Noninvasive diagnosis in patients with undocumented tachycardias: Value ofthe adenosine test to predict AV nodal reentrant tachycardia

Introduction: Patients with symptoms suggestive of paroxysmal supraventricu lar tachycardia (PSVT) but no tachycardia documentation often undergo diagn ostic electrophysiologic study. In dual AV node physiology with AV node ree ntrant tachycardia (AVNRT), the anterograde fast pathway is more sensitive than the slow pathway to the effects of adenosine, The purpose of the study was to test the hypothesis that adenosine can be used as a bedside test fo r the diagnosis of dual AV node physiology and hence for AVNRT, Methods and Results: During electrophysiologic study, 37 patients without p rior documentation but symptoms indicative for PSVT received incremental do sages of adenosine during sinus rhythm until second-degree or greater AV bl ock was observed. Suggestive signs of dual AV node physiology on the surfac e ECG (sudden jump of PQ interval greater than or equal to 50 msec) were fo und in 13 (76%) of 17 patients with inducible AVNRT but in only 1 (5%) of t he remaining patients (P < 0.01), In the AVNRT group, the maximal increase of the PQ interval between two beats was greater (88 +/- 45 msec) than in t he remaining 20 patients (17 +/- 11 msec) (P < 0.01). Conclusion: Careful evaluation of surface ECG during administration of aden osine helps to identify patients prone to AVNRT, The adenosine test is a va luable noninvasive adjunct in patients with undocumented palpitations sugge stive of PSVT.