Patent Application
20140309538
This disclosure relates generally to apparatus and methods for detection of phrenic nerve stimulation.
Phrenic Nerve Stimulation (PNS) occurs in about 10% of all cardiac resynchronization therapy (CRT) patients. It is estimated that nearly 3% of the patients have to be re-operated to correct PNS. To decrease the probability of PNS, it is necessary to bypass pacing vectors that cause PNS. For example, some medical personnel or medical device manufacturers have suggested using multiple pacing configurations to bypass the pacing vector that causes PNS. For example, a pacing lead may provide a multiple quantity of pacing options to the medical personnel (e.g., physician) with the primary goal of picking the best suited pacing option for avoiding phrenic nerve stimulation. Although software-driven workflows have graphically eased the way to test all the offered vector options, there is still no automatic test to check for PNS in all the offered vector options. Thus, a prevalent current practice is for the medical personnel (e.g., physician) to hold his or her hand over the patient's chest and confirm any diaphragm movement as a way of detecting PNS.
Disclosed is an apparatus and method for detecting phrenic nerve stimulation. According to one aspect, a method for detecting phrenic nerve stimulation (PNS) including computing a power spectral density (PSD) of spatial data of a sensor; determining a first spectral magnitude and a second spectral magnitude from the power spectral density (PSD); computing a ratio of the first spectral magnitude to the second spectral magnitude; and comparing the ratio to a threshold, wherein if the ratio is equal or greater than the threshold, determining that phrenic nerve stimulation (PNS) is present and wherein if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a device for detecting phrenic nerve stimulation (PNS) comprising a processor and a memory, the memory containing program code executable by the processor for performing the following: computing a power spectral density (PSD) of spatial data of a sensor; determining a first spectral magnitude and a second spectral magnitude from the power spectral density (PSD); computing a ratio of the first spectral magnitude to the second spectral magnitude; and comparing the ratio to a threshold, wherein if the ratio is equal or greater than the threshold, determining that phrenic nerve stimulation (PNS) is present and wherein if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a method for detecting phrenic nerve stimulation (PNS) including computing a power spectral density (PSD) of spatial data of a sensor, wherein the sensor is an external sensor placed on a patient's torso area; determining a diaphragmatic spectral magnitude and a respiratory motion spectral magnitude from the power spectral density (PSD); and computing a ratio of the diaphragmatic spectral magnitude to the respiratory motion spectral magnitude, wherein if the ratio is equal or greater than a threshold, determining that phrenic nerve stimulation (PNS) is present, and if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a device for detecting phrenic nerve stimulation (PNS) comprising a processor and a memory, the memory containing program code executable by the processor for performing the following: computing a power spectral density (PSD) of spatial data of a sensor, wherein the sensor is an external sensor placed on a patient's torso area; determining a diaphragmatic spectral magnitude and a respiratory motion spectral magnitude from the power spectral density (PSD); and computing a ratio of the diaphragmatic spectral magnitude to the respiratory motion spectral magnitude, wherein if the ratio is equal or greater than a threshold, determining that phrenic nerve stimulation (PNS) is present, and if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a method for detecting phrenic nerve stimulation (PNS) including computing an oscillation amplitude of spatial data of a sensor; computing a baseline wander amplitude of the spatial data of the sensor; computing a ratio of the oscillation amplitude to the baseline wander amplitude; and comparing the ratio to a threshold, wherein if the ratio is equal or greater than a threshold, determining that phrenic nerve stimulation (PNS) is present, and wherein if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a device for detecting phrenic nerve stimulation (PNS) comprising a processor and a memory, the memory containing program code executable by the processor for performing the following: computing an oscillation amplitude of spatial data of a sensor; computing a baseline wander amplitude of the spatial data of the sensor; computing a ratio of the oscillation amplitude to the baseline wander amplitude; and comparing the ratio to a threshold, wherein if the ratio is equal or greater than the threshold, determining that phrenic nerve stimulation (PNS) is present, and wherein if the ratio is less than the threshold, determining that no PNS or minimal PNS is present.
According to one aspect, a method for detecting phrenic nerve stimulation (PNS) including obtaining a first respiratory spectral magnitude with no phrenic nerve stimulation (PNS) or minimal PNS is present; defining a threshold based on the first respiratory spectral magnitude; determining a second respiratory spectral magnitude from a power spectral density of spatial data of a sensor; and determining that a phrenic nerve stimulation (PNS) is present if the second respiratory spectral magnitude is less than the threshold or determining that no PNS or minimal PNS is present if the second respiratory spectral magnitude is equal or greater than the threshold.
According to one aspect, a device for detecting phrenic nerve stimulation (PNS) comprising a processor and a memory, the memory containing program code executable by the processor for performing the following: obtaining a first respiratory spectral magnitude with no phrenic nerve stimulation (PNS) or minimal PNS is present; defining a threshold based on the first respiratory spectral magnitude; determining a second respiratory spectral magnitude from a power spectral density of spatial data of a sensor; and determining that a phrenic nerve stimulation (PNS) is present if the second respiratory spectral magnitude is less than the threshold or determining that no PNS or minimal PNS is present if the second respiratory spectral magnitude is equal or greater than the threshold.
