Mechanisms for Adams-Stokes syndrome in patients with artioventricular block : clinical electrophysiological significance of paroxysmal artioventricular block

Mechnisms responsible for the occurrence of Adams-Stokes syndrome in 85 Patients with atrioventricular (AV) block were studied through the examination of their clinical symptom and course, documented ECG findings and electrophysiologic approaches. Patients with 1st and 2nd degree AV block in the His-Purkinje system had a high incidence of syncopal sttack (8 of 10 patients) and this incidence was alomost equal with that in patients with 3rd　degree of AV block in the His-Puurije system. Twentyfive 0f 61 patients (41%) with 3rd degree AV block had history of syncope, the mechanisms of which were nor revwaled other than in 3 cases with a history of paroxysmal AV block, 2 cases of block in block and 3 cases of Torsade de Pointes. There was no significant differrence between in patients with and without a history of Adams- Stokes attack in parameters of subsidiary pacemaker automaticity (heart rate of escape rhythm nad automaticity recovery time) in patients with 3rd degree AV blok. Paroxysmal AV block in the His-Purkinje system, associated with phase 3 and/or phase 4 block, has been suggested have a determinant role in the mechanism for Adams-Stokes syndromes in the stage of transitional phase of 1st and 2nd to 3rd degree of AV block.