markers of inflammation such as, for example, granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage chemoattractant protein-1 (MCP-1), nitric oxide and its metabolites nitrates and nitrites, nitrosylated proteins, markers of oxidative stress including but not limited to free radical measurements of the blood or through the skin, TBAR, and/or extra cellular super oxide dismutase activity, and combinations thereof.
Further Vasostimulants: In alternative embodiments, in lieu of, or in addition to, using cuff occlusion for providing a vasostimulant, other vasostimulants may be employed while measuring both macro and micro vascular responses, and/or neurovascular responses: chemical vasostimulants such as nitroglycerin or transdermal substances, sympathetic mimetic agents, para-sympathetic mimetic agents, acetylcholine, vasodilating nitrates such as, for example, nitroprusside or glyceryl trinitrate, inhibitors of endothelium-derived contracting factors such as, for example, ACE inhibitors or angiotensin II receptor antagonists, cytoprotective agents such as, for example, free radical scavengers such as superoxide dismutase endothelium dependent agents such as, for example, acetylcholine, and/or endothelium independent agents such as, for example, nitroprusside or glycerin trinitrate, psychological vasostimulants such as aptitude tests, mental arithmetic, visual stimulation, physiological vasostimulants such as the Valsalva maneuver, a tilting test, physical exercise, whole body warming, whole body cooling, local warming, local cooling, contralateral handgrip, contralateral hand cooling, and painful stimuli such as, for example, nailbed compression, and a variety of others.
In an exemplary embodiment, the chemical vasostimulants may stimulate the vessel either through the endothelium or bypass the endothelium and directly affect the muscular part of the vessel wall, which is endothelium independent. In an exemplary embodiment, the vasostimulant may be, for example, a neuro-vasostimulant, a neurostimulant, a vasoconstrictor, a vasodialator, an endothermal layer stimulant, or a smooth muscle cell or medial layer stimulant. In an exemplary embodiment, a neuro-vasostimulant may include, for example, having the subject drink a glass of ice water.
Controlled Conditions: Skin microcirculation is divided into nutritional circulation and thermoregulatory circulation. It is well known that the thermoregulatory circulation that accounts for the majority of fingertip skin circulation is tightly controlled by autonomic nervous system. The thermoregulatory control mechanism is effected through arteriovenous shunts that bypass pre-capillary part of the side to the post-capillary of venous side. These networks of small arterioles are highly innervated and in cases of sympathetic stimuli such as mental stress and cold exposure, their contraction increase distal resistance and results in rerouting blood flow to AV shunts. This phenomenon explains cold fingers in fingertips during adrenergic stress. The side effect of this phenomenon on digital thermal monitoring of vascular reactivity (DTM) can be significant. However, such a “noise” effect is not limited to digital thermography. Indeed, studies have shown that BAUS is similarly affected by such sympathetic conditions. To minimize the effects of these conditions on endothelia function measurement, the International Task Force for Brachial Artery Reactivity has proposed certain guidelines for subject preparation and BAUS measurement to standardize the technique. Similar considerations can be exercised for DTM. However, the fact that this technique is much more simplified and can be repeated easily (potentially at the comfort home and ambulatory monitoring), makes it possible to have a more accurate assessment of endothelial function in those with hyperadrenergic conditions.
Structural Testing Inputs: In one embodiment, comprehensive vascular status of the patient is determined by considering the result of the cardiovascular tests detailed herein together with additional structural diagnosis techniques as depicted in
Clinical Utility—Relationship Between DTM and Cardiovascular Risk: Population-based cardiovascular risk calculators, e.g. Framingham Risk Estimation (FRE) are valuable in predicting long term future cardiovascular events in populations, but cannot accurately measure the status of vascular health in individuals. The present inventors developed DTM during reactive hyperemia as a complementary vascular function test to improve cardiovascular risk assessment. The ability of DTM to identify individuals with known coronary heart disease (CHD), and its correlation with FRE in a community setting was assessed. 133 individuals (51% male; 54±10 years; 19 with known CHD) underwent DTM measurements before, during, and after 2 minutes of upper arm cuff occlusion. The results are depicted in
Relationship Between DTM, FRS, and Metabolic Syndrome: Endothelial dysfunction is the first stage of the atherosclerosis process and results in insulin resistance, metabolic syndrome (MS) and diabetes (DM). The ability of DTM, based on reactive hyperemia (RH), to identify metabolic status in asymptomatic at-risk adults was tested.
