Intravenous adenosine during atrioventricular nodal reentrant tachycardia - induction of atrial fibrillation with rapid conduction over an accessory pathway: unmasking of a concomitant Wolff-Parkinson-White syndrome

The antiarrhythmic properties of adenosine, its ultrashort half-life: and t he absence of Frequent serious side effects make it a Front-line agent in a rrhythmia management, especially in the treatment of atrioventricular nodal reentrant tachycardia. Due to a shortening of atrial refractoriness, adeno sine can facilitate the induction of atrial fibrillation. Life threatening tachycardias may result from a potential rapid conduction of atrial fibrill ation over an accessory pathway especially if the latter one has a short an tegrade refractory period. We report a case of a 59 year old female patient in which intravenous admin istration of adenosine during typical atrioventricular nodal reentrant tach ycardia was followed by atrial fibrillation with rapid conduction over a hi therto unknown accessory pathway. After intravenous administration of adenosine the tachycardia was terminate d successfully within 38 s. After a short period of asystole, spontaneous a trial fibrillation developed unmasking an antegrade preexcitation with subs equent rapid ventricular response (210 b/min). The three-lead ECG showed a narrow QRS complex tachycardia. Because of spontaneous conversion to sinus rhythm and the absence of hemodynamic compromise there was no need for exte rnal cardioversion. During electrophysiological study an antidromic atrioventricular reentrant tachycardia was recorded over a left posteroseptal accessory pathway includ ing antegrade conduction properties only. Because of its ultrashort half-life, serious side effects after adenosine a dministration are rare. The possibility of life threatening proarrhythmias after intravenous adenosine administration should be taken into considerati on if the etiology of a paroxysmal supraventricular tachycardia is not clea r and a concomitant Wolff-Parkinson-White syndrome cannot be excluded. As with application of all intravenous antiarrhythmic agents, the administr ation of adenosine should only be performed if continuous ECG monitoring an d cardioversion facilities are available and possible.