Patent Application
20080281305
This document relates generally to implantable medical devices and particularly a system for relieving angina symptoms using an implantable device that emits light to an ischemic region.
The heart is the center of a person's circulatory system. It includes an electro-mechanical system performing two major pumping functions. The left portions of the heart draw oxygenated blood from the lungs and pump it to the organs of the body to provide the organs with their metabolic needs for oxygen. The right portions of the heart draw deoxygenated blood from the body organs and pump it to the lungs where the blood gets oxygenated. These pumping functions are resulted from contractions of the myocardium. In a normal heart, the sinoatrial node, the heart's natural pacemaker, generates electrical impulses that propagate through an electrical conduction system to various regions of the heart to excite the myocardial tissues of these regions. Coordinated delays in the propagations of the electrical impulses in a normal electrical conduction system cause the various portions of the heart to contract in synchrony to result in efficient pumping functions.
Cardiac ischemia is a condition in which the myocardium is deprived of adequate oxygen and metabolite removal due to reduced or interrupted blood supply caused by constriction of a blood vessel such as a coronary artery. In a patient having cardiac ischemia due to obstruction to blood flow in a coronary artery, angina (angina pectoris, or cardiac pain) is likely to develop when the blood flow fails to meet the metabolic need of the heart. Angina is also an indication that the cardiac ischemia may develop into myocardial infarction (MI). MI is the necrosis of portions of the myocardial tissue. The necrotic tissue, known as infarcted tissue, loses the contractile properties of the normal, healthy myocardial tissue. Consequently, the overall contractility of the myocardium is weakened, resulting in an impaired hemodynamic performance. Following an MI, cardiac remodeling starts with expansion of the region of infarcted tissue and progresses to a chronic, global expansion in the size and change in the shape of the entire left ventricle. The consequences include a further impaired hemodynamic performance and a significantly increased risk of developing heart failure, as well as a risk of suffering recurrent MI.
Therefore, there is a need to treat cardiac ischemia, including the associated angina symptoms.
An implantable medical device includes a light emitting circuit incorporated into an intravascular stent. The light emitting circuit emits a light to an ischemic region to relive angina symptoms associated with ischemia.
In one embodiment, the light emitting circuit includes a light source, a power supply circuit, and an implant controller. The light source emits a light having characteristics suitable for reliving the angina symptoms. The power supply circuit produces a power supply signal suitable for powering the light source. The implant control circuit controls the emission of the light from the light source during a light emission duration.
In one embodiment, a method for emitting a light to an ischemic region to relieve angina symptoms is provided. A light emission duration is started and timed. A light source is incorporated into an intravascular stent configured to be placed in the ischemic region, and is powered using a power source incorporated into the intravascular stent. The light is emitted from the light source during the light emission duration. The light has characteristics suitable for reliving the angina symptoms.
This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. The scope of the present invention is defined by the appended claims and their legal equivalents.
The drawings illustrate generally, by way of example, various embodiments discussed in the present document. The drawings are for illustrative purposes only and may not be to scale.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description provides examples, and the scope of the present invention is defined by the appended claims and their legal equivalents.
This document discusses a system including an implantable medical device that delivers a light therapy to reduce angina symptoms resulting from ischemia. Examples of known therapies for treating angina symptoms caused by cardiac ischemia include spinal cord stimulation and enhanced external counterpulsation (EECP). Spinal cord stimulation suppresses the cardiac pain, but does not treat cardiac ischemia. EECP is known to treat cardiac ischemia with its angiogenetic effect, but requires a lengthy therapy (five hours per day for sevens days, for example). The present system uses a light emitting circuit incorporated into an intravascular stent. After the intravascular stent is placed in or near an ischemic region, the light emitting circuit provides for controlled emission of a light having characteristics suitable for reliving the angina symptoms. This therapy provides for pain relief and angiogenesis using relatively short periods of delivery. The angiogenetic effect has the potential of eventually eliminating the cause of the angina symptoms.
External system 120 allows control of the delivery of the light therapy from implantable medical device 110. Telemetry link 115 provides for power and/or data transmission from external system 120 to implantable medical device 110. In one embodiment, telemetry link 115 uses a carrier signal to transmit power to implantable medical device 110 for the operation of the light emitting circuit, and the carrier signal is modulated for the date transmission. Examples of the carrier signal include magnetic signal and ultrasonic signal. In another embodiment, telemetry link 115 uses a carrier signal for power transmission and another carrier signal modulated for data transmission. For example, telemetry link 115 uses a magnetic or ultrasonic signal for power transmission and an electromagnetic signal modulated for data transmission. In another embodiment, telemetry link 115 also provides for data transmission from implantable medical device 110 to external system 120, such as for transmission of data representative of operation status of implantable medical device 110 and/or one or more signals sensed by implantable medical device 110.
Intravascular stent delivery catheter assembly 232 includes a catheter shaft 234, which has a proximal end 236 and a distal end 238. Intravascular stent delivery catheter assembly 232 is configured to advance through the patient's vascular system over a guide wire 242. Intravascular stent delivery catheter assembly 232 as illustrated in
Artery 207 as shown in
Light emitting circuit 250 is shown in
In the illustrated embodiment, PLED 754 includes a transparent substrate 755 (such as a glass layer), a transparent anode 756 (such as an indium tin oxide layer) on transparent substrate 755, a hole transporting layer 757 on transparent anode 756, a light emitting polymer 758 on hole transporting layer 757, and a cathode 759 on light emitting polymer 758. PLED 754 emits a light for reliving the angina symptoms when a voltage at a specified level is applied using a conductor 760 connected to transparent anode 756 and another conductor 761 connected to cathode 759. In one embodiment, PLED 754 is mounted on a portion of intravascular stent 730, with cathode 759 in contact with a portion of the mesh of intravascular stent 730.
