Study objective: Central sleep apnea (CSA) associated with Cheyne-Stokes respiration in patients with congestive heart failure (CHF) is thought to be an acquired pattern of respiratory control instability related, at least in part, to elevated sympathetic nervous system activity. The effect of restoring heart function to normal with heart transplantation in patients with CHF and CSA has only been reported within weeks of the transplant and with varying results. The purpose of the study was to evaluate the impact of successful heart transplant on sympathetic nervous system activity and CSA severity in patients with CHF.
Design: Controlled prospective trial.
Setting: University hospital.
Patients: Twenty-two patients with CHF (13 patients with CSA, and 9 patients with no sleep-disordered breathing [SDB]).
Interventions and measurements: Polysomnography, left ventricular ejection fraction (LVEF), and overnight urinary norepinephrine excretion (UNE) were measured before and > 6 months after successful heart transplantation.
Results: In the CSA group, there was a fall in apnea-hypopnea index (AHI) [mean +/- SD, 28 +/- 15 to 7 +/- 6/h; p < 0.001] and UNE (48.1 +/- 30.9 to 6.1 +/- 4.8 nmol/mmol creatinine, p < 0.001) associated with normalization of LVEF (19.2 +/- 9.3% to 53.7 +/- 6.1%, p < 0.001) at 13.2 +/- 8.3 months following heart transplantation. Of the CSA group following transplantation, seven patients had no SDB (AHI < 5/h), three patients had persistent CSA (AHI, 12.3 +/- 0.9/h) and four patients acquired obstructive sleep apnea (OSA) [AHI, 11.2 +/- 7.4/h]. In comparison, none of the control group acquired CSA or OSA after transplantation.
Conclusions: We conclude that CSA may persist despite normalization of heart function and sympathetic nerve activity.