EFFECT OF ADENOSINE OR ADENOSINE-TRIPHOSPHATE ON ANTIDROMIC TACHYCARDIA

Objectives. This study was designed to determine the effect of adenosi ne or adenosine triphosphate (ATP) on antidromic tachycardia. Backgrou nd. Adenosine and adenosine triphosphate are useful for differential d iagnosis of wide QRS tachycardia. It has been believed that tachycardi a termination caused by these agents is due to the preferential depres sive effect on the atrioventricular (AV) node, whereas their effect on accessory pathways is minimal. Methods. We studied the effect of aden osine or ATP on the termination pattern of antidromic tachycardia in 1 7 patients (10 men, 7 women; mean age [+/-SD] 32 +/- 11 years) with on e or more accessory pathways. Adenosine (6 to 12 mg [n = 10]) or ATP ( 8 to 20 mg [n = 7]) was injected rapidly through a central venous line and followed by 10 ml of saline flush after induction of sustained an tidromic tachycardia. Results. Tachycardia was terminated in <2 min in 14 patients (82%) after the injection and remained unchanged in 3 (18 %). Tachycardia termination was due to conduction block in the accesso ry pathway (anterograde limb) in seven patients (50%) and in the AV no de (retrograde limb) in another seven, Adenosine or ATP caused accesso ry pathway block in seven (88%) of the eight patients lacking retrogra de accessory pathway conduction and in none of the nine patients havin g retrograde accessory pathway conduction (p < 0.01). All five patient s with an atriofascicular accessory pathway and unidirectional anterog rade conduction had tachycardia termination due to anterograde accesso ry pathway block after injection of adenosine or ATP. Conclusions. 1) Adenosine or ATP effectively terminates antidromic tachycardia; 2) the termination is related to block in either the accessory pathway or th e AV node; 3) accessory pathway block occurs in patients with a unidir ectional, anterogradely conducting accessory pathway, especially an at riofascicular accessory pathway.