Abstract
Adenosine is an effective, safe drug for the diagnosis and treatment of paroxysmal tachycardias in adult and pediatric patients. A starting dose of 0.05-0.10 mg/kg as a rapid bolus injection is recommended for infants and children. An electrophysiologic effect can be expected within 20 seconds after injection. Dosage may be increased up to 0.3 mg/kg in steps of 0.05-0.10 mg/kg or until conversion to sinus rhythm is reached. Due to its basic electrophysiologic properties of slowing conduction in the atrioventricular (AV) node, which may result in transient AV block, adenosine is almost always effective in terminating supraventricular tachycardias in which the AV node forms a critical part of the reentrant circuit (i.e., AV nodal reentrant tachycardia and AV reciprocating tachycardia). Based on its properties, adenosine is also advocated as a useful diagnostic tool for unmasking primary atrial tachycardias by inducing transient high grade AV block. Advantages over other antiarrhythmic agents include the agent's short half-life (<2 seconds) and minimal or no negative influence on blood pressure. Because of its short half-life, however, early recurrence of the tachycardia is observed in up to one-third of patients treated. Based on rare but serious unwanted side effects, patients with known or suspected irritable airways and sinus node dysfunction and those who have undergone orthotopic cardiac transplantation should probably not be given adenosine. Adenosine may be recommended as the drug of choice for treatment of paroxysmal tachycardia in young patients. Primary success rates range between 85% and 100% of all the tachycardia episodes treated. Termination of the tachydysrhythmia, however, does not always mean that the underlying dysrhythmia was of supraventricular origin with the AV node as a critical part of the tachycardia mechanism. Rare but possible life-threatening side effects (prolonged sinus arrest and complete AV block, atrial fibrillation, acceleration of ventricular tachycardia, apnea) necessitate proper monitoring of the patients.