Paroxysmal Complete Atrioventricular Block: Who is the True Culprit?

A 60-year-old woman was presented with unexpected syncope in the emergency department. After performing a serious of examinations, we obtained that intact paroxysmal atrioventricular block (AVB) was the culprit. Moreover, 24h Holter monitoring showed complete paroxysmal AVB occurred in no special conditions, having nothing to do with pause-dependent 4 phase block, 3 phase block, premature beats, Mobitz type II AVB and rate-related heart beats. Our report is entirely different from the present submitted research. We performed electrophysiological study to testify our thought. The intracardiac electrogram showed that AVB existed in mid-distal location of His-Purkinje system, which had a decreased voltage-gated sodium channel availability and then sinus impulse conducted to ventricle was prevented.

The most outstanding feature of our study different from other reports is that the whole probable factors contributing to intermittent AVB occurred in the same patient. Nevertheless, other reports revealed the above phenomena referred to different patients. It is reasonable for us to regard variable factors inducing paroxysmal AVB as a coincidence.