Treatment of Unexplained Syncope: A Multicenter, Randomized Trial of Cardiac Pacing Guided by Adenosine 5'-triphosphate Testing.
Author(s): Flammang D, Church TR, De Roy L, Blanc JJ, Leroy J, Mairesse GH, Otmani A, Graux PJ, Frank R, Purnode P
Affiliation(s): 1 Croix Rousse University Hospital, Lyon, France;
Publication date & source: 2011-11-15, Circulation., [Epub ahead of print]
BACKGROUND: The origin of 40% of syncope cases remains unknown even after a complete diagnostic work-up. Previous studies have suggested that adenosine 5'-triphosphate (ATP) testing has value in selecting successful therapy. This patient-blinded, multicenter, randomized superiority trial tested whether, in patients with syncope of unknown origin (SUO), selecting cardiac pacing in those with a positive ATP test results in fewer recurrences than those who do not receive pacing. METHODS AND RESULTS: From 2000 to 2005, 80 consenting patients (mean age 75.9 +/- 7.7 years, 81% women, and 56% without diagnosed structural heart disease) with SUO and atrioventricular or sinoatrial block lasting longer than 10 seconds (average 17.9 +/- 6.8 seconds) under ATP administration (20 mg IV bolus) were recruited from 10 hospitals, implanted with programmable pacemakers, and randomized to either active pacing (dual-chamber pacing at 70 beats per minute [bpm]) or backup pacing (atrial pacing at 30 bpm). Patients were followed regularly for up to five years for any syncope recurrence, the primary outcome. Mean follow-up was 16 months. Syncope recurred in eight (21%) of 39 patients randomized to active pacing and in 27 (66%) of 41 randomized to backup pacing (control), yielding a hazard ratio of 0.25 (95% CI: 0.12, 0.56). After recurrence, the 27 recurrent control patients were reprogrammed to active pacing and only one reported subsequent syncope. CONCLUSIONS: This study suggests that, in elderly patients with SUO and positive ATP tests, active dual-chamber pacing reduces syncope recurrence risk by 75% (95% CI 44% to 88%). CLINICAL TRIAL REGISTRATION INFORMATION: http://www.controlled-trials.com/ISRCTN00029383; Unique Identifier: ISRCTN00029383.