Spontaneous heart activity in pacemaker treated patients with high-grade atrioventricular block. A Holter monitor...

A Holter monitor study was performed to assess the occurrence of spontaneous heart activity in 70 pacemaker treated patients (mean age 72.1 years) with high-grade atrioventricular (AV) block, who have been treated with permanent pacemakers for a mean of 60 months (range 5-161). Nineteen patients had asynchronous (VOO), and 51 QRS-inhibited (VVI) pacemakers. The patients were monitored for a mean of 23 hours (range 15.5-26). Twenty-five patients were re-studied for day-by-day variations in spontaneous heart activity. At clinical observation, thirty-eight patients had some kind of spontaneous cardiac activity, mostly ventricular ectopic beats. Three patients had short episodes of sinus rhythm of more than 70 beats/min. Patients in functional class III-IV (NYHA) or with an enlarged heart had the most spontaneous heart activity. No tachyarrhythmias precipitated by interference between intrinsic heart beats and asynchronous pacemakers were seen. Twenty patients studied twice had a relatively stable occurrence of spontaneous heart activity, while five (20%) varied considerably. On the basis of these long-term observations it is difficult to predict when interference rhythm will occur, and asynchronous pacemakers therefore cannot be recommended for the first implantation.