Source: http://www.google.com/patents/US8118751?dq=7800613
Timestamp: 2014-09-23 21:40:16
Document Index: 261869987

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US8118751 - Devices and methods for accelerometer-based characterization of cardiac ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsSystems according to the invention employ an acceleration sensor to characterize displacement and vibrational LV motion, and uses this motion data to characterize the different phases of the LV cycle for analyzing LV function. Systems may identify a target pacing region or regions in the LV or RV using...http://www.google.com/patents/US8118751?utm_source=gb-gplus-sharePatent US8118751 - Devices and methods for accelerometer-based characterization of cardiac function and identification of LV target pacing zonesAdvanced Patent SearchPublication numberUS8118751 B2Publication typeGrantApplication numberUS 12/396,420Publication dateFeb 21, 2012Filing dateMar 2, 2009Priority dateFeb 7, 2005Also published asUS20060178586, US20060178589, US20090306736, US20100049063, WO2006086435A2, WO2006086435A3Publication number12396420, 396420, US 8118751 B2, US 8118751B2, US-B2-8118751, US8118751 B2, US8118751B2InventorsJohn D. Dobak, IIIOriginal AssigneeCardiosync, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (38), Non-Patent Citations (3), Referenced by (1), Classifications (15) External Links: USPTO, USPTO Assignment, EspacenetDevices and methods for accelerometer-based characterization of cardiac function and identification of LV target pacing zonesUS 8118751 B2Abstract Systems according to the invention employ an acceleration sensor to characterize displacement and vibrational LV motion, and uses this motion data to characterize the different phases of the LV cycle for analyzing LV function. Systems may identify a target pacing region or regions in the LV or RV using the acceleration sensor by localizing regions of late onset of motion relative to the QRS, or isovolumic contraction, or mitral valve closure, or by pacing of target regions and measuring LV function in response to pacing. Systems further provide an implantable or non-implantable acceleration sensor device for measuring LV motion and characterizing LV function. An implantable myocardial acceleration sensing system (�IAD�) includes at least one acceleration sensor, a data acquisition and processing device, and an electromagnetic, e.g., RF, communication device. The IAD may be integrated into the pacing lead of a CRT device and can operate independently of the CRT IPG.
The invention claimed is: 1. A device for monitoring cardiac function, comprising:
REFERENCE TO CONTINUING APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 11/318,325, filed Dec. 23, 2005 now abandoned, entitled �Devices and Methods For Accelerometer-Based Characterization of Cardiac Function and Identification of LV Target Pacing Zones, which claims the benefit of U.S. Provisional Application No. 60/650,532, filed Feb. 7, 2005, U.S. Provisional Application No. 60/655,038, filed Feb. 22, 2005, U.S. Provisional Application No. 60/656,307, filed Feb. 25, 2005, U.S. Provisional Application No. 60/657,766, filed Mar. 1, 2005, U.S. Provisional Application No. 60/659,658, filed Mar. 8, 2005, U.S. Provisional Application No. 60/663,788, filed Mar. 21, 2005, U.S. Provisional Application No. 60/669,324, filed Apr. 7, 2005, U.S. Provisional Application No. 60/677,569, filed May 4, 2005 and U.S. Provisional Application No. 60/680,673, filed May 13, 2005. Each of the prior US Provisional Patent Applications is incorporated by reference in its entirety herein.
BACKGROUND The human heart delivers oxygenated blood to the organs of the body to sustain metabolism. The human heart has four chambers, two atria and two ventricles. The atria assist with filling of the ventricles, which pump blood to the body and through the lungs. The right ventricle (RV) pumps blood through the lungs to be oxygenated and the left ventricle (LV) pumps the oxygenated blood to the body.
A graph of the cardiac filling and pumping cycle and valvular events is shown in FIGS. 1 a and 1 b. The cardiac LV pumping cycle (LV cycle) is divided into two periods: diastole 52 and systole 54. Diastole 52 is the filling period and systole 54 is the ejection period. Five different phases of the LV cycle can be identified within the systolic and diastolic periods: isovolumic contraction 56, ejection 58, isovolumic relaxation 62, early diastolic filling (rapid filling) 64, and late diastolic filling (atrial contraction) 66. Mitral valve closure 68 (�MVC�) occurs during isovolumic contraction and aortic valve closure 72 (�AVC�) occurs during isovolumic relaxation. Also shown in the figures are the left ventricular pressure LV Press 74, a regular electrocardiogram ECG 76, the left ventricular end-diastolic volume LVEDV 78, the left ventricular end-systolic volume LVESV 82, a graph depicting heart sounds 84, the left atrial pressure LA Press 86, the aortic pressure 88, a-wave 92, c-wave 94, and v-wave 96.
