Carotid sinus hypersensitivity: disease state or clinical sign of ageing? Insights from a controlled study of autonomic function in symptomatic and asymptomatic subjects

This study sought to improve the currently limited understanding of the pathophysiology of carotid sinus hypersensitivity (CSH) by comparing autonomic function measured by heart rate variability (HRV) and baroreflex sensitivity inpatients with symptomatic CSH and asymptomatic individuals with and without CSH. Twenty-two patients with symptomatic CSH, 18 individuals with asymptomatic CSH, and 14 asymptomatic older individuals without CSH were recruited to our study. Non-invasive measurements of heart rate and blood pressure were obtained during 10 min of supine rest. Low frequency (LF), high frequency (HF), and total power spectral density (PSD) for HRV were determined using the autoregressive method. The baroreflex slope (BRS) and baroreflex effectiveness index (BEI) were determined using the sequence method for baroreflex sensitivity. There were significant increases in the LF-HRV (P = 0.014), total PSD (P = 0.031), LF:HF (P = 0.047), normalized (nu) LF-HRV (0.049), down ramp BEI (P = 0.017), and total BEI (P = 0.038) in the symptomatic CSH group compared with non-CSH controls. The asymptomatic CSH group had significantly higher LF-HRV (P = 0.001), total PSD (P = 0.002), nuLF-HRV (P = 0.026), and LF:HF (P = 0.030), as well as up, down, and total BRS (P = 0.012, P = 0.015, and P = 0.011, respectively) and BEI (P = 0.049, P = 0.001, and P = 0.006, respectively) than non-CSH control participants. This study has demonstrated an association between CSH with increased resting sympathetic activity and baroreflex sensitivity regardless of the presence of symptoms, indicating the presence of autonomic dysregulation in individuals with CSH. Our findings therefore suggest that CSH is part of a generalized autonomic disorder but do not differentiate between asymptomatic and symptomatic individuals.