Tilt testing or implantable cardiac monitoring in the diagnosis of unexplained syncope

After initial evaluation, many older syncope patients do not receive a diagnosis. Both head-up tilt tests (HUTT) and implanted cardiac monitors (ICM) are recommended, but there is no consensus about which should be done first. The study objective was to assess whether first conducting a HUTT vs ICM provided a higher, earlier diagnostic yield. This single-center, retrospective analysis study included patients with undiagnosed syncope and age ≥ 5o years after clinical and ECG evaluation. Exclusion criteria included ECG conduction abnormalities and structural heart disease with left ventricular ejection fraction < 50%. The primary outcome was an etiologic diagnosis of syncope within 1 year; secondary outcomes included time to diagnosis and the proportion with a syncope diagnosis at the end of follow-up. There were 233 patients (135 males), mean age 69 ± 10 years, with a median 3 historical syncopes. Baseline characteristics were similar except the ICM group had more mild cardiomyopathies, injuries, and beta-blockers and diuretic therapies. After one year, there were more diagnostic outcomes in the HUTT (65/104, 63%) than in the ICM (37/129, 29%) group (p < 0.00001). There were more diagnostic outcomes in the HUTT group by study completion (69/104 vs 58/129, p = 0.0015). The median times to a syncope diagnosis were 1 day in the HUTT group and 97 days in the ICM group (hazard ratio 3.88, CI 2.66, 5.67; p < 0.001). In older patients with syncope of unknown etiology, first conducting a HUTT provided an earlier and higher diagnostic yield than first implanting an ICM.