Based on data derived from our pilot study, approximately 60% of patients with ischemic cardiomyopathy indicated for ICD/CRT-D implant for primary prevention of sudden cardiac death have undiagnosed moderate or severe sleep apnea. Therefore, we expect the following distribution of patients among patients' groups: Group 1: n=400 patients; Group 2: n=200 patients; Group 3: n=200, Group 4: n=100 patients.