The value of heart rate variability in predicting longterm poorer outcome in patients undergoing coronary artery bypasses grafting and referring intensive care unit

Abstract

Background
Heart rate variability (HRV) plays an important role in predicting poor prognosis after acute myocardial infarction, but whether this parameter is able to predict long-term adverse outcomes following revascularization procedures is still not clear. We investigated the value of HRV in predicting post- procedural adverse outcome (mortality and major adverse cardiovascular event or MACE) in patients undergoing coronary artery bypass grafting (CABG) surgery and referred to intensive care unit.

Methods

This prospective cohort study was performed on 258 consecutive patients underwent elective isolated CABG. All patients required intensive care unit referring before discharge from the hospital. All patients were planned for a 3-week cardiac rehabilitation program with a 24-hour electrocardiogram Holter monitoring. HRV was analyzed by computer and over-read manually. Within a follow-up period ranged 1 to 3 years, the patients were asked by phone for long-term outcome including death and MACE (including myocardial infarction, reoperation, or brain stroke).

Results

overall, 4.3% of patients died due to cardiovascular events and 15.1% suffered from long-term MACE. Comparing HRV indicators between non-survived and survived subgroups showed significantly lower mean RR, lower mean SDNN, lower LF and lower HF in former group. However, the comparison of HRV between the subgroups with and without long-term MACE showed no difference in HRV indicators between the two groups. Using Cox proportional hazard analysis, lowering HRV (SDNN) could effectively predict long-term death in patients underwent CABG.

Conclusion
Lower postoperative HRV can effectively predict long-term death after CABG in patients admitted to intensive care unit.