Advantages of the present disclosure may include decreasing or minimizing involvement of medical personnel in the detection of phrenic nerve stimulation (PNS) by providing an automated PNS detection procedure, eliminating guess work and reducing human error.
It is understood that other aspects will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described various aspects by way of illustration. The drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.
The detailed description set forth below in connection with the appended drawings is intended as a description of various aspects of the present disclosure and is not intended to represent the only aspects in which the present disclosure may be practiced. Each aspect described in this disclosure is provided merely as an example or illustration of the present disclosure, and should not necessarily be construed as preferred or advantageous over other aspects. The detailed description includes specific details for the purpose of providing a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present disclosure. Acronyms and other descriptive terminology may be used merely for convenience and clarity and are not intended to limit the scope of the present disclosure.
While for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more aspects, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more aspects.
Three dimensional (3D) position and orientation information of multiple tools can be collected in real time. Using the X, Y and Z coordinates of a sensor, a plot of displacement over time may be drawn for any given time interval.
The oscillation characteristic of the X, Y and Z coordinate plots shown in
In one example, real time tracking of the sensor within a coronary sinus branch during pacing allows computing the cardiac motion spectral magnitude to respiratory motion spectral magnitude ratio just by using a few cardiac cycles. Selecting the right coordinate axis that captures the major component of respiratory motion may help compute the ratio more accurately. Since more than one power spectral density (PSD) may be required for comparison, multiple pacing configurations may be advantageous to determine the lower cardiac motion spectral magnitude to respiratory motion spectral magnitude ratio. In one example, the lowest ratio may be deemed as normal pacing with no phrenic nerve stimulation (PNS). In the example of a single vector detection, a non-PNS graph may be computed by using an right ventricle (RV) pacing configuration as the baseline, that is, as having no phrenic nerve stimulation (PNS).
For example, once a pacing lead is in place within a patient and the condition is ready for pacing vector selection, the programmer paces through all pacing vectors sequentially with a selected pacing amplitude (e.g., a 10V pacing amplitude). For every single vector, the sensor system collects the 3D coordinates (i.e., X, Y and Z coordinates) of the sensor that is placed within the patient (e.g., in a patient's heart vessel). In one example, the sensor is associated with an enabled guidewire, an inner catheter or an outer catheter, any of which may be used during a cardiac resynchronization therapy (CRT) implant. Using the cardiac motion spectral magnitude to respiratory motion spectral magnitude ratio, the sensor system detects event of PNS and reports back to the programmer system via communication channel coupled between the two systems. In one example, the programmer system changes the pacing vector and applies a pulse (e.g., 10V pulse) to the new vector. This process is repeated for all the pacing vectors. At the end of the test, the programmer system generates a list of vectors that are marked with ‘PNS Detected’. In one example, the programmer system marks each of the pacing vectors with which PNS is detected. The vectors marked with ‘PNS Detected” are the pacing vectors with which PNS is detected.
In one example the process of automatic PNS detection may be incorporated with automatic capture threshold algorithm used on the implantable device programmer system. In one example, PNS may be detected by the stand-alone sensor system without communication with the programmer system based on the inputs from various sensors including a Patient Reference Sensor (PNS).
In one example, the sensor is embedded in a chest cavity. In another example, the sensor is embedded within a heart tissue. In one example, the sensor is embedded within a blood vessel. One example of the blood vessel is a coronary sinus branch. In yet another example, the sensor may be placed externally on a patient, such as, on a patient's torso area which may be on the chest area. In another example, the sensor is placed on the patient's back. One skilled in the art would understand that the location of the initial placement of the sensor may vary according to various factors, such as but not limited to, medical personnel's choice, patient's medical condition, the type or sensor used, etc., without affecting the scope and spirit of the present disclosure. Additionally, one skilled in the art would understand that the examples of the sensor's initial location disclosed herein are not exclusive.
In one example, the sensor is one of the following: an electromagnetic sensor, a ultrasonic sensor, an acoustic sensor, an impedance-based sensor, etc. In one example, the sensor is a set of multiple sensors of one of the following type of sensors: electromagnetic sensors, ultrasonic sensors or acoustic sensors impedance-based sensor. In one example, the multiple sensor set includes more than one type of sensors in its set. In one example, one or more sensors of the multiple sensor set is placed internally in the patient while another one or more sensors the multiple sensor set is placed externally on the patient. For example, a sensor may be placed within a branch of the coronary sinus, a sensor may be placed on the torso area, a sensor may be placed on the patient's back area, or combination thereof may be used.
Other types of sensors or combination of two or more of the types of sensors disclosed herein may be used. In one example, for the sensor placed internally in a patient, the sensor is associated with one of the following: a guidewire, a catheter, a lead, a stylet, etc.
