[Mobitz type II 2d degree atrioventricular block. Clinical and electrophysiological study].

His Bundle Electrogram (HBE) was recorded in 20 patients with Mobitz type II block. All patients were clinically evaluated and a history of syncope was carefully investigated. These patients were prospectively followed (mean follow up: 20,4 months). ECG showed LBBB in 9 patients, RBBB + LAHI in 6, RBBB + LPH in 3, LAH in 1, left axis deviation in 1. In all patients HBE revealed prolungation of H-Q interval and localization of block within the His-Purkinje system (within H in 4) distal to H in 16. In 9 patients intermittent complete heart block localized within the H-P system was documented during HBE recording. 15 patients (75%) experienced syncopal attacks. All patients underwent implantation of permanent demand pace-maker, without further episodes of syncope. Since the site of block is the most important determinant of prognosis, in all patients with Mobitz type II block, whether or not symptoms are present, prophylactic implantation of pace-maker is indicated, because high incidence of progression to complete heart block, with potential risk of Adams-Stokes syndrome and sudden death.