Cardiac stimulating apparatus and method for heart failure therapy
First Claim
1. A method of operating an implantable cardiac stimulator implanted in a patient suffering from congestive heart failure, said cardiac stimulator being of the type having means for sensing atrial activity, means for sensing ventricular activity, means for sensing cardiac function of the heart, means for stimulating at least one ventricular chamber, and microprogrammable controller means coupled to said means for sensing said atrial activity, said means for sensing ventricular activity and said means for sensing cardiac function, said microprogrammable controller means controlling said means for stimulating said at least one ventricular chamber so as to issue ventricular stimulating pulses at computed AV delay intervals following the sensing of an atrial event, comprising the steps of:
- (a) computing the electromechanical interval (EMI) of the patient'"'"'s heart using information derived from said cardiac function sensing means, said atrial sensing means and said ventricular sensing means;
(b) computing the atrial cycle length (ACL) of the patient'"'"'s heart using information derived from said atrial sensing means;
(c) changing the AV delay parameter of said pacemaker by a known increment from a previous value when it is determined that EMI is less than ACL;
(d) using said cardiac function sensing means to determine whether each of the incremental changes in the AV delay parameter enhanced the cardiac function of the patient'"'"'s heart measured on a previous cycle;
(e) repeating steps (a)-(d) until it is determined in step (d) that cardiac function degraded; and
(f) adjusting the AV interval by a pre-programmed small time value.
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Accused Products
Abstract
A cardiac rhythm management device includes a dual-chamber pacemaker especially designed for treating congestive heart failure and a defibrillator as a back-up measure. The device incorporates a programmed microcontroller which is operative to adjust the AV delay of the pacemaker to a minimum or maximum length consistent with optimal cardiac function. The cardiac stimulator includes apparatus for sensing cardiac function from cycle-to-cycle and determining whether incremental changes made to the AV delay interval enhances or worsens the measured cardiac function. On each iterative cycle, the AV delay interval is changed, either incremented or decremented, until a cross-over point is reached in which it is noted that the cardiac function ceases to improve and this is followed with a further incremental adjustment in an opposite direction to compensate for any overshoot. By providing a cardiac defibrillator in combination with the pacing device with closed-loop control of the AV interval, incidences of sudden death due to lethal arrhythmias is reduced.
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Citations
13 Claims
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1. A method of operating an implantable cardiac stimulator implanted in a patient suffering from congestive heart failure, said cardiac stimulator being of the type having means for sensing atrial activity, means for sensing ventricular activity, means for sensing cardiac function of the heart, means for stimulating at least one ventricular chamber, and microprogrammable controller means coupled to said means for sensing said atrial activity, said means for sensing ventricular activity and said means for sensing cardiac function, said microprogrammable controller means controlling said means for stimulating said at least one ventricular chamber so as to issue ventricular stimulating pulses at computed AV delay intervals following the sensing of an atrial event, comprising the steps of:
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(a) computing the electromechanical interval (EMI) of the patient'"'"'s heart using information derived from said cardiac function sensing means, said atrial sensing means and said ventricular sensing means; (b) computing the atrial cycle length (ACL) of the patient'"'"'s heart using information derived from said atrial sensing means; (c) changing the AV delay parameter of said pacemaker by a known increment from a previous value when it is determined that EMI is less than ACL; (d) using said cardiac function sensing means to determine whether each of the incremental changes in the AV delay parameter enhanced the cardiac function of the patient'"'"'s heart measured on a previous cycle; (e) repeating steps (a)-(d) until it is determined in step (d) that cardiac function degraded; and (f) adjusting the AV interval by a pre-programmed small time value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A totally implantable cardiac pacemaker for treating congestive heart failure comprising, in combination:
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(a) means for periodically measuring the EMI of the patient'"'"'s heart; (b) means for periodically measuring the ACL of the patient'"'"'s heart; (c) means for producing a cardiac tissue stimulating pulse upon the extraction of a computed AV interval following the occurrence of an atrial event; (d) means coupled to said EMI measuring means and said ACL measuring means for periodically comparing the magnitude of said EMI and said ACL on repetitive cycles and for changing an existing AV interval by a predetermined time increment when EMI is less than ACL; (e) means for measuring a predetermined cardiac function of the heart during each of said repetitive cycles and comparing said cardiac function to that existing prior to the time that said AV interval had been changed; and (f) means for decreasing said AV interval by a predetermined amount only when the comparison of the two cardiac functions on successive cycles shows a decrease in said cardiac function in the latter of said successive cycles. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification