Short-term effects of atrial versus atrio-ventricular pacing on myocardial ischaemia in coronary artery disease patients.

This investigation was undertaken to evaluate the effects of short-term atrial vs atrio-ventricular pacing on myocardial ischaemia. The study was in two parts. In part one, 12 coronary artery disease patients were studied to investigate the effects of the two pacing modes on angina pectoris, coronary sinus O2 saturation and lactate. The two pacing modes were each applied for 5 min at 25 beats.min-1 more than the maximum heart rate of the exercise test. Coronary sinus O2 saturation and lactate were estimated before and after pacing. In part two, 13 patients with left anterior descending coronary artery disease were studied to investigate the effects of the two pacing modes on coronary flow reserve, using a Doppler catheter in the above mentioned branch after the administration of 10 mg intracoronary papaverine. The pacing rate was 15 beats.min-1 greater than the resting heart rate. Coronary sinus lactate and O2 saturation changes were the same and angina pectoris developed at about the same time from the beginning of pacing under both modes. Coronary flow reserve was 2.1 +/- 0.7 during atrial pacing and 2.1 +/- 1.1 during atrio-ventricular pacing (ns). It is concluded that short-term atrial and atrio-ventricular pacing have the same effects on myocardial ischaemia in coronary artery disease patients.