OBJECTIVE To study dynamics of 24-hour heart rate variability (HRV) after coronary artery bypass grafting (CABG) and to elucidate relationship between HRV dynamics and clinical course of the disease. METHODS A novel methodological approach to evaluation of HRV based on measurement of mean weighted rhythmogram variation (MWRV) was implemented. Ninety patients were studied before CABG. Then HRV was assessed in 2 weeks (61 patients), 2 (45 patients), 6 (24 patients)and 12 (33 patients) months after surgery. RESULTS At all study points HRV was lower in CHD patients than in healthy persons. Substantial lowering of average MWRV 2 weeks after surgery was followed by return to preoperative level by the end of 2 months, leveling off until 6 months and some decline by the end of a year. Individual changes of MWRV were assessed in 29 patients in whom HRV was evaluated at 5 or 4 study points. Three types of MWRV changes were distinguished: type 1 - "normal" dynamics (9 patients) - elevation of MWRV 2, 6 and 12 months; type 2 (10 patients) - elevation of MWRV after 2 and 6 months with subsequent lowering by the end of 1 year; type 3 (10 patients) - lowering of MWRV In 2 and/or 6 months. The following relationships between MWRV changes and clinical course after surgery were observed: there were no complications among patients with type 1 MWRV dynamics; 8 of 10 type 2 patients had signs of heart failure, or blood pressure elevation, or recurrence of angina by the end of 1 year: among 10 type 3 patients 6 experienced various complications. Recurrence of angina at various intervals after CABG occurred in 5 patients and in all it was associated with MWRV decrease. CONCLUSIONS Pronounced decrease of MWRV between 2 and 12 months after CABG is associated with worse clinical course and its detection should trigger additional investigation and care of a patient.