Involvement of carotid baroreceptor function in blood pressure control in the chronic phase: Effect on 24-hour ambulatory blood pressure

Background. It is generally thought that the sole function of baroreceptors is for the regulation of rapid blood pressure fluctuations caused by postural changes and other motion. However, recent studies have suggested that baroreceptors may also be involved in blood pressure control in the chronic phase. Purpose. The study was performed to examine the involvement of carotid baroreceptors in blood pressure control in the chronic phase, through determination of the relationship between 24-hour blood pressure data and carotid baroreceptor function. Methods. Ambulatory blood pressure, ECG, and the number of steps during exercise were measured every 15 minutes with an ambulatory blood pressure monitor and a 24-hour Holter ECG fitted with an accelerometer (Cardy-II-p, Suzuken KK, Japan). In addition, the dependence of blood pressure on autonomic nerve activity and exercise was analyzed based on the frequency of the RR interval. Patients were divided into three groups based on different blood-pressure types: autonomic nerve-dependent, exercise-dependent, and independent types. Carotid baroreceptor function was evaluated using the sequence method; subjects adopted a supine position on a tilt table and their arterial pressure was monitored continuously using a Finapress finger cuff (Finapress, Ohmeda, Louisville, Colorado, USA). The study was performed in 90 patients, including 42 with essential hypertension whose blood pressure was well controlled. Results and Conclusions. A significant negative correlation was found between the mean 24-hour blood pressure and baroreceptor function for both systolic and diastolic pressure. Systolic pressure in patients of the independent type was significantly higher than that in patients of the exercise-dependent type. Furthermore, non-dipper hypertension was noted more frequently and baroreceptor function was significantly lower in independent-type patients, compared with autonomic nerve-dependent and exercise-dependent types, suggesting that independent-type blood pressure may be due to baroreceptor dysfunction. In conclusion, our results suggest that baroreceptor function might be involved in blood pressure control in the chronic phase, and baroreceptor dysfunction may contribute to the development of essential hypertension.