We prospectively correlated the results of tilt testing (TT) and
adenosine triphosphate test (
ATP) with the findings observed during a spontaneous syncopal relapse by means of an implantable loop recorder (ILR) in patients with a clinical diagnosis of neurally mediated
syncope.
METHODS AND RESULTS: We included patients with three or more clinically severe
syncopal episodes in the last 2 years without significant electrocardiographic and cardiac abnormalities. Patients with
orthostatic hypotension and
carotid sinus syncope were excluded. After ILR implantation, patients were followed until the first documented
syncope. Among 392 enrolled patients, 343 underwent TT, which was positive in 164 (48%), and 180
ATP test, which was positive in 53 (29%).
Syncope was documented by ILR in 106 (26%) patients after a median of 3 months. Patients with positive and negative TT had similar baseline characteristics, syncopal recurrence rate, and mechanism of
syncope, but those with positive TT had more frequently no or slight rhythm variations during spontaneous
syncope (45 vs. 21%, P=0.02). An asystolic pause was more frequently found during spontaneous
syncope than during TT (45 vs. 21%, P=0.02), but there was a trend for those with an asystolic response during TT also to have an asystolic response during spontaneous
syncope (75 vs. 37%, P=0.1). Patients with positive
ATP test responses showed syncopal recurrence rates and mechanism of
syncope similar to those with negative
ATP tests.
CONCLUSION: In patients with neurally mediated
syncope, clinical characteristics, outcome, and mechanism of
syncope are poorly correlated and not predicted by the results of TT and
ATP test. Therefore, these tests are of little or no value in guiding specific
therapy.