Cardiac autonomic balance versus cardiac regulatory capacity

The concept of autonomic balance views autonomic states along a bipolar continuum from sympathetic (S) to parasympathetic (P) dominance, whereas regulatory capacity models emphasize overall autonomic flexibility as a marker of the capacity for regulation. These two concepts were evaluated for their utility in characterizing patterns of autonomic control. Measures of P (high frequency heart rate variability, HF) and S (preejection period, PEP) cardiac control were obtained. A measure of cardiac autonomic balance (CAB) was derived as the difference in the normalized P index minus the S index, and a measure of cardiac autonomic regulation (CAR) was derived as the normalized P index plus the S index. Results reveal that CAR, but not CAB, was a significant predictor of the prior occurrence of a myocardial infarction, net of demographic and other variables, whereas CAB, but not CAR, was a significant predictor of concurrent diabetes.