Exercise capacity and spontaneous heart rhythm after transvenous fulguration of atrioventricular conduction.

Twenty nine patients who had had refractory supraventricular tachycardia were studied 4-36 (mean 16) months after transvenous fulguration of the atrioventricular junction. Twenty two had complete atrioventricular block, five partial atrioventricular block, and two had atrioventricular conduction via an accessory atrioventricular pathway. Though all patients were free of palpitation after the procedure, exertional dyspnoea had developed in 13 and in two patients pre-existing dyspnoea had worsened. During ventricular demand pacing, exercise time was reduced to 43% of the predicted value for their age and sex. The 16 patients with rate responsive pacemakers demonstrated a significantly better but still impaired exercise capacity during "physiological" pacing as compared with their performance during constant rate pacing. In patients with complete atrioventricular block there was an increase in spontaneous ventricular rate during exercise in seven patients and in response to the Valsalva manoeuvre in eight patients. This suggests that the intrinsic ventricular pacemaker is influenced by autonomic nervous system activity in some patients. It is concluded that though transvenous fulguration is successful in controlling tachycardia it may reduce exercise capacity. Most patients remain in complete atrioventricular block after the procedure and, in contrast with the practice as described in early reports, would benefit from "physiological" pacing--though even with this mode exercise capacity is likely to be abnormal.