Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-07-14
2003-02-18
Layno, Carl (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C600S536000, C607S008000
Reexamination Certificate
active
06522914
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to sensing and controlling cardiac activities in implantable devices including, but not limited to, bradycardia pacemakers and cardioverter defibrillators. More particularly, the invention concerns such a device in which an intracardiac impedance-derived parameter, Half Cycle Activity (HCA) is used as a key variable.
BACKGROUND OF THE INVENTION
It is a well-recognized challenge to monitor accurately physical demands on cardiac support imposed by different levels of work or exercise a patient engages in (Barold et al., Clin Cardiol (1997), Vol 20 (8): 726-9; Alt, Am J Cardiol (1999), Vol 83(5B): 17D-23D). And yet, it is essential for a cardiac pacemaker to operate at a pacing rate that correlates with the workload presented. It is equally essential for a cardioverter defibrillator to determine hemodynamic status of a patient before diagnosing a life-threatening arrhythmia and exerting ventricular anti-tachy therapy (Johnston et al., Eur Heart J (1998), Vol. 19 (12):1879-88). A variety of physiologic or non-physiologic sensors have been designed during the last two decades to produce a signal directly related to the metabolic demand, including blood pH (U.S. Pat. No. 4,009,721), QT interval (U.S. Pat. No. 4,228,803), blood O
2
saturation (U.S. Pat. No. 4,399,820), blood temperature (U.S. Pat. No. 4,543,954), pressure sensor (U.S. Pat. Nos. 4,899,752 and 5,105,819), piezoelectric crystal (U.S. Pat. Nos. 4,140,132 and 4,428,378), accelerometer (U.S. Pat. Nos. 5,235,237 and 5,383,473), micro-accelerometer (U.S. Pat. Nos. 5,423,883, 5,480,412, Rickards et al., The Multicenter PEA Study Group—PACE (1996) 19:12 Pt1, 2066-2071), thoracic and intracardiac impedance (U.S. Pat. Nos. 3,593,718, 4,291,699, 4,773,401, 5,085,583, 5,235,976, 5,562,711 and 5,782,884) etc. These sensors are less than optimal and have led to little commercial success for various reasons, including difficulty to implement due to the need for specific hardware, lack of correlation between the signal and actual workload, lack of hemodynamic feedback information, slow response, and lack of robustness, i.e., high sensitivity to noise or artifacts inherent to the signal.
SUMMARY OF THE INVENTION
To resolve the above problems, the present invention is directed to an improved method and apparatus for monitoring hemodynamic activities in implantable cardiac devices. In particular, the present invention relates to cardiac pacemakers, cardioverter defibrillators and like devices that use a physiologic sensing parameter, Half Cycle Activity (HCA) to monitor and adjust cardiac activities.
In accordance with one aspect of the invention, the impedance-derived parameter HCA correlates closely with the workload and at the same time provides hemodynamic feedback information. Thus, it allows a pacemaker system to implement accurately an increase in hemodynamically driven pacing rate, as well as to limit an inappropriate decrease of driven pacing rate advised by another sensor such as an accelerometer. On the other hand, it determines the maximum pacing rate for the pacemaker, thus preventing hemodynamic compromise from occurring.
In accordance with another aspect of the invention, this intracardiac impedance-derived parameter HCA is resistant to noise or artifacts. Unlike other sensing parameters, HCA measurement is based on the whole impedance waveform; therefore, it is robust to local artifacts. Additionally, HCA is based on a baseline-corrected impedance signal; thus, it is much more resistant to baseline shifts than other impedance-derived parameters.
In accordance with yet another aspect of the present invention, the implementation of such parameter, in particular HCA, uses a single bipolar ventricular pacing and sensing lead in a pacemaker or defibrillator. Such a ventricular lead is connected to a sensing module to gather sensed physiological events. Specifically, an impedance reading module connected to the ventricular lead reads impedance signals, which is directed to the HCA microprocessor, where HCA computation takes place in real time. The result of HCA values is then fed back into a pacing controller module, which through a pacing module completes the adjustment to the cardiac stimulating events such as the pacing rates.
The present invention with all aspects of an impedance-derived parameter such as HCA, therefore, brings significant improvements in cardiac activity management devices.
REFERENCES:
patent: 4291699 (1981-09-01), Geddes et al.
patent: 4562843 (1986-01-01), Djordjevich et al.
patent: 4773401 (1988-09-01), Citak et al.
patent: 5085583 (1992-02-01), Amos et al.
patent: 5235237 (1993-08-01), Leonhardt
patent: 5235976 (1993-08-01), Spinelli
patent: 5300093 (1994-04-01), Koestner et al.
patent: 5383473 (1995-01-01), Moberg
patent: 5423883 (1995-06-01), Helland
patent: 5480412 (1996-01-01), Mouchawar et al.
patent: 5562711 (1996-10-01), Yerich et al.
patent: 5685316 (1997-11-01), Schookin et al.
patent: 5782884 (1998-07-01), Stotts et al.
patent: 6049735 (2000-04-01), Hartley et al.
patent: 0 555 988 (1993-08-01), None
patent: WO 98/14240 (1998-04-01), None
Schaldach, Max, “Automatic Adjustment of Pacing Parameters Based on Intracardiac Impedance Measurements”, PACE, vol. 13, Dec. 1990, Part II, pp. 1702-1710.
Salo, Rodney W., “Measurement of Ventricular Volume by Intracardiac Impedance: Theoretical and Empirical Approaches”, IEEE Transactions on Biomedical Engineering, vol. BM#-33, #2, 2/86, pp. 189-195.
Salo, Rodney W. et al., “Continuous Ventricular Volume Assessment for Diagnosis and Pacemaker Control” PACE, vol. 7, Nov.-Dec. 1984, Part II, pp. 1267-1272.
Alt, Eckhard, “What Is the Ideal Rate-Adaptive Sensor for Patients with Implantable Cardioverter Lessons from Cardiac Pacing,” Am. J. Cardiol. 1999; 83:17D-23D.
Barold, Serge, et al., “Contemporary Issues in Rate-Adaptive Pacing”, Clin. Cardiol. 20, 726-729 (1997).
Johnston, P.W., et al., “The transthoracic impedance cardiogram is a potential haemodynamic sensor for an Automated external defibrillator”, European Heart Journal (1998) 19, 1879-1888.
Rickards, Anthony, et al., “An Implantable Intracardiac Accelerometer for Monitoring Myocardial Contractility”, PACE, vol. 19, Dec. 1996, Part I, pp. 2066-207166.
Huvelle Etienne
Sanchez Francisca Cuesta
Cardiac Pacemakers Inc.
Layno Carl
LandOfFree
Method and apparatuses for monitoring hemodynamic activities... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatuses for monitoring hemodynamic activities..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatuses for monitoring hemodynamic activities... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3172204