Reduced baroreflex sensitivity in situational syncope compared with vasovagal syncope: Evidence for different baroreflex profile

BACKGROUND: Baroreflex sensitivity (BRS) reflects short-term cardiovascular autonomic regulation and contributes to blood pressure stability, a key determinant of cerebral perfusion. We aimed to assess BRS in patients with situational syncope (SS) and to compare it with that of patients with vasovagal syncope (VVS) under standardized conditions. METHODS AND RESULTS: We prospectively evaluated consecutive patients with suspected reflex syncope. Patients with confirmed SS or VVS and available BRS assessment at rest and during early orthostatic phase were included. The nearest neighbor propensity score matching (PSM) method with a 1:1 ratio was applied to balance baseline characteristics. Among 182 patients, 45 with SS were matched to 45 with VVS. Compared with VVS, SS patients exhibited significantly lower BRS both in the supine position (5.8±2.5 vs 7.4±4.0 ms/mmHg; p=0.02) and during orthostatic stress (5.3±2.7 vs 6.8±3.4 ms/mmHg; p=0.02). No differences in BRS were observed across different situational triggers. CONCLUSIONS: Situational syncope is associated with reduced baroreflex sensitivity compared with vasovagal syncope, supporting the presence of distinct baroreflex profiles within reflex syncope. These findings may have implications for pathophysiological classification and personalized management strategies.