Idiopathic paroxysmal AV block due to low baseline adenosine levels and heightened receptor sensitivity

This is a fairly recently described entity:

Idiopathic paroxysmal AV block poses a true diagnostic challenge. Although it is true that the clinical presentation does not differ from that of another cardiogenic syncope, the diagnosis of this block requires the lack of a structural cardiac pathology that justifies the observed manifestations and an absence of electrocardiographic disorders prior to an episode. For diagnosis, it is useful the implantable loop recorder to substantiate AV block paroxysms and assess their clinical correlations.

The mechanism associated with idiopathic paroxysmal AV block is unknown. It has been postulated that patients with low basal adenosine levels exhibit hyperaffinity of the adenosine receptors of the AV node. No relevant data have been reported, so it´s necessary that more studies are needed to confirm this hypothesis.

The prognosis of idiopathic paroxysmal AV block is favorable, given the paroxysmal profile of the AV block and the low probability of degeneration into permanent forms of AV block. Permanent stimulation devices can be employed to prevent and avoid the recurrence of syncopal episodes in patients with idiopathic paroxysmal AV block.