Heart Rhythm. 2020 Dec 13:S1547-5271(20)31144-9. doi: 10.1016/j.hrthm.2020.12.009. Online ahead of print.
BACKGROUND: Syncope in patients with mid-range LVEF can be due to potentially serious arrhythmic causes. However, there is no clear consensus regarding the best way to manage these patients.
OBJECTIVES: Determine the causes of syncope and assess the diagnostic yield and safety of a stepwise work-up protocol in this population.
METHODS: Prospective observational study. A stepwise work-up protocol was applied to patients with LVEF 35-50% and unexplained syncope after initial assessment (Step 1).
RESULTS: 104 patients were included. (median age 75.6 years [IQR 67.6-81.2 years], median LVEF 45% [IQR 40-48%], median follow-up 2.0 years [IQR 0.7-3.3 years]). In 71 patients (68.3%) a diagnosis was reached, 55 (77,5%) in Step 2 (Hospital admission & electrophysiology study (EPS)) and 16 (36.5%) in Step 3 (implantable cardiac monitor (ICM)). Arrhythmic causes were the most common etiology (45.2% AV block, 9.6% VT). 60 (57.7%) patients required the implantation of a cardiac device, 11 with a defibrillation function. Patients diagnosed in Step 3 had a greater global risk of recurrence of syncope (HR 6.5; 95% CI 2.3-18.0). The mortality rate was 8.1% person-years and the sudden or unknown death rate was 0.9 % person-year.
CONCLUSIONS: In patients with mid-range LV dysfunction and syncope of unknown cause, a systematic diagnostic strategy based on EPS and/or ICM implantation allows a diagnosis to be reached in a high proportion of cases and guides the treatment. Arrhythmia is the most common cause of syncope in this population, particularly AV block.