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Unexplained syncope in aging patients: Diagnostic performance of Tilt Table Tests and Implantable Cardiac Monitors
Professor Robert S Sheldon MD PhD, Roopinder Sandhu MD MSc, Dr Satish R Raj MD MSCI
Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Canada
Syncope in aging patients is common, leads to admissions to emergency departments and hospitals, triggers expensive investigations, and has a persistently high inability to establish a diagnosis. Partly this is due to uncertainty about how to proceed with investigation.
There are two competing diagnostic techniques; implantable cardiac monitors (ICMs) and headup tilt tests (HUT), and international guidelines are silent about which to perform first. Two early randomized studies reported the diagnostic yield of an early ICM strategy compared to conventional testing. RAST and EASYAS2 were conducted 15-25 years ago and used technology no longer current, and neither one randomized patients to HUTs versus ICMs. RAST had a positive HUT rate of 8.6%, far below representative rates then or now. The English EASYAS2 study had a primary outcome based on ECG documentation and used a device no longer marketed.
Methods & Results
We examined the diagnostic outcome rates for syncope patients >50 years old in the Calgary Syncope Clinic for ICMs (n=98) since June 2006 and HUTs (n=29; Italian protocol) since August 2017. The two groups had the same mean age (69 years), sex distribution (40% women), and median number of faints in the previous year (one). The primary outcome of both tests was syncope or clinically reminiscent presyncope.
HUTs were positive in 62% (95% CI 44, 77%), and ICMs yielded a diagnosis in 29% of patients after one year and 35% after two years. The median times to a diagnosis by HUT and ICM were one day and 2.8 months, respectively. The patients were followed after diagnosis to assess safety and syncope recurrence in each strategy. Our preliminary data (see figure) suggest that syncope recurs in the HUT arm at the same rate that it occurs in the ICM arm. In this small and selected population, the recurrence rate following a negative HUT is very low.
These data suggest that the current understanding that early ICM compared to HUT provides more and earlier diagnoses may be incorrect.
A strategy of first performing a tilt test to diagnose the cause of syncope in older patients appears to provide an earlier, higher diagnostic rate implanting an ICM. A randomized controlled pragmatic pilot trial (POST 8) is underway.