Prospective observations in patients with chronic bundle branch block and marked HV prolongation

Eighteen of 388 patients with chronic bundle branch block, studied electrophysiologically and followed prospectively, had H V intervals of 80 msec or greater. Five patients were functional class I, 5 class II, 7 class III, and 1 class IV. Followup ranged from 103 to 1919 days (mean 711±118). Three patients needed permanent pacing for the following indications: sino atrial block, sinus bradycardia postcardiac surgery, and 2° block distal to the His bundle. Six patients died, three suddenly. The five initially asymptomatic patients are alive and without pacemakers (mean followup 732±139 days). Although marked H V prolongation was associated with high morbidity and mortality in this small series, this was only in patients with symptomatic heart disease. The asymptomatic patients had a benign clinical course. Prophylactic pacing would probably not modify clinical course in the former group, and is probably not indicated in the latter group. Longer followup will be needed for definitive prognostication.