Effect of different location of atrial lead position on nearfield and farfield electrograms in dual chamber pacemaker-defibrillators

The normal functioning of dual chamber pacemaker-cardioverter defibrillator (AV pacer/ICD) may be affected by oversensing of the farfield R wave (FFRW ) by the atrial channel. This study aimed to investigate whether placement of the AV pacer/ICD's atrial lead at a lateral (LAT) wall location compared to a medial (MED) location i.e. the appendage of the right atrium, would r educe the amplitude of FFRWs but not the nearfield atrial electrograms (AEG Ms) during sinus rhythm (SR) and ventricular fibrillation (VF). In 17 patie nts, real time electrograms were recorded during SR and induced VF through the atrial lead initially at the MED and subsequently at the LAT location. In 10 patients the electrograms in SR were also recorded on a computerized data acquisition and recording system at different band-pass filter setting s. Although FFRWs were recorded both at MED and LAT locations, they were mu ch smaller, 3.5 +/-4.1[emsp4 ]mm during SR and 1.7 +/-2.2 mm during VF at t he LAT location. At 30-500 Hz band-pass filter, lower amplitudes of FFRWs 0 .14 +/-0.09 mV were recorded at the LAT location. The V/A ratios of the amp litudes of FFRWs and AEGMs were smaller at the LAT location during SR and V F. The nearfield AEGMs were of similar amplitudes at the MED and LAT locati ons. These data indicate that lower amplitudes of FFRWs are recorded by pla cement of the atrial lead at the lateral wall of the right atrium. Oversens ing of FFRWs may be prevented to improve functioning of the AV pacer-ICD.