Variations in diagnostic yield of head-up tilt test and electrophysiology in groups of patients with syncope of unknown origin.

AIMS To assess the diagnostic yield of the head-up tilt test and electrophysiology in different groups of patients with syncope of unknown origin established according to simple clinical criteria. METHODS AND RESULTS Six hundred consecutive patients with syncope of unknown origin submitted to a tilt test. Two hundred and forty seven of them also underwent electrophysiology. Patients were divided into groups according to age at the time of first syncope, ECG findings and the presence of organic heart disease. Positive responses to the tilt test were more common in patients who had suffered their first syncope at an age equal to or below 65 years (group I) than in older patients (group II) (47% vs 33%, P<0.05, OR 1.8, CI 1.2-2.78), and in patients with a normal ECG and without organic heart disease than in the other subgroups of patients (47% vs 37%, P<0.008, OR 1.6). The lowest rate of positive response was observed in older patients with an abnormal ECG and organic heart disease. Electrophysiology disclosed abnormal findings in group II more often than in group I (23% vs 7%, P<0.001, OR 3.7, CI 1.7-9.2). The diagnostic yield from electrophysiology was higher in patients with an abnormal ECG than in those with a normal ECG (22% vs 3.7%, P<0.0005, OR 7.1), and it was especially low in patients with a normal ECG and without organic heart disease (2.6%). CONCLUSION The diagnostic yield of the tilt test and electrophysiology differs in groups of patients with syncope of unknown origin, established according to simple clinical criteria. These findings have a bearing on selecting the most appropriate test in a particular patient.