Double-Counting of Intracardiac Electrogram During Biatrial Pacing

Abstract

lthough atrial fibrillation (AF) is the most commonly encountered arrhythmia and is associated with a high incidence of stroke and increased cardiovascular mortality, 1,2 in many cases it is still difficult to treat. Previous studies argued that multisite atrial pacing may prevent the recurrence of AF, [3][4][5][6][7][8][9][10] but in the application of biatrial pacing, we have often found double-counting of the intracardiac electrogram in the atrium because of interatrial conduction delay. The slow conduction in the right atrium and retrograde left atrial activation result in inhomogeneous activation of the left atrium and intra-and interatrial asynchrony. This conduction delay is important relation to the mechanisms that underlie AF, and the majority of patients with interatrial conduction delay have a high incidence of atrial tachyarrhythmias. 11 In the present study, we evaluated double-counting of the intracardiac electrogram in the atrium and used it to estimate the atrial pacing threshold. Methods Study PopulationThe study group comprised 10 patients (5 men, 5 women; Pacemaker ImplantationBiatrial dual-chamber pacemaker implantation was performed. The cephalic vein was used whenever possible, and the other 2 leads were inserted into the axillary vein by percutaneous puncture. First, the left atrial lead was introduced and positioned in the distal or mid site of the coronary sinus. After the lead was fixed, the ventricular lead and right atrial lead were introduced with passive fixation. We used the unipolar lead for the left atrium, and the bipolar leads for the right atrium and ventricle. The interelectrode distance of the bipolar lead was 17 mm. The coronary sinus lead was connected to the anodal port of the Y-connector and the distal electrode of the right atrial lead to the cathodal port. The connector was inserted into the atrial port of a DDDR pacemaker (Thera DR™ or Kappa™. Medtronic, Minneapolis, MN, USA). The ventricular lead was inserted into the ventricular port. The generator was positioned in the prepectoral pocket and the pocket was closed. Patient Follow-upArrhythmia control and device performance were assessed at outpatient visits. Intracardiac electrograms were recorded using the memory function of the implanted pacemaker devices, and the biatrial pacing threshold was checked. Background Biatrial pacing has a significant problem with memory function that misinterprets normal sinus rhythm as atrial tachyarrhythmias and in addition estimation of the atrial pacing thresholds (biatrial and uniatrial pacing thresholds) is sometimes difficult because of small P waves. Methods and ResultsThe intracardiac electrograms recorded by a pacemaker in 10 patients (age, 66.7±10.7 (SD) years) with implanted biatrial pacemakers were analyzed. Atrial sensing within the atrial refractory period after atrial pacing was counted in 6 of the 10 patients (timing of the double counting was 143±64 ms) when pacing failed in the left or right atrium. Atrial sensing within the atrial refractory period after atrial pa...