In block 720, determine a first spectral magnitude and a second spectral magnitude from the power spectral density (PSD). In one example, the first spectral magnitude is a cardiac motion spectral magnitude, and the second spectral magnitude is a respiratory motion spectral magnitude. In another example, both the first and second spectral magnitude relate to a cardiac signal. In yet another example, both the first and second spectral magnitude relate to a respiratory signal. In one example, the cardiac motion spectral magnitude occurs at a higher frequency than the respiratory motion spectral magnitude. For example, the cardiac motion spectral magnitude may occur at a frequency between 1.5 to 3 Hz. And, for example, the respiratory motion spectral magnitude may occur at a frequency between 0 to 0.5 Hz.
In block 730, compute a ratio of the first spectral magnitude to the second spectral magnitude. Following block 730, in block 740, compare the ratio to a threshold. In one example, if the ratio is equal or greater than the threshold, determine that phrenic nerve stimulation (PNS) is present. And, if the ratio is less than the threshold, determine that no PNS or minimal PNS is present. In one example, the value of the threshold is derived from a right ventricle (RV) pacing configuration. In block 750, identify the PNS with a pacing vector. In one example, the pacing vector is a combination of a cathode and an anode configuration. In block 760, mark the pacing vector with a marker. In one example, the pacing vector is executed by a programmer system. In one example, the sensor is part of a sensor system, and a communication channel couples the sensor system with the programmer system so the two systems can communicate with each other. In one example, the programmer system marks the pacing vector with a marker to indicate that PNS was detected with that pacing vector.
In one aspect, the steps illustrated in
The various ways of computing PSD as described with the example of
In block 820, determine a diaphragmatic spectral magnitude and a respiratory motion spectral magnitude from the power spectral density (PSD). In block 830, compute a ratio of the diaphragmatic spectral magnitude to the respiratory motion spectral magnitude. In one example, if the ratio is equal or greater than a threshold, determine that phrenic nerve stimulation (PNS) is present. And, if the ratio is less than the threshold, determine that no PNS or minimal PNS is present. In one example, the value of the threshold is derived from a right ventricle (RV) pacing configuration. In block 840, identify the PNS with a pacing vector. In block 850, mark the pacing vector with a marker. In one example, the sensor is part of a sensor system which is coupled to a programmer system by a communication channel. In one example, the programmer system marks the pacing vector with a marker to indicate that that pacing vector is associated with a PNS.
In one example, one or more sensors of the multiple sensor set is placed internally in the patient while another one or more sensors the multiple sensor set is placed externally on the patient. For example, a sensor may be placed within a branch of the coronary sinus, a sensor may be placed on the torso area, a sensor may be placed on the patient's back area, or combination thereof may be used. In one example, for the sensor placed internally in a patient, the sensor is associated with one of the following: a guidewire, a catheter, a lead, a stylet, etc.
In one aspect, phrenic nerve stimulation (PNS) causes the diaphragm to contract and therefore prevent normal breathing, thereby limiting respiratory motion and concomitantly decreasing the respiratory spectral magnitude. The change in cardiac spectral magnitude may be secondary to this breathing effect. The contraction of the diaphragm causes inspiration, which reduces thoracic pressure, and thus, may reduce the resistance to cardiac motion.
In block 1020, define a threshold based on the first respiratory spectral magnitude. The threshold is used to indicate no phrenic nerve stimulation (no PNS). In block 1030, determine a second respiratory spectral magnitude from a power spectral density of spatial data of a sensor. In one example, the first and second respiratory spectral magnitudes are centered at a same frequency.
In one example, the spatial data includes one or more of the following: position data of the sensor over time or orientation data of the sensor over time. In one example, the sensor is one of the following: an electromagnetic sensor, a ultrasonic sensor, an acoustic sensor or an impedance-based sensor. In one example, the sensor is placed internally in a patient, for example, in a chest cavity, a heart tissue, a blood vessel, or a coronary sinus branch. In another example, the sensor is placed externally on a patient's torso area. The sensor may be a set of multiple sensors.
In one example, the pacing configurations for the first respiratory spectral magnitude and the second respiratory spectral magnitude are different. In one example, the power spectral density is based on a left ventricle (LV) pacing configuration. In one example the power spectral density (PSD) is computed by one of the following: taking a Fourier transform of the spatial data and/or taking the magnitude squared of the Fourier transform, using parametric spectral estimation of the spatial data; using non-parametric spectral estimation of the spatial data; taking a wavelet transform of the spatial data; taking a periodogram of the spatial data; or taking a periodogram of a moving average of the spatial data.
In block 1040, compare the second respiratory spectral magnitude and the threshold. In block 1050, determine that a phrenic nerve stimulation (PNS) is present if the second respiratory spectral magnitude is less than the threshold or determine that no PNS or minimal PNS is present if the second respiratory spectral magnitude is equal or greater than the threshold. In block 1060, identify the phrenic nerve stimulation (PNS) with a pacing vector and mark the pacing vector with a marker. In one example, repeat the steps of
While for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more aspects, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more aspects.
The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the spirit or scope of the disclosure.
