[Exogenous adenosine as an anti-arrhythmia agent].

Adenosine has potent cardiac electrophysiologic effects including a negative chronotropic action on the sinus node and a predominant negative dromotropic action on the AV node. The latter property has mainly led to the use of adenosine as antiarrhythmic agent for the acute management of paroxysmal supraventricular tachycardia (PSVT) mediated by a reentrant mechanism involving the AV node. The effects of adenosine are dose-dependent and of very short duration since the half-life is less than 10s. The efficacy rates for termination of AV reentrant tachycardias were found to be 35% with 3 mg, 60-70% with 6 mg, 80% with 9 mg, and 90-95% with 12 mg adenosine. The AV nodal depressant effects of adenosine have also been used for determining the mechanism of wide QRS tachycardias for differentiating supraventricular tachyarrhythmias with aberrant conduction from ventricular tachycardia. Adenosine either terminates or slows almost all types of supraventricular tachyarrhythmias or it leads to unmasking of the underlying mechanism such as atrial flutter with aberrant conduction. One form of ventricular tachycardia, the idiopathic type originating from the right ventricular outflow tract can usually be terminated with adenosine due to its cAMP-mediated mechanism. Adenosine is helpful to detect or to increase preexcitation which is important for planning a catheter ablation procedure since the preexcitation pattern allows to localize the accessory pathway. Since the action of adenosine usually does not alter the accessory pathway conduction it is also useful for control ablation efficacy noninvasively in terms of antegrade conduction and during ventricular pacing for the retrograde conduction. Further evaluation and research is necessary for better understanding of adenosine action on the human atrial electrophysiology since it provokes atrial fibrillation in some patients, and of adenosine action on the different pathways in AV nodal reentrant tachycardias and some accessory pathways with decremental (AV nodal-like) conduction properties.