DISCRIMINATION BETWEEN EFFECTIVE AND INEFFECTIVE ATRIAL PACING PULSES IN AN ACTIVE IMPLANTABLE MEDICAL DEVICE OF THE PACEMAKER TYPE
An active implantable medical device of the cardiac pacing, resynchronization, defibrillation and/or cardio version type able to discriminate between effective and ineffective atrial pacing pulses. This device delivers atrial pacing pulses, collects an endocardial atrial signal, and senses atrial capture. It is able to recognize the presence of an evoked wave consecutive to the delivery of the pacing pulse, by an analysis of the variations of a second derivative of collected signal. A function is calculated based on integrating, over the duration of a window (F) of post-atrial pacing (StimA) atrial sensing, the absolute value of the second derivative (S″) of collected signal (S). The discrimination between effective pacing pulses and ineffective pacing pulses is performed in response to the comparison of a characteristic parameter of said function with a predetermined criterion.
1 . An active implantable medical device for pacing, resynchronization, defibrillation and/or cardioversion, comprising:
means for delivering atrial pacing pulses,
means for collecting an atrial endocardial signal, and
means for sensing atrial capture, able to recognize the presence of an evoked wave consecutive to a delivered pacing pulse, said sensing means comprising
means for analyzing the variations of a second derivative of the collected signal,
means for calculating a function integrating, over a duration of a window of post-atrial pacing atrial sensing, an absolute value of said second derivative, and
means for discriminating between effective pacing pulses and ineffective pacing pulses, in response to a comparison of a parameter characteristic of said function to a predetermined criterion.
2 . The device of claim 1 , wherein said parameter characteristic is a final value reached by said function at the end of the post-atrial pacing atrial sensing window.
3 . The device of claim 1 , wherein said parameter characteristic is a duration required for said function to reach a predetermined percentage of the final value reached by said function at the end of the post-atrial pacing atrial sensing window.
4 . The device of claim 1 , wherein said parameter characteristic is a slope of said function at the beginning of the post-atrial pacing atrial sensing window.
5 . The device of claim 1 , comprising further means for searching the capture threshold by a dichotomy.
6 . The device of claim 5 wherein said dichotomy threshold capture searching means further comprises
means for selecting a first energy level;
means for delivering a stimulation pulse at said first energy level;
first means responsive to said first energy level stimulation pulse being effective in the absence of a spontaneous beat for selecting a lower energy for a subsequent stimulation pulse;
second means responsive to said first energy level stimulation pulse being ineffective for selecting a higher energy level for a subsequent stimulation pulse;
means for continuing to adjust the energy level using said first or second responsive means until a second successive decrease in stimulation energy results in an ineffective capture.