Prognosis in patients with intra-Hisian conduction disturbances

Tachycardia-dependent second degree AV-block in a patient with right bundle branch block

A 55-year old male patient, with dizzy spells during everyday activity and a complete right bundle branch block as the sole electrocardiographic abnormality, reproducibly demonstrated tachycardia-dependent Mobitz Type II- and 2:1 second degree atrioventricular block. An electrophysiologic study revealed a provocable block within the distal portion of the bundle of His without evidence of a split His potential. Because of the truly tachycardia-dependent AV-block, beta-blocker medication was initiated to prevent high sinus rates during everyday activity. This therapy abolished symptoms totally.

Clinical and electrocardiographic features and long-term results of electrical therapy in patients with isolated His bundle disease

The clinical, ECG, and electrophysiologic findings of 35 consecutive patients with second- and third-degree intra-His block with normal QRS complexes were examined. The follow-up period varied between 12 and 120 months (mean 45). Seventy-seven per cent of the patients were women. Underlying heart disease was present in 43% of the patients. ECGs were characterized by both second-degree type I and type II atrioventricular block, normal or slightly prolonged PR interval of the conducted beats or of the first conducted beat of a Wenckebach sequence, and by subtle changes in the initial forces of the QRS complexes of the escape beats. Electrophysiologic study showed normal sinus and atrioventricular node function and normal infra-His conduction in all patients. In four patients repetitive bradycardia-dependent intra-His block was induced. Thirty-two patients were permanently paced soon after the initial evaluation and three during the follow-up period. Total long-term mortality rate was 23%. None of the patients developed bundle branch block.

Electrophysiologic study of tachycardia-dependent paroxysmal His bundle block in man

Electrophysiologic study was performed in a patient with tachycardia-dependent paroxysmal atrioventricular block. The site of block was within the His bundle. The effective refractory period of the His bundle was markedly prolonged and it was comparable to the critical atrial cycle length producing type II His bundle block. The most likely mechanism of paroxysmal atrioventricular block was repetitive concealed penetration of the blocking zone by nonconducted impulses that reached the proximal His bundle. Enhancing the blocking ratio at the atrioventricular nodal level resulted in improvement of overall atrioventricular conduction.