Factors influencing prognosis of bundle branch block complicating acute antero-septal infarction. The value of his bundle recordings.

Of 50 consecutive patients with bundle branch block (BBB) complicating acute antero-septal infarction, 37 died in hospital. Patients with BBB of delayed onset or BBB of short duration had a significantly lower mortality. His bundle recordings were made in 35 patients without pulmonary edema or shock at the time of appearance of BBB. Thirteen of 16 patients with prolonged H-V intervals died compared to nine of 19 with normal H-V intervals (P < 0.05). In patients with bifascicular block, 11 of 15 with prolonged H-V intervals developed complete A-V block compared to one of ten with normal H-V intervals (P < 0.005). Twenty-five of 33 patients with normal P-R intervals died compared to eight of 12 with first degree A-V block. Seven of 15 patients with prolonged H-V intervals had normal P-R intervals and four of these seven developed complete A-V block. We conclude that the length of P-R interval has no prognostic significance and is of limited value in predicting both prolonged H-V interval and development of complete A-V block. In contrast, His bundle recordings are of value in identifying patients with BBB complicating antero-septal infarction who are at immediate high risk for development of complete A-V block and death.