Pacemaker dependency after coronary artery bypass.

A retrospective study was carried out on 36 patients (33 males and 3 females) to determine the incidence of VVI pacemaker dependency following coronary artery bypass surgery. Pacemaker dependency was defined as the presence of pacemaker activity when pacing rate was programmed at 50 beats/min and/or when no hemodynamic adequate rhythm was present during pulse generator replacement. The patients were divided into two groups: (group I) 26 patients with complete atrioventricular (AV) block developing in the early postoperative period. In most of them a pacemaker was implanted up to 3 weeks following surgery (range 2 days to 1 year); (group II) ten patients in whom the indication for pacemaker implantation was sick sinus syndrome with sinus arrest and/or tachy-bradycardia. These patients underwent pacemaker implantation at varying periods of time following surgery (range 12 days to 4 years). Unipolar endocardial leads with VVI programmable pacemakers were implanted in all patients included in this study. Mean follow-up time was 3 years. In group I the pacemaker dependency rate was 65%, whereas in group II it was 30% throughout the follow-up period. It is concluded that the low incidence of pacemaker dependency in patients who undergo pacemaker implantation after coronary bypass surgery necessitates frequent evaluation in the nondependent patient, in order to reassess the need for the pacemaker before pulse generator replacement. Such reassessment should probably include prolonged ambulatory monitoring as well as invasive evaluation of the conduction system, if avoidance of pulse generator replacement is considered.