Study Population and Methods: 233 subjects (62% male, 58+11 yrs, 48% with family history of CHD, 46.1% hypertensive, 53% with hypercholesterolemia, 19% diabetic, and 38.6% smokers) were studied. Each underwent DTM during and after 5 min supra-systolic arm cuff inflation, CACS and FBS, Lipid profile, blood pressure, height, weight, waist and hip circumference measurements. Initial fingertip temperature at cuff inflation (TMP), lowest temperature (nadir) observed after cuff inflation (TMPmin), and indices of thermal recovery after cuff release (temperature rebound over baseline (TR) and slope of recovery) were measured.
Results: Room temperature was 74.6+2.7° F. TMPi (90±4° F.) and TMPmin% (95.8±1.3° F.) were similar in three groups (p>0.7). TR % was (1.5±0.25° F.) in 94 with RRE<10% vs. (0.8±0.15° F.) in 75 with PRE>20% (p=0.01). 106 subjects with neither condition had higher TR % (2±0.23° F.) than 81 with MS (0.93±0.17° F.) and DM (0.91±0.2° F.) (p=0.001), suggesting reduced vascular reactivity in MS and DM and increasing PROCAM 10 year CHD risk (PRE %). After adjustment for age, gender and other CV risk factors by logistic regression, TR % remained significantly lower in the those with MS and DM than neither one (odds ratio=0.62 (95% CI 0.43-0.89, p=0.001)) and (odds ratio=0.68 (95% CI=0.52-0.88, p=0.003)) respectively also in PRE≧20% and CAC≧75% than PRE≦10% and CAC<10 (odds ratio=0.63 (95% CI=0.42-0.95, p=0.02)) and (odds ratio=0.57 (95% CI=0.35-0.92 p=0.01)) respectively. The data indicate that thermal/vascular function in the fingertip is associated inversely with presence of MS and DM, PROCAM, severity of CAC, and FRE in asymptomatic adults.
Relationship Between DTM and Coronary Calcium Score: Comprehensive assessment of cardiovascular health must include measurement of risk factors as well as structural and functional evaluation of the vasculature. The ability of DTM to identify asymptomatic high risk individuals objectively defined by coronary artery calcium score (CACS)>75th percentile and 10y Framingham Risk Estimate (FRE)>15% was tested in the same population as the above mentioned Metabolic Syndrome study.
Results: TMPi and TMPmin were not significantly different in high risk versus low risk groups (90.3±4.03 vs. 90.4±4.3° F., P>0.9) and (86.6±3.5 vs 86.4±3.8° F., P>0.6) respectively. In 105 subjects with FRE<5%, TR % was 1.57±0.23 vs. 0.84±0.14 in 52 with FRE>15% (p<0.01). TR % was also higher in 109 subjects with CACS<10 (1.82±0.19) vs. 62 with CACS≧75th percentile (1.09±0.22) (p<0.01), suggesting reduced vascular reactivity in both higher risk cohorts. After adjustment for age, gender and other traditional risk factors by logistic regression, TR % remained significantly lower in those with CACS≧75% than CACS<10 (odds ratio 0.57, 95% CI=0.35-0.92, p=0.02). Also TR % remained significantly lower in those with FRE≧15% than FRE≦5% (odds ratio 0.57, 95%=CI 0.35-0.92, p<0.02) and those with metabolic syndrome than healthy population (odds ratio=0.62, 95% CI=0.43-0.89, P<0.001). The data indicate that vascular function measured by DTM during a 5-minute cuff occlusion reactive hyperemia test is inversely associated with the burden of atherosclerosis and risk factors of atherosclerosis as measured by CACS and FRE respectively.
Further,
It is understood that variations may be made in the foregoing without departing from the scope of the disclosed embodiments. Furthermore, the elements and teachings of the various illustrative embodiments may be combined in whole or in part some or all of the illustrated embodiments. Although illustrative embodiments have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure and in some instances, some features of the embodiments may be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the embodiments disclosed herein.
This application is a continuation-in-part of and claims priority to U.S. application Ser. No. 11/690,122 filed Mar. 22, 2007, which in turn claims priority to U.S. Provisional Application Ser. No. 60/784,874, filed Mar. 22, 2006, the disclosures of which are incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 60784874 | Mar 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11690122 | Mar 2007 | US |
| Child | 11963681 | US |
