Sleep apnoea in patients with heart failure. Part I: diagnosis, definitions, prevalence, pathophysiology and haemodynamic consequences.

Sleep disorder specialists manage 90% of patients suffering from obstructive sleep apnoea, which affects 10% of the general population. From another perspective, cardiovascular disease specialists are particularly challenged by sleep apnoea, since it affects a large proportion of their patients and its complications are largely cardiovascular. At least 50% of patients with chronic heart failure (HF) suffer from sleep apnoea, predominantly central and/or Cheyne-Stokes respiration as opposed to obstructive sleep apnoea. While its effect on survival remains uncertain, sleep apnoea promotes the progression of chronic HF and is a predictor of poor prognosis. After screening by cardiologists, patients presenting with chronic HF and sleep apnoea should be referred to a sleep disorder specialist for diagnostic confirmation and treatment. In Part I of this review, we describe the diagnostic steps recommended when sleep apnoea is suspected in patients with chronic HF. We also review the definitions of abnormal sleep-related respiratory events and the prevalence, pathophysiology and haemodynamic consequences of sleep apnoea in this patient population.