Coexistance of Carotid Sinus Hypersensitivity and Orthostatic Hypotension in Patients with Unexplained Syncope

BACKGROUND: Carotid sinus hypersensitivity (CSH) and orthostatic hypotension (OH) are established causes of syncope but are often considered separate entities. However, evidence suggests that CSH and OH may coexist and jointly contribute to syncope. This study investigates the relationship between CSH and OH in patients with unexplained syncope. METHODS: A total of 1,908 patients aged ≥40 years (age, 63.7 ± 13.0 years; men, 45.3%) with unexplained syncope underwent carotid sinus massage (CSM) and head-up tilt testing (HUT). Occurrence of CSH in classical and delayed OH, including asystolic CSM responses was analysed. RESULTS: Six-hundred-and-eighteen patients (32.4%, 68.9 ± 11.3 years) had OH, while CSH was present in 320 patients (16.8%, 72.2 ± 9.9 years), and was more common in patients with OH than without OH (24.1% vs. 13.3%, p < 0.001). Among patients with CSH, 46.6% also had OH. CSH occurred equally in both classical OH (62/275, 22.5%) and delayed OH (87/345, 25.2%). Among OH patients, CSH was associated with older age, male sex, lower supine diastolic blood pressure, hypertension, and syncope-related hospital admission. An asystolic CSM response was observed more often in OH patients (n = 42; 6.8%) compared with non-OH patients (n = 44, 3.4%, p < 0.001) and was associated with older age and lower resting heart rate. CONCLUSIONS: CSH and OH frequently coexist in adults over 40 years evaluated for syncope. CSM may reveal a clinically relevant cardioinhibitory reflex in a subgroup of OH patients, supporting comprehensive cardiovascular autonomic testing in unexplained syncope.