Five cases of complete atrioventricular block induced by bending forward: unusual but not unique

We describe five patients with syncope caused by a complete atrioventricular block (AVB) while they were bending forward, not rising after bending, and aim to describe the occurrence and the association between bending forward and AVB.

In two patients, bending forward was the exclusive trigger for syncope, while in the remaining three, other postural changes (sitting down, standing up, and exertion) could also provoke syncope. Complete AVB as the cause of syncope was documented using ECG monitoring in two cases and an implantable loop recorder in the other three. Ectopic beats without preceding sinus slowing occurred before syncope in four cases. Two cases had a left bundle branch block. All patients responded favourably to cardiac pacing.

This is the first case series on complete AVB provoked by bending forward. Syncope during bending forward should suggest a search for an AVB. Arguments in favour of a vagal mechanism were syncope triggered by bending forward, and that other triggers could also evoke syncope. However, the absence of sinus slowing before syncope in some cases and the fact that bending forward did not seem to provoke reflex syncope without AVB, cast doubts on a reflex mechanism. There were also arguments favouring conduction disorder: i.e. ectopic beats before syncope and pre-existing conduction disturbances in two cases. The cases are reminiscent of paroxysmal AVB. Discrimination between paroxysmal AVB and vagal AVB is important because a pacemaker is warranted in arrhythmic complete AVB, while the benefit is limited or absent in reflex AVB.