Impact of sleep disordered breathing severity on hemodynamics, autonomic balance and cardiopulmonary functional status in chronic heart failure.

BACKGROUND: Despite advances in medical therapy, sleep disordered breathing (SDB) remains highly prevalent in chronic heart failure (CHF). The impact of severity of SDB on sympathovagal balance, central hemodynamic responses and cardiopulmonary functional status in these patients is uncertain.

METHODS: Thirteen patients with stable CHF (mean age+/-10 years; 12 NYHA Class II, 1 Class III) identified with SDB (apnoea-hypopnoea index [AHI] >or=5) by polysomnography underwent echocardiography, standard hemodynamic and functional assessment, heart rate variability analysis and treadmill cardiopulmonary testing.

RESULTS: Mean AHI of study cohort was 32+/-19, with predominant hypopnoea. Anthropomorphic measurements of obesity correlated positively with increasing AHI severity (p<0.05). NYHA functional class, 6-minute walk distance, measures of left ventricular systolic and diastolic function, serum brain natriuretic peptide levels, cardiac output and VO(2)peak at baseline did not differ with SDB severity. Although SDB severity did not impact on VE/VCO(2)-slope, patients in the highest AHI tertile (AHI>35) demonstrated significantly greater respiratory effort (VE), despite similar VO(2)peak during exercise. Increasing SDB severity was associated with higher resting and post-exercise heart rates, reduced heart rate variability, and possibly slower post-exercise heart rate recovery, consistent with autonomic imbalance.

CONCLUSIONS: SDB severity was most closely associated with the degree of autonomic dysfunction, and abnormal ventilatory response during and post-exercise in a group of stable ambulant patients with similar severity of CHF on contemporary therapy.