Light source 852 is configured for placement in a patient having angina symptoms to deliver the light therapy to an ischemic region in the patient's body. The light has characteristics suitable for reliving angina symptoms. In one embodiment, light source 852 is configured to emit a light having a wavelength between 600 nanometers and 1,000 nanometers, with approximately 800 nanometers being a specific example. Such a light has been experimentally shown to result in expression of vascular endothelial growth factors (VEGF) that may eventually trigger angiogenesis in the ischemic area. In one embodiment, light source 852 emits such a light in a gene therapy to enhance expression of light-sensitive promoters.
Light emission controller 862 controls the emission of the light from light source 852 and includes a light emission initiator 864 and a light emission timer 866. Light emission initiator 864 produces a light initiation signal to start a light emission duration during which light source 852 emits the light. In one embodiment, light emission initiator 864 receives a light emission command and produces the light initiation signal in response to the light emission command. In another embodiment, light emission initiator 864 is programmed to produce the light initiation signal according to a specified schedule, such as on a periodic basis using a programmed period. In one embodiment, the period is programmable between 1 minute and 72 hours. In one embodiment, light emission initiator 864 is programmed to produce the light initiation signal when the patient is most likely inactive, such as during normal sleeping time.
Light emission timer 866 produces a light emission signal in response to the light initiation signal. The light emission signal is present during the light emission duration. In other words, light source 852 emits the light while the light emission signal is present. In one embodiment, the light emission duration is programmable between 10 seconds and 60 minutes.
Light source 1052 represents a specific embodiment of light source 852 and includes one or more LEDs 1054. In one embodiment, LED(s) 1054 include LED(s) in die form suitable for mounting on an intravascular stent. In another embodiment, LED(s) 1054 include PLED(s).
Power supply circuit 1068 represents a specific embodiment of power supply circuit 968. In the illustrated embodiment, power supply circuit 1068 includes a battery 1074, a power converter 1076, and a power receiver 1078. Power receiver 1078 receives the power transmission signal via telemetry link 115. Power converter 1076 produces the power supply signal suitable for powering light source 1052 and implant control circuit 970 using the power transmission signal. In a specific embodiment, power converter includes an AC-to-DC converter and a voltage regulator to convert the power transmission signal (such as a sinusoidal signal or a square-wave AC signal) to a DC signal having a specified voltage. In a specific embodiment, battery 1074 includes a rechargeable battery that is rechargeable using the power supply signal. In another embodiment, power supply circuit 1068 includes only battery 1074, for example, when implantable medical device 910 is intended for short-term use. In another embodiment, power supply circuit 1068 includes only power converter 1076 and power receiver 1078. Light source 1052 emits a light when the power transmission signal is being received via telemetry link 115.
Implant telemetry circuit 1072 receives the power transmission signal. In one embodiment, implantable telemetry circuit 1072 also receives a data transmission signal including, for example, the light emission command that triggers the light initiation signal, the light initiation signal, or the light emission signal, depending on which portions of light emission controller 862 is included in implant control circuit 870, as further discussed below with reference to
In one embodiment, external system 1120 includes an external device for use by the patient, for example, to initiate and/or time the delivery of the light therapy from implantable medical device 910 as directed by the physician or other caregiver. In another embodiment, external system 1120 includes a patient management system, such as the one discussed below with reference to
At 1610, a light emission duration is started. The light emission duration is a time interval during which a light is emitted to an ischemic region in a patient's body to relieve angina symptoms resulting from ischemia. In one embodiment, the light emission duration is started in response to the light emission command entered by a user, such as the patient, an attendant providing care to the patient, or a physician or other professional caregiver. In another embodiment, the light emission duration is started automatically according to a specified schedule, such as on a periodic basis using a programmed period. In one embodiment, the period is programmable between 1 minute and 72 hours.
At 1620, the light emission duration is timed. In one embodiment, the light emission duration is programmable between 10 seconds and 60 minutes.
At 1630, a light source is powered. The light source is incorporated into an intravascular stent placed in or near the ischemic region in the patient's body. Examples of the light source include one or more LEDs, such as one or more LEDs in die form or one or more PLEDs. In one embodiment, the light source is powered by a power source that is also incorporated into the intravascular stent. In one embodiment, the power source receives a power transmission signal from a device external to the body via a telemetry link capable of power transmission, such as an inductive or ultrasonic couple.
At 1640, a light is emitted from the light source during the light emission duration. The light has characteristics suitable for reliving angina symptoms. In one embodiment, the light has a wavelength between 600 nanometers and 1,000 nanometers, with approximately 800 nanometers being a specific example.
In one embodiment, the light emission duration is started at 1610 and timed at 1620 using circuitry incorporated into the intravascular stent. In another embodiment, the light emission duration is started at 1610 using an external system communicatively coupled to circuitry incorporated into the intravascular stent, and timed at 1620 using circuitry incorporated into the intravascular stent. In another embodiment, the light emission duration is started at 1610 and timed at 1620 using the external system communicatively coupled to the circuitry incorporated into the intravascular stent.
It is to be understood that the above detailed description is intended to be illustrative, and not restrictive. Other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
