Time domain measurement of the vascular and myocardial branches of the baroreflex: A study in physically active versus sedentary individuals.

This study tests the spontaneous sequence method for the evaluation of the cardiac, vasomotor, and myocardial branches of the baroreflex. Systolic blood pressure (SBP), interbeat interval (IBI), stroke volume (SV), preejection period (PEP), and total peripheral resistance (TPR) were continuously recorded in 33 physically active and 25 sedentary participants at rest and during a mental arithmetic task. Sequences of spontaneous covariation between SBP and IBI (for the cardiac branch), SV and PEP (for the myocardial branch), and TPR (for the vasomotor branch) were located. The slope of the regression line between values in the sequences produced an estimate of baroreflex sensitivity (BRS), and the proportion of progressive SBP changes that elicited reflex modulations yielded an estimate of baroreflex effectiveness (BEI). The active group showed greater BRS in all three branches than the sedentary group. Cardiac and vasomotor BEI decreased during the arithmetic task in the sedentary group but not in the active one. Only cardiac BRS decreased during the arithmetic task. In conclusion, the method appears appropriate for the simultaneous assessment of the three baroreflex branches. The assessment of the vascular branch of the baroreflex may have prognostic relevance in the development of hypertension or other cardiometabolic diseases.