Pacemaker therapy to treat heart failure is an established medical therapy. This therapy is employed to correct the dyssynchronous mechanical activity that occurs in heart failure by controlling the electrical activity of the heart. This form of pacing therapy is often referred to as cardiac resynchronization therapy or CRT. Dual chamber pacing (right atrium and right ventricle) to improve atrioventricular synchrony is a form of pacemaker therapy. Biventricular pacing is a newer approach that can improve cardiac function and mortality. Tachyarrhythmia and defibrillation therapy are also incorporated into the pacing therapy as heart failure patients often have problems with tachyarrhythmia. An experimental implantable pacing therapy for cardiomyopathy is cardiac contractility modulation (�CCM�) in which a voltage potential or current is applied to the myocardium during the tissue's refractory period. This current improves myocardial contractility.
In biventricular pacing or CRT, cardiac leads are placed in the right atrium (RA), the RV, and LV coronary veins via the coronary sinus. The leads have electrodes that can sense cardiac electrical activity and stimulate contraction in the myocardium. The leads are connected to a hermetically sealed, battery powered, programmable pulse generator and sensor/data storage device, termed here an �IPG� that is implanted subcutaneously.
SUMMARY OF THE INVENTION To the best of the inventor's knowledge none of the above disclosures proposes using acceleration sensors to characterize all components of LV motion, displacement and vibration, and to use this motion data to characterize the different phases of the LV cycle for analyzing LV function. These disclosures do not provide a means for separating out the displacement and vibrational components of LV motion, which occur at the same time, through different frequency sensing or filtering and analysis. Prior disclosures do not provide devices or methods for identifying the optimal myocardial pacing zone or region in the left or right ventricle for CRT, such as measuring the onset of motion relative to the onset of the QRS or isovolumic contraction or mitral valve closure. Prior disclosure do not provide a method for multiple catheter repositionings in the LV or coronary sinus or great cardiac vein to map the motion of the LV for identifying the optimal pacing region. Prior disclosures do not describe characterizing the response to pacing of a target region by measuring parameters indicative of r LV function (e.g., myocardial performance index or QRS onset to aortic valve closure). Prior disclosures also do not disclose measuring cardiac pathologies such as mitral regurgitation, which may be sensed as vibration motion at frequencies greater than about 150 Hz. Prior disclosures do not disclose a means for optimizing complete cardiomyopathy therapy, including drugs and devices, through the use of implantable acceleration devices. Prior disclosures do not provide a means for zeroing out gravity effects and tilt of the sensor. Prior disclosures do not define the use of capacitive acceleration sensors that integrate an inductive coil for wireless powering and data transmission.
Rather, prior disclosures typically describe a single acceleration sensor preferably disposed in the tip of an implantable pacing lead. For example, a single accelerometer is incorporated into the RV pacing lead to assess RV systolic activity and correlate the readings with RV dP/dt (�An implantable intracardiac accelerometer for monitoring myocardial contractility�, PACE 1996, 19:2066-2071). The sensor is designed to detect only signals related to isovolumic contraction, and not the motion related to displacement or valvular pathologies. In another disclosure, an accelerometer is incorporated into an LV pacing lead for optimization of CRT timing intervals (US Application 2004/0172079 A1). This prior disclosure proposes to sense LV myocardial acceleration during isovolumic contraction and use this information to optimize the atrioventricular delay and the interventricular delay pacing signals. There is no disclosure on the use of an acceleration sensor device to identify target pacing regions and characterize the LV functional response to pacing. There is no disclosure on a means for characterizing both the displacement and vibration motion occurring at different frequencies. Consequently, the disclosure does not provide a way to monitor information on phases of the LV cycle that characterize LV function such as, displacement related to ejection, filling, afterload, volume status, and preload, nor can the same characterize vibration related to mitral regurgitation. Additionally, no disclosure is provided for integrating the acceleration signal to yield LV displacement velocity and distance measurements, which may provide additional information on LV contractile function. Also, neither disclosure nor device design is provided that would allow characterization of myocardial strain and strain rate.
Embodiments of the invention provide an implantable or non-implantable acceleration sensor device for measuring LV motion and characterizing LV function. An implantable myocardial acceleration sensing system (�IAD�) includes at least one acceleration sensor, a data acquisition and processing device, and an electromagnetic, e.g., RF, communication device. The system may or may not have an internal battery. In one embodiment, an IAD is integrated into the pacing lead of a CRT device and can operate independently of the CRT IPG. In another embodiment, an IAD is used without a CRT to monitor heart failure. In this embodiment, at least one sensor is incorporated into an endovascular catheter that can be placed in the epicardial venous system of the LV.
