Can Adenosine 5′-Triphosphate Be Used to Select Treatment in Severe Vasovagal Syndrome?

Abstract

The vagal effect of ATP may identify the subgroup of patients at high risk of severe cardioinhibitory response of vagal origin who likely will benefit from pacemaker therapy. This fast, uncomplicated test should be considered for further use in screening patients with vasovagal syndrome.

Syncope

“…66 Administration of intravenous ATP with unexplained syncope has been studied with conflicting results. A positive response is variably defined as either a pause (AV or SA block) greater than 10 seconds (ignoring escape beats) 73 or an R-R interval >6 seconds. 43,44 A positive ATP test correlates poorly with the mechanism of spontaneous syncope as documented by ILR, 43,44 but patients with unexplained syncope with a positive ATP test had a better response to dual chamber pacing than those with a negative test.…”

Guidelines on management (diagnosis and treatment) of syncope

“…Intravenous injection of adenosine triphosphate (ATP) has recently been proposed as a tool in the investigation of patients with unexplained syncope [204,205] . In predisposed patients with unexplained syncope, the stimulation of purinergic receptors, with a powerful dromotropic effect on the atrioventricular node [206] , causes prolonged ventricular pauses due to atrioventricular block, which are considered as possibly responsible for spontaneous attacks.…”

“…The protocol proposed by Flammang et al [204] consists of the injection in a brachial vein of a bolus (<2 s) of 20 mg of ATP followed by a 20 ml flush of dextrose solution or dissolved in 10 ml of saline solution. During injection, patients remain supine with continuous electrocardiographic recordings just before and 2 min after drug administration.…”

“…Interpretation of the result of the test is exclusively based on the duration of the cardiac 'pause'. A value of >6 s [205] or >10 s even if interrupted by some escape beats [204] is defined as abnormal (level B). Such pauses were observed in about 5% of control subjects without syncope.…”

Pharmacotherapy of Neurally Mediated Syncope

“…4 -8 ATP and adenosine have also been found to unmask susceptibility to neurally mediated paroxysmal AV block, one of the important electrocardiographic manifestations of cardioinhibitory neurally mediated syncope. 9,10 In regard to treatment, drugs may be used for both emergent resuscitation of severely hypotensive and bradycardic victims (eg, dopamine, norepinephrine, anticholinergics), as well as for long-term prevention of syncope recurrences. The resuscitation role is a relatively rare occurrence, being perhaps most often encountered during the course of an acute inferior wall myocardial infarction complicated by triggering of the Bezold-Jarisch reflex.…”