Increased Baroreflex Sensitivity and Reduced Cardiovascular Reactivity in Individuals with Chronic Low Blood Pressure

This study investigated aberrations in baroreflex function and cardiovascular reactivity related to the condition of chronic low blood pressure. In 40 hypotensive and 40 normotensive control subjects, blood pressures were continuously recorded at rest and during mental stress. Baroreflex sensitivity was determined in the time domain using sequence analysis. Beat-to-beat hemodynamic indices were estimated from the blood pressure waveforms by means of Modelflow analysis. In the hypotensive sample, a higher baroreflex sensitivity was observed under both conditions. Furthermore, this group experienced a less pronounced increase of blood pressure and stroke volume under stress. The findings underline the involvement of the baroreflex in the long-term setting of tonic blood pressure and suggest its relevance in the etiology of chronic hypotension. In addition, this study documents reduced cardiovascular reactivity and thus deficient hemodynamic adjustment to situational requirements in chronic low blood pressure. (Hypertens Res 2008; 31: 1873-1878)