ABNORMAL BAROREFLEX CONTROL OF HEART-RATE IN DECOMPENSATED CONGESTIVE-HEART-FAILURE AND REVERSAL AFTER COMPENSATION

Congestive heart failure (CHF) causes impairment of baroreflex control of heart rate (HR). To determine if this derangement is reversible, the cardiac chronotropic control was assessed in 10 patients with class IV chronic CHF of various etiologies before and after compensation achieved by bed rest, salt restriction, diuretics and vasodilators. Mean time between the 2 studies was 15 +/- 3 days. The management was modified 3 days before the second autonomic evaluation, so as to reestablish the same diet and pharmacologic conditions of the previous study. Compensation led to significant reduction in symptom-based class, body weight, and pulmonary and systemic congestion. Mean +/- standard error of the mean HR responses (beats/min) before and after compensation were, respectively: (1) to atropine (0.04 mg/kg): 10 +/- 2 and 27 +/- 2 (p < 0.01); (2) to handgrip (30% maximum capacity, 1 minute): 9 +/- 2 and 19 +/- 3 (p < 0.005); (3) to head-up tilt (5 minutes): 4 +/- 3 and 20 +/- 4 (p < 0.005). Mean +/- standard error of the mean baroreflex sensitivity (ms/mm Hg) of RR responses to phenylephrine and amyl nitrate-induced changes in systolic pressure was, respectively, in each condition: phenylephrine, 0.9 +/- 0.2 and 8 +/- 2.3 (p < 0.05); amyl nitrate, 0.3 +/- 0.2 and 4.1 +/- 1.1 (p < 0.05). A significant correlation between improvement in HR responses to atropine and tilt and changes in body weight was obtained. These findings show a reversible component of impaired baroreflex control of HR in severe CHF, possibly due to its congestive effects.