Cardiac pacemaker with hystersis behavior

Abstract

A pacemaker having a hysteresis feature which permits intrinsic heart activity, controlled by the sinus node to resume optimally after pacing. The pacemaker has a programmable lower rate and upper rate, a programmable lower hysteresis rate (LRH) corresponding to a lower rate hysteresis interval (LRHI), and a programmable rate (IR) intermediate an upper pacing rate (UR) and a lower pacing rate (LR). A microprocessor measures the average rate of change MAVG in the intervals between consecutive ventricular depolarizations, and compares the last intrinsic escape interval RRN to the lower rate hysteresis interval (LRHI).If the last intrinsic escape interval RRN is longer than the lower rate hysteresis interval (LRHI), and if the value of MAVG is greater than a first preselected value SL1 but less than a second preselected value SL2, the pacemaker stimulates at the lower rate hysteresis (LRH) and thereafter gradually increases the pacing rate up to the intermediate rate (IR). A time counter maintains a continuous pacing at the intermediate rate (IR) for a predefined period of time, and the pacing rate is gradually decreased toward the lower pacing rate (LR).

Description

BACKGROUND OF THE INVENTIONThe present invention relates to cardiac pacemakers, and more specifically to a pacemaker having a selectable hysteresis feature which compensates for sinus node malfunction.It is well known that natural heart activity, including the depolarization of the sinus node provides optimum hemodynamic performance. Atrial or ventricular stimulations induced by such devices as cardiac pacemakers, generally delay or inhibit natural heart activity by preventing the depolarization of the sinus node.The hysteresis feature was developed to address this concern, by allowing the pacemaker to follow the sensed sinus node depolarization to a certain predetermined rate below the programmed lower rate of the pacemaker. As such, the escape interval in conventional demand pacemakers equipped with hysteresis feature, is longer than the lower rate interval, for enabling the patient's intrinsic rhythm to control the heart as long as the intrinsic rate is maintained above a predete...

AI Technical Summary

Problems solved by technology

Atrial or ventricular stimulations induced by such devices as cardiac pacemakers, generally delay or inhibit natural heart activity by preventing the depolarization of the sinus node.

However, in selected patients, these conventional pacemakers do not generally allow the natural heart activity to resume normally after pacing.

While the above cited patents and other publications and studies relating to the hysteresis feature have attempted with varying degrees of success to allow the patient's intrinsic rhythm to control, none was completely successful in causing the natural heart activity to resume optimally after pacing.

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