Rate dependent bundle branch block

ABSTRACT

Eight cases of intermittent bundle branch block showing rate dependence are presented. Six cases were tachycardia dependent, one bradycardia dependent and one case showed both Right Bundle Branch Block and Left Bundle Branch Block at different rates. Tachycardia - dependent bundle branch block was explained on the basis of cycle-length recovery time relation and revealed a critical rate for normal intraventricular conduction. Bradycardia - dependent bundle branch block was best explained on the basis of enhanced phase-4 depolarisation of the bundle branch block system. Ischemic heart disease and Hypertension appeared to be the most important aetiological factors. The appearance of intermittent bundle branch block in younger age groups could be a marker of ischaemic heart disease developing in the later part of life