Timing Cycles in Dual-Chamber Adaptive Rate Pacemakers and the Consequences for Programming

Abstract

With the development of new and more sophisticated pacing modes, understanding of pacemaker rhythms can be difficult and time consuming. A profound knowledge of the nomenclature and timing of dual chamber adaptive rate (DDDR) pacing is mandatory to program the parameters and special functions, in order to fine tune the pacing therapy for each individual patient. A DDDR pacemaker can control the cardiac cycle by processing the input of three sources, i.e. the atrium, the ventricle and a sensor circuit. Each of these three inputs impacts every subsequent cardiac cycle, as determined by the programmed timing intervals. Timing intervals are distinct periods that occur during the cardiac cycle and between subsequent cardiac cycles. Pacemaker timing intervals can be compared to the alarms of a clock. At the appropriate ‘time’, the pacemaker delivers a pacing pulse to either the atrium or ventricle, much the same way an alarm rings in a clock at a set time. Timing intervals can be triggered by atrial and ventricular events, both paced and sensed. In addition, timing intervals within and between subsequent cardiac cycles can be modified by sensor control.