CARDIAC AUTONOMIC CONTROL IS INVERSELY RELATED TO BLOOD-PRESSURE VARIABILITY RESPONSES TO PSYCHOLOGICAL CHALLENGE

Blood pressure exhibits variability (BPV) at low (0.02- to 0.07-Hz), m id (0.07- to 0.15-Hz)-, and high (0.15- to 0.50-Hz) frequencies. Evide nce suggests that BPV responses to challenge are inversely related to cardiac autonomic control. We tested this hypothesis by examining the BPV responses to psychological stressors in 22 normal subjects who dif fered in cardiac control, operationalized as resting heart period vari ability (HPV). HPV and BPV were measured noninvasively on a beat-to-be at basis. The stressors produced a significant increase in heart rate and a small but significant increase in diastolic blood pressure. As p redicted, the changes in BPV in response to the stressors were inverse ly related to resting HPV. The results are interpreted in terms of a m odel of cardiovascular control that holds that BPV originates from fee dforward effects of central control of the heart, feedback effects med iated through the baroreflexes, and direct sympathetic vascular effect s.