Pharmacological testing in the diagnosis of arrhythmias.

Pharmacological testing has several indications in the diagnosis of arrhythmia. It is used for the diagnosis of bradycardia-related syncope either during non invasive tests as adenosine triphosphate (ATP) for the diagnosis of vasovagal syncope, but also for the diagnosis of sick sinus syndrome or isoproterenol infusion during the head up tilt test to induce a vasovagal syncope or during electrophysiological study to look for infrahisian AV block or organic sick sinus syndrome after injection of Ajmaline or to know if sick sinus syndrome or suprahisian AV block are reversible after atropine and are vagal-related. It is used for the diagnosis of supraventricular and ventricular tachycardia; isoproterenol is largely used generally during electrophysiological study. The infusion of isoproterenol is required in exercise-related arrhythmias, in arrhythmogenic right ventricular cardiomyopathy, in idiopathic ventricular tachycardia and in idiopathic dilated cardiomyopathy. ATP can be used to induce a vagal-related atrial fibrillation and may help to differentiate a reentry through accessory pathway or AV nodal re-entrant tachycardia. It is used for the detection and the evaluation of prognosis of some diseases at risk of sudden death. Isoproterenol infusion is required in the preexcitation syndrome to look for the shortening of accessory refractory period. Ajmaline or flecaïnide injection is mandatory in the family of a patient with a Brugada syndrome to detect the disease.