Reproducibility of head-up tilt testing potentiated with sublingual nitroglycerin in patients with unexplained...

Head-up tilt testing (HUTT) potentiated with sublingual nitroglycerin has gained acceptance as means of diagnosing neurally mediated syncope. To evaluate the reproducibility of HUTT potentiated with sublingual nitroglycerin, 48 patients with unexplained syncope prospectively underwent 2 consecutive tests 1 to 28 days apart. The initial test ended in syncope in 34 patients (71%). In 9 patients (19%) the test was positive during the drug-free phase, whereas 25 patients (52%) had syncope after nitroglycerin administration. Of these 34 patients with an initial positive test result, 27 (79%) had a reproducible outcome on repeat testing. Of 12 patients (25%) with an initial negative test result, 10 (83%) had a reproducible outcome on repeat testing. Of 2 patients (4%) with a first test ending in exaggerated response, both had a negative repeat test response. The overall reproducibility of sublingual nitroglycerin tilt-table testing was 77%. In a group of 23 patients with both positive tests, 19 (83%) had the same response modality (2 vasodepressor, 4 cardioinhibitory, 13 mixed response). In the same group of patients, individual trough heart rates correlated well with each other between tests. Finally, in the 27 patients with both positive tests, intrapatient time of onset of symptoms did not significantly correlate between tests. Thus, in patients with syncope of unknown origin, HUTT potentiated with sublingual nitroglycerin provides an adequate reproducibility when repeated on different days.