Background: It is important to identify the clinical indicators of poor prognosis and treatable conditions that might contribute to the progression of heart failure (HF) and pulmonary hypertension (PH) in the group of patients with dilated cardiomyopathy (DCM) and concomitant obstructive sleep apnoea (OSA).

Aim: To evaluate the influence of OSA on echocardiographic and haemodynamic parameters in patients with DCM, and the outcome in long-term follow-up.

Methods: We enrolled patients with DCM and severely impaired ejection fraction (EF < 30%). Each patient underwent polygraphy, echocardiography, and right heart catheterisation. Subjects were divided into groups based on the apnoea–hy­popnoea index (AHI): > 0 and < 5 (group I), ≥ 5 and ≤ 15 (group II), > 15 and ≤ 30 (group III), and > 30 (group IV). We compared the OSA-free (AHI < 5) subjects with those with OSA (AHI ≥ 5). The evaluated clinical end-points were death and orthotropic heart transplant.

Results: The study population comprised 51 patients. Mean EF was 22%; 59% of patients were suffering from OSA. The increased severity of OSA correlated with worse pulmonary haemodynamics. Patients with OSA had higher mean pulmonary arterial pressure and pulmonary vascular resistance than individuals without OSA (p = 0.044, p = 0.032, respectively). The highest chamber diameters assessed in echocardiography were found in group IV (p < 0.05). A total of 10 end-points oc­curred during follow-up (8.9 ± 5.1 months), with significant differences observed between groups I–IV and the highest rate in group IV (p < 0.001).

Conclusions: The increasing severity of OSA worsens the prognosis of DCM patients, independently of severe HF and coex­istent PH. Systematic OSA screening in patients with HF might facilitate identification of individuals at high risk of progression of pulmonary haemodynamic impairment and end-point rate.