Baroreflex sensitivity

Baroreflex sensitivity (BRS) quantifies the magnitude of the heart rate response to acute changes in arterial blood pressure, expressed as milliseconds of RR-interval change per mmHg of pressure change. Arterial baroreceptors in the carotid sinus and aortic arch tonically modulate vagal and sympathetic outflow to buffer blood pressure fluctuations; a higher BRS indicates a more responsive and efficient reflex arc. BRS declines with age, hypertension, heart failure, and diabetes, and low BRS is an independent predictor of adverse cardiac events and mortality, particularly post-myocardial infarction. It is assessed by pharmacological methods (phenylephrine or nitroprusside bolus), spontaneous sequence analysis, or the modified Oxford technique, and is studied as a cardiovascular aging biomarker responsive to exercise training and weight loss.