Mechanism-specific effects of adenosine on atrial tachycardia.

Abstract

BACKGROUND Recent reports suggest that adenosine, in addition to terminating supraventricular tachycardia involving the atrioventricular (AV) node, may have antiarrhythmic effects on atrial tachycardia. The electrophysiological effects of adenosine on supraventricular tissue include shortening of action potential duration in atrial myocytes mediated by the potassium current, IKACh,Ado; shortening of action potential duration and hyperpolarization in sinus node cells; and anti-adrenergic electrophysiological effects resulting from inhibition of adenylyl cyclase. We therefore hypothesized that the response of atrial tachycardia to adenosine would be mechanism specific, with termination of atrial tachycardia due to sinus node reentry or cAMP-mediated triggered activity, transient suppression of automatic atrial tachycardia, and an absence of antiarrhythmic effect on tachycardia due to intraatrial reentry. METHODS AND RESULTS Adenosine (mean +/- SD, 143 +/- 54 micrograms/kg IV) was administered to 27 patients (55 +/- 19 years) in atrial tachycardia whose mechanism was confirmed by electrophysiological study. Adenosine terminated sinus node reentrant tachycardia in 6 of 6 patients and terminated atrial tachycardia due to triggered activity in the 1 patient in whom it was identified. Adenosine transiently suppressed automatic atrial tachycardia in 7 of 7 patients and had no effect in 13 patients with intra-atrial reentrant tachycardia, including 8 patients with atrial flutter. CONCLUSIONS These findings demonstrate that adenosine's effects on atrial tachycardia are mechanism specific and can be used to differentiate between reentrant tachycardia confined to the region of the sinus node or atria and between nonreentrant atrial tachycardia due to either triggered activity or automaticity.

Response to Adenosine Differentiates Focal From Macroreentrant Atrial Tachycardia

“…Focal AT consistent with enhanced automaticity had the following characteristics 3 : spontaneous initiation or termination, failure to initiate with programmed stimulation, and demonstration of warm-up and cool-down phenomena. In contrast, focal AT consistent with triggered activity demonstrated reproducible initiation and termination with programmed stimulation, as well as sensitivity to adenosine and verapamil (when administered).…”

“…We have previously demonstrated that atrial flutter is insensitive to adenosine. 3 Like atrial flutter, incisional ATs do not terminate with adenosine. The exception to this rule is the rare form of macroreentrant AT involving tissue with decremental conduction properties.…”

“…We previously proposed that adenosine has mechanismspecific effects on atrial tachycardia, 3,4 such that it terminates or suppresses focal AT (attributable to triggered activity or enhanced automaticity, respectively) and has no effect on macroreentrant AT (with the rare exception of that involving partially depolarized tissue). 5 The effect of adenosine on reentrant AT remains controversial, however, because other studies 6,7 have reported termination with adenosine in up to 90% of patients.…”

Antiarrhythmic Medications for Cardioversion and Maintenance of Sinus Rhythm in Patients with Cardiac Arrhythmias: A Review of the Literature

“…The drug terminates the vast majority of AV node dependent tachycardias producing AV block that will reveal intratrial arrhythmias. DiMarco et al demonstrated high specificity and sensitivity as well as safety of adenosine in the diagnosis of patients presenting with narrow-complex tachycardia by distinguishing between atrial tachycardias and those that require the AV node [122,123].…”

Adenosine and Atrial Tachycardia

“…Lerman et al have previously explored these various possibilities and found that adenosine infusion helped distinguish between the various mechanisms responsible for AT in patients. 4,5 In this issue of the Journal, Dr Lerman and his colleagues present their experience with adenosine in delineating the mechanism of AT in a large series of patients. 6 Among the 59 patients, approximately one third had undergone a prior procedure for either AF or AT.…”