Intra-His bundle block in acute myocardial infarction. Report of two cases.

Two patients with acute intra-His bundle block, both secondary to myocardial infarction, are described. The diagnosis of the block was proved by means of His bundle recordings during the phase of complete atrio-ventricular (A-V) block. Two His bundle potentials, one (H) following each A wave and the other (H') preceding each QRS complex, were detected. In both cases, as well as in the few cases reported in the literature, the site of the infarction was in the inferior wall, an occurrence which shows the functional importance of the posterior blood supply to the His bundle. In both cases the block developed into a chronic form, requiring the implantation of a transvenous pacemaker in one case. This evolution suggests that the post-infarction intra-His bundle block may be due to irreversible anatomic damage.