Objectives: We sought to evaluate epidemiology, clinical features, and outcomes of patients with syncope and an abnormal response to adenosine triphosphate (ATP).
Background: Syncope remains of unknown origin in almost 30% of the patients. Injection of ATP induces in some of these patients, but not in control patients, a ventricular pause > or =6 s.
Methods: Patients with syncope of unknown origin had an intravenous injection of 20 mg of ATP. All patients had a tilt test.
Results: Among 214 patients, 19 (8.9%) had a positive ATP test result. The proportion of positive test results was higher (p < 0.002) in women (14.3%) than in men (2.2%). Ten patients (4.7%) had positive ATP and tilt test results. These patients (exclusively women) were older (p < 0.05) at the time of their fist syncope than the 67 patients with a negative ATP test result but a positive tilt test result. There was a trend for these two test results to be correlated (p = 0.07). Side effects were of short duration and benign. The mean duration of pauses was longer in women (p = 0.009). During a mean period of 31 +/- 14 months, recurrences of syncope were reported in 25% of patients.
Conclusions: The ATP test is a safe test with an "abnormal" result in <10% of patients with syncope of unknown origin. The profile of these patients is characteristic.