COMPARATIVE-EVALUATION OF BIPOLAR ATRIAL ELECTROGRAM AMPLITUDE DURINGEVERYDAY ACTIVITIES - ATRIAL ACTIVE FIXATION VERSUS 2 TYPES OF SINGLE-PASS VDD R LEADS/

Endocardial P wave amplitude (PWA) is an important determinant of the atrial sensing capabilities of an atrial-based pacing system. Although changes in PWA during physical activities are known to occur in DDD/R pacing, there is little information on the P wave stability in single pass lead VDD/R pacemakers using floating P wave sensing. We investig ated the variation of PWA during daily life activities using telemetry recorded atrial electrograms in 21 patients with DDDR pacemakers (Rel ay or Elite) and 29 patients with single lead VDD/ R pacemakers (Unify or Thera). Physical activities resulted in marked individual variabil ity of PWA but, as a group, there was no significant difference betwee n PWA during sitting, standing, lying down, and coughing in both DDDR and VDD/R pacing. In the Elite II pacemaker, walking at 2 miles per ho ur resulted in significant reduction of PWA (11.6% compared with sitti ng, P < 0.05). The most consistent reduction in PWA occurred in the re laxation phase of the Valsalva maneuver (VM), with all pacemakers show ing a reduction in PWA (mean reduction in PWA compared with sitting in DDDR and VDD/R were 16.6% and 12.8%, respectively). Two patients with DDDR pacemakers (Relay) and three patients with VDD/R pacemakers (1 U nity and 2 Thera) had atrial sensing failure during VM or walking. In conclusion, large variation in PWA occurs during daily life activities . The extent of variation is dependent on the patients, types of atria l lead, and the maneuvers performed. A twice sensing threshold may be insufficient to ensure adequate atrial sensing during these activities . The VM, which effects a consistent change in intracardiac volume, is the most reliable method for bedside evaluation of the lower end of s ensitivity margin.