Background: Chemoreflex-mediated sympathetic activation contributes to both initiation and progression of chronic heart failure (CHF).
Method: To study the direct role of increased peripheral chemosensitivity in reducing sympathetic baroreflex function in CHF patients, we compared sympathetic baroreflex function, assessed by the slope of the relationship between muscle sympathetic nerve activity (MSNA) and DBP, in CHF patients with augmented (n = 18) and normal (n = 20) peripheral chemosensitivity. Using a double-blind, randomized, vehicle-controlled study, we examined the effect of chemoreflex deactivation (by breathing 100% oxygen for 15 min) on sympathetic baroreflex function in CHF patients with elevated and with normal chemosensitivity.
Results: Baseline MSNA was elevated (60.6 ± 3.2 vs. 48.9 ± 3.7 bursts/min, P < 0.05) and sympathetic baroreflex function impaired (3.06 ± 0.55 vs. 5.51 ± 0.69 % bursts/mmHg, P < 0.05) in CHF patients with augmented peripheral chemosensitivity compared with controls. Administration of 100% oxygen led to a significant decrease in MSNA (from 60.5 ± 3.2 to 52.6 ± 3.2 bursts/min, P < 0.001) and increase in sympathetic baroreflex (from 2.95 ± 0.56 to 6.18 ± 0.77, P < 0.001) in CHF patients with enhanced chemoreflex sensitivity. In contrast, neither room air nor 100% oxygen changed MSNA, hemodynamics or sympathetic baroreflex function in CHF patients with normal chemosensitivity.
Conclusion: We report for the first time that increased peripheral chemoreflex sensitivity directly decreases sympathetic baroreflex function in CHF patients. This interaction contributes to sympathetic overactivity and blunted sympathetic baroreflex function of CHF patients and may explain how chemoreceptors contribute to the bad prognosis of CHF patients.