Electrophysiologic observations in a patient with bradycardia-dependent atrioventricular block

Paroxysmal atrioventricular block: clinical experience with 20 patients

BACKGROUND

Paroxysmal atrioventricular (AV) block is an ill-defined entity, previously described in sporadic cases in association with vasovagal reaction, coronary angiography and distal conduction disease.

METHODS

We describe 20 patients (10 women) aged 26 to 80 years with symptomatic paroxysmal AV block.

RESULTS

Eight patients had ischemic heart disease-three with dilated cardiomyopathy, and two with co-existing carotid sinus hypersensitivity. Eight were taking chronic AV blockers. In five patients, the paroxysmal AV block occurred during a vagal reaction, in one during migranotic headaches, in one following aortic valve replacement and in one while recovering from acute myocardial infarction. The events lasted between 2.2 and 36 s. In 10 patients, the QRS configuration on the electrocardiogram was wide. Immediate treatment consisted of intravenous atropine and fluid supplements in two patients, discontinuation of the AV blocking agents in four, and the insertion of a temporary pacemaker in eight. Seventeen patients required a permanent pacemaker.

CONCLUSIONS

Paroxysmal AV block is an underestimated clinical entity related to vagal reaction, AV blocking drugs and distal conduction disease. Most of our patients eventually required implantation of a permanent pacemaker.

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.

Symptomatic spontaneous paroxysmal AV nodal block due to localized hyperresponsiveness of the AV node to vagotonic reflexes

Two apparently healthy patients had recurrent syncope with documented paroxysmal AV block. In both patients the site of AV block was demonstrated to be in the AV node. Coronary angiography (in both patients) and sustained deep inspiration (one patient) reproducibly initiated episodes of paroxysmal AV nodal block (identical to spontaneous episodes). Atropine abolished further attempts of AV block induction. Vagal hyperresponsiveness was limited to the AV node, since the interventions provoking paroxysmal AV nodal block produced only appropriate sinus slowing. This syndrome reflects hyperresponsiveness of the AV node to vagotonic reflexes, and exists as a clinically significant entity producing recurrent syncope.