Intraventricular trifascicular block. Observations on conduction disturbance in bundle-branch system.

A case of intraventricular trifascicular block secondary to an inferior myocardial infarction is reported.The case denonstrates instances of 2: I atrioventricular conduction due to alternating block in the right bundle-branch and block in the right bundle and both anterior and posterior divisions of the left bundle (trifascicular block).Instances of I: i A V conduction with grade I block and periods of type I (Mobitz) block are ascribed to a delayed and a Wenckebach type of conduction respectively in the posterior division of the left bundle.Recent recognition of the trifascicular nature of the bundle-branch system has changed some of the concepts about AV conduction disturbances and the pathways of impulse propagation in the ventricular myocardium.In a recent review by Rosenbaum et al. (I969) no more than 20 cases of intraventricular trifascicular block were found while the authors recognized the various combinations that may arise secondary to the different grades of conduction disturbance in the three fascicles of the bundle-branch system.The following report deals with a further case of intraventricular trifascicular block and pre- sents certain features of interest where differ- ent grades of AV conduction disturbance are explained on the basis of variable dysfunction of the three fascicles of the bundle-branch system. Case reportA 54-year-old man was admitted to Kasr El-Aini Faculty of Medicine of Cairo University on March 1960.The patient, who was known to have diabetes and hypertension for some time, began to complain of anginal attacks one week before admission.The attacks were frequent, not always related to exertion, and lasted from a few up to