EFFECTS OF ADENOSINE-TRIPHOSPHATE ON WIDE QRS TACHYCARDIA - ANALYSIS IN 18 PATIENTS

A few studies have indicated that adenosine terminated triggered-activ ity idiopathic ventricular tachycardia, but all involved a small numbe r of cases. The effects of adenosine triphosphate (ATP) on wide QRS ta chycardia have thus not yet been completely clarified. This retrospect ive study was performed to evaluate the therapeutic and diagnostic uti lity of ATP in wide QRS tachycardia. A total of 18 patients with wide QRS tachycardia (QRS width > 120 msec, rate greater than or equal to 1 50 beats/min) were evaluated. ATP, 20-40 mg, was administered intraven ously. An electrophysiological study and treadmill. stress test were p erformed in all patients to elucidate the mechanism of the tachycardia . ATP terminated tachycardia or induced atrio-ventricular block in all 6 patients who had supraventricular tachycardia, but it had no effect on preexcited atrial fibrillation or pre-excited atrial flutter. Vent ricular tachycardia was terminated by ATP in 5 of the 10 patients. In 4 of these 5 patients, the focus of the tachycardia was the right vent ricular outflow tract. No entrainment phenomenon was demonstrated by e lectrophysiological study with induction of the tachycardia by stress test or isoproterenol infusion, suggesting the contribution of trigger ed activity to the tachycardia. In the remaining patient with complete right bundle branch block type tachycardia with right axis deviation, the mechanism of ventricular tachycardia could not be determined. In the 5 patients in whom ATP failed to terminate ventricular tachycardia , the reentry mechanism was suggested by the presence of entrainment p henomenon depicted on electrophysiological study. In summary, this stu dy suggests that ATP terminates supraventricular wide QRS tachycardia and ventricular tachycardia due to triggered-activity, but that it has no effect on pre-excited atrial fibrillation or flutter or on ventric ular tachycardia due to a reentry mechanism. These findings add to the mounting evidence regarding the therapeutic and diagnostic utility of ATP in wide QRS tachycardia.