Short term effect of adaptive servo-ventilation on muscle sympathetic nerve activity in patients with heart failure.

Chronic heart failure (HF) is characterized by sympathetic overactivation and periodic breathing. We examined whether adaptive servo-ventilation (ASV) exerts a sympathoinhibitory effect in patients with HF via normalizing respiratory pattern. Muscle sympathetic nerve activity (MSNA), heart rate, blood pressure, respiratory pattern and oxygen saturation were examined in 29 HF patients without obstructive sleep apnea (age, 61±15years; ejection fraction, 0.32±0.09; obstructive apnea index, <5/h) before (10 min), during (30 min) and after (10 min) the application of ASV. Periodic breathing was defined as a repeated oscillation of tidal volume with regularly recurring hyperpnea and hypopnea with a variation in tidal volume of greater than 25%. The severity of respiratory instability was determined using the coefficient of variation of tidal volume (CV-TV). Of 29 patients with HF, 11 had periodic breathing and 18 did not. There was a modest positive correlation between MSNA and CV-TV (n=29, p<0.05). ASV reduced respiratory rate, CV-TV and MSNA only in the group with periodic breathing (p<0.01). Change in MSNA significantly correlated with changes in respiratory rate, CV-TV and presence of periodic breathing. However, multivariate analyses revealed that respiratory rate and CV-TV were independent predictors of change in MSNA. ASV reduces MSNA by slowing respiratory rates and stabilizing respiratory patterns in patients with HF.