Etiology and Outcomes of Syncope in Patients With Structural Heart Disease and Negative Electrophysiology Study

Objectives: This study sought to determine the cause of recurrent syncope and clinical outcomes by using the head-up tilt test (HUTT) and an insertable loop recorder (ILR) in patients with structural heart disease (SHD) and negative electrophysiology study (EPS) results. Background: Patients with syncope and SHD with negative EPS findings have a low risk of sudden cardiac arrest. Nevertheless, the cause of recurrent syncope and the outcomes in these patients are not well characterized. Methods: This prospective study evaluated syncope patients with SHD and negative EPS results by using HUTT (with sublingual nitroglycerine [NTG] provocation as needed) and ILR. A total of 41 SHD patients (27 patients [66%] had coronary arterial disease, and 14 patients [34.15%] had dilated cardiomyopathy with mean EF of 42 ± 4.8% [range 30% to 49%]) were included. Results: HUTT findings were positive in 25 patients (61%) in group A and negative in 16 patients (39%) in group B. An ILR was implanted in 21 of 25 group A patients (84%) and in 12 of 16 group B patients (75%), and they were followed for 15 ± 8 months. During follow-up, 17 of 21 patients (81%) in group A and 5 of 12 patients (41.7%) in group B had ILR evidence consistent with reflex syncope. One group B patient had documented atrioventricular block and underwent pacemaker implantation. There were no malignant ventricular arrhythmias or deaths on follow-up. Conclusions: Reflex syncope is the most common cause of syncope and accounts for approximately 60% of cases in patients with SHD, negative EPS results, left ventricular systolic dysfunction with left ventricular EF >30%, and not in heart failure.