In one illustrative system, the accelerometer sensors are micro-electromechanically (�MEM�s)-based to allow miniaturization, low-power consumption, and multiple-axis sensing. The sensor are conductively attached to the subcutaneously-implanted data acquisition and processing device, which is capable of RF telemetry communication and data transfer. The IAD monitors both vibrational and displacement LV motion during systole and diastole in at least the longitudinal axis. The IAD may also monitor LV acceleration in at least one location near the mitral annulus.
In another embodiment, the sensor is a radiofrequency (�RF�) MEMs accelerometer that incorporates coils that can inductively power or charge the sensor and transmit the data. Such an RF sensor provides long term, batteryless, wireless monitoring. Data from the wireless RF sensor may be acquired using an external antenna device that wirelessly couples to the sensor by directing electromagnetic energy of the appropriate frequency toward the sensor for inductive powering and/or data transmission. The antenna device is connected to a microprocessor-controlled display device that processes and stores the myocardial acceleration data for LV motion and therapy monitoring and optimization.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B show graphs depicting various parameters of the cardiac pumping and ECG cycle.
DETAILED DESCRIPTION Acceleration sensors are well-suited for measuring both vibration and displacement motions. They can be oriented along an appropriate axis to maximize the motion signal and to accurately measure the displacement. An acceleration sensor placed in or on the heart can measure vibrational or displacement components of heart motion, or both thereby allowing the characterization of pumping function and various pathologies.
RF sensor monitoring and data transfer could occur via an antenna device connected to a microprocessor which is worn by the patient or held near the sensor (e.g., over the chest). An appropriate antenna device would have a large enough antenna to inductively couple with the sensor. In one illustrative system, the antenna device may couple with the sensor at a distance of 5 to 15 cm and up to 15 feet. An exemplary antenna device is discussed in �RF telemetry system for an implantable bio-MEMs sensor�, Rainee Simons, et al., NASA Glen Technical Reports, June 2004, NASA TM-2004-212899. As discussed in this paper, an MMIC amplifier connected to the antenna can allow for a reduction in the size of the sensor coil and the reader antenna.
For trend monitoring (e.g., with an IAD), acceleration data is sampled at regular intervals during the day, termed the �interval period�, and this data is averaged. Peak amplitudes can be plotted as the ordinate with the monitored time interval (e.g., days, weeks, or months) as the abscissa (See FIG. 18). Data points may indicate the average amplitude of the peaks from the interval samples. Statistical analysis of these trends can identify changes from baseline function that may warrant an intervention.
Referring to FIGS. 25 and 33, which shows myocardial motion mapping, display output, and target pacing identification through a roving pace guidewire, changes or variables indicative of a favorable LV functional response may be sensed at the low, mid, and high frequency ranges. In the figure, �MVR� refers to mitral valve regurgitation, �IVC� refers to isovolumic contraction, and �IVR� refers to isovolumic relaxation. The top curve is ECG 556, curve 558 shows the velocity or LV displacement, obtained by integrating the acceleration signal, curve 562 shows LV function, and curve 562 shows the sounds of mitral valve regurgitation.
Referring in more detail to FIG. 29, a chart is shown which may be used to identify regions of late deformation and for assessing various other variables related to performance. Curve 668 shows the ECG signal, curve 672 shows the acceleration signal, where the left-most point is the zero point established by the QRS, �EP� refers to the ejection phase, �E� refers to early diastolic filling, �A� refers to atrial contraction filling, time interval �A� measures the start of IVC to the end of IVR, and time interval �B� measures the time interval of the EP. MPI=(A−B)/B. Curve 674 shows the acceleration signal from region #1, showing in particular the IVC time interval 676 and the peak IVC signal 678, as well as the delayed mechanical shortening 682 in the target pacing region. Referring to FIG. 30, an alternative mapping strategy may also be employed in which a simplified catheter with only a 1, 1 pair sensor, i.e., perpendicular to each other, or 3 sensors, each perpendicular to each other, uniaxial, biaxial, or triaxial, is positioned in various LV and LV locations, e.g., septal to lateral in the coronary sinus and great cardiac vein). One sensor or sensor pair detects both the onset of systole or diastole, e.g., isovolumic contraction or relaxation; or aortic or mitral valve closure, and regional motion, or one of two sensors or one of two sensor pairs may be utilized to detect the same onset of systole or diastole and the other sensor or sensor pair detects the regional motion. Alternatively, 3 axes of a dual axis pair may be used for displacement sensing and the 4th axis may be used for vibration sensing. Alternatively, 3 axes of a 3-sensor device may be used for sensing displacement motion, and the other 3 axes may be used for sensing vibrational motion. No electrodes, one electrode, or two electrodes may be employed.
A venous sheath 838 is used to gain access to the right atrium (�RA�) via the subclavian or femoral vein. This sheath may include an optional mid- to high-frequency acceleration sensor 842. The sheath may have appropriate bends to facilitate entry into the coronary sinus.
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