High prevalence and persistence of sleep apnoea in patients referred for acute left ventricular failure and medically treated over 2 months

Abstract

Aims. Cardiac failure patients were studied systematically using polysomnography 1 month after recovering from acute pulmonary oedema, and again after 2 months of optimal medical treatment for cardiac failure. Methods and Results. This prospective study of consecutive patients was conducted in a cardiac care unit of a university hospital. Vo2 measurements and left ventricular ejection fraction were recorded. Thirty-four patients, initially recruited with pulmonary oedema, improved after 1 month of medical treatment to NYHA II or III. They were aged less than 75 years and had a left ventricular ejection fraction less than 45% at the time of inclusion. Age was 62 (9) years, body mass index = 27 (5) kg.m-2 and an ejection fraction = 30 (10)%. Eighteen of the 34 patients (53%) had coronary artery disease. Twenty-eight of the 34 had sleep apnoea syndrome with an apnoea + hypopnoea index > 15.h-1 of sleep. Thus, the prevalence of sleep apnoea in this population was 82%. Twenty-one of 28 (75%) patients had central sleep apnoea and seven of 28 (25%) had obstructive sleep apnoea. Patients with central sleep apnoea had a lower Paco2 than those with obstructive sleep apnoea (33 (5) vs 37 (5) mmHg, P < 0.005). Significant correlations were found between apnoea + hypopnoea index and peak exercise oxygen consumption (r = -0.73, P < 0.01), and apnoea + hypopnoea index and Paco2 (r= -0.42, P = 0.03). When only central sleep apnoea patients were considered, a correlation between apnoea + hypopnoea index and left ventricular ejection fraction was also demonstrated (r = -0.46, P < 0.04). After 2 months of optimal medical treatment only two patients (both with central sleep apnoea) showed improvement (apnoea + hypopnoea index < 15.h-1). Conclusions. We have demonstrated a high prevalence of sleep apnoea, which persisted after 2 months of medical treatment, in patients referred for acute left ventricular failure. Central sleep apnoea can be considered a marker of the severity of congestive heart failure.