ABSTRACT
OBJECTIVE - To assess the clinical, electrocardiographic, and electrophysiologic characteristics of patients (pt) with intra-His bundle block undergoing an electrophysiologic study (EPS). METHODS - We analyzed the characteristics of 16 pt with second-degree atrioventricular block and symptoms of syncope or dyspnea, or both, undergoing conventional EPS. RESULTS - Intra-His bundle block was documented in 16 pt during an EPS. In 15 (94 percent) pt, the atrioventricular block was recorded in sinus rhythm; 4 (25 percent) pt had intra-His Wenckebach phenomenon, which correlated with Mobitz I (MI) atrioventricular block on the electrocardiogram. Seven (44 percent) pt had 2:1 atrioventricular block, 2 of whom were asymptomatic (12.5 percent). One (6 percent) pt had intra- and infra-His bundle block. Clinically, 11 (68 percent) pt had syncope or presyncope, 3 (18 percent) had dyspnea on exertion, and 2 (12.5 percent) were asymptomatic. Eight (50 percent) pt had bundle-branch block as follows: 4 (25 percent) pt had left bundle-branch block, and 4 (25 percent) had right bundle-branch block. Left anterosuperior divisional block was observed in 3 pt (19 percent), 2 of whom with associated right bundle-branch block. CONCLUSION - Intra-His bundle block was observed in 11 percent of the pt with second-degree atrioventricular block, syncope or presyncope, or both, it being the most frequent clinical presentation. Intra-His bundle block was more common in the elderly (> 60 years) and among females. The most frequent electrocardiographic presentations were second-degree Mobitz I or type 2:1 atrioventricular block