Patent ID: 7908002

Claim:
An implantable pacemaker comprising: a pulse generator adapted to interact with at least one ventricle of a heart to deliver pacing pulses to that ventricle; a cardiac signal detector adapted to interact with the heart to detect cardiac signals originating from an atrium of the heart; an arrhythmia detector connected to the cardiac signal detector that analyzes said cardiac signals to detect an occurrence of atrial arrhythmia; an impedance measuring unit adapted to interact with said atrium to measure an atrial impedance therein; and a controller connected to said pulse generator, said arrhythmia detector and said impedance measuring unit, said controller being configured to control said pulse generator to cause said pulse generator to deliver said pacing pulses to the ventricle in a P-wave synchronous mode as long as no atrial arrhythmia is detected by said arrhythmia detector, and to switch control of said pulse generator to a non-P-wave synchronous mode if atrial arrhythmia is detected by said arrhythmia detector, and to determine an atrial distention of said atrium from the atrial impedance measured by said impedance measuring unit and, in said non-P-wave synchronous mode, to control said pulse generator to increase a delivery rate of said pacing pulses to an increased delivery rate that said controller, by continuing to evaluate said atrial impedance measured by said impedance measuring unit, is determined by said controller to decrease said atrial distention during said atrial arrhythmia.