To investigate the impact of obstructive sleep apnoea (OSA) on circadian profile of cardiac arrhythmia in patients with ischemic heart disease (IHD) and to determine clinical markers of OSA.52 patients (31 males, 21 females, body mass index 30.5 +/- 5.8 kg/m2) with IHD admitted to hospital for ventricular extrasystole and paroxysmal cardiac fibrillation filled in questionnaires, were examined anthropometrically, with nocturnal cardiorespiration and holter monitoring. Cluster and correlation-regression mathematical analyses of the findings were made.OSA was detected in 42 (80.8%) patients. Patients with primarily nocturnal arrhythmia, compared to those with diurnal arrhythmia had a significantly higher index apnea/hypopnea (29.2 and 21.5 vs 4.4, respectively), more pronounced fall in saturation (12.9 and 9.4% vs 4.9%, respectively) and lower body mass index. In 12 (23%) patients arrhythmia arose in parallel with episodes of sleep apnea/hypopnea. Mathematical analysis determined the following clinical markers of sleep respiratory disorders: regular intensive nocturnal snoring, body mass index > 25 kg/m2 and diurnal drowsiness > 15 scores by Epworth scale.ORDS may provoke cardiac arrhythmia in patients with IHD.