Rate-responsive pacing as compared to fixed-rate VVI pacing in patients after ablation of the atrioventricular conduction system

In 44 patients with supraventricular arrhythmias various pacemakers were studied after closed-chest ablation of the atrioventricular conduction system. There were 22 patients with a rate-programmable VVI pacemaker (Group I), 15 patients with an activity mode (ACTIVITRAX 8400) (Group II) and seven patients with a QT-mode pacemaker (QUINTECH 911) (Group III). To study both physical work capacity and heart-rate behaviour, exercise testing was performed using a treadmill. Sixteen patients in Group I (72.7%) complained of shortness of breath during exercise in comparison to four patients (26.7%) in Group II and three patients (42.9%) in Group III. Normal physical work capacity was observed in three of 22 patients (13.6%) in Group I and in all patients in Groups II and III. The heart rate both increased and decreased more rapidly at the onset and end of the stress test, respectively, in patients with activity-mode compared to patients with QT-mode pacing systems. These data show that, despite successful His-bundle ablation, both dyspnea and decreased work capacity are observed when VVI pacemakers are used. In contrast, the use of rate-responsive pacing systems leads to better cardiac performance.