Simplified "ATP test" for noninvasive diagnosis of dual AV nodal physiology and assessment of results of slow pathway ablation in patients with AV nodal reentrant tachycardia

Diagnostic ATP Test for AVNRT. Introduction: We recently reported that admi nistration of adenosine triphosphate (ATP) during sinus rhythm identifies d ual AV nodal physiology (DAVNP) in 76% of patients with inducible sustained AV nodal reentrant tachycardia (AVNRT) at electrophysiologic (EP) study. I n that report, however, the ATP test was considered positive for DAVNP only when the results were reproducible at a given dose of ATP, The aim of the present study was to assess the value of a simplified ATP test for noninvas ive diagnosis of DAVNP and abolition or modification of the slow pathway (S P) after radiofrequency ablation (RFA) in patients with inducible sustained AVNRT. Methods and Results: The value of a single dose of ATP was studied in 105 p atients with inducible sustained AVNRT and in 31 control patients before pl acement of EP catheters in the cardiac chambers. ATP (10 to 60 mg, in 10-mg increments) was injected during sinus rhythm until ECG signs of DAVNP (gre ater than or equal to 50 msec increase or decrease in PR interval in two co nsecutive beats, or occurrence of greater than or equal to 1 AV nodal echo beat) or greater than or equal to second-degree AV block was observed. DAVN P was observed in only 1 (3.2 %) control patient. The test could be complet ed in 96 study patients. DAVNP was found by ATP test in 72 (75%) patients, whereas it was diagnosed by EP criteria in 82 (85%) patients, DAVNP by ATP test disappeared in 27 (96%) of 28 patients who underwent SP abolition and in 18 (60%) of 30 patients who underwent SP modification. In the 12 patient s with persistent DAVNP determined by ATP test after SP modification, the n umber of beats conducted over the SP was significantly reduced (from 6.3 +/ - 3.3 to 2.5 +/- 2.2 beats; P = 0.002). Conclusion: A single administration of ATP during sinus rhythm (at a given dose) enables noninvasive diagnosis of DAVNP in a high percentage of patien ts with inducible AVNRT and reliably confirms the results of RFA of the SP.