The Predictive Value of Heart Rate Variability for Long-Term Outcomes in Patients Undergoing Coronary Artery Bypass Grafting and ICU Referrals.

Background: Heart rate variability (HRV) is known to play a significant role in predicting poor prognosis after acute myocardial infarction. Nonetheless, its potential for predicting long-term adverse outcomes following revascularization procedures remains unclear. This study aims to elucidate this relationship. Methods: This prospective cohort study included 258 consecutive patients undergoing elective isolated coronary artery bypass grafting (CABG). All patients required ICU referral before hospital discharge. A 3-week cardiac rehabilitation program with 24-hour ECG Holter monitoring was planned for all patients. HRV was analyzed by computer and manually over-read. During a follow-up period ranging from 1 to 3 years, patients were contacted via phone to assess long-term outcomes, including death and major adverse cardiovascular events (MACE), such as myocardial infarction, reoperation, or brain stroke. Results: Out of 258 patients (177 males and 81 females) with an average age of 58.80±9.60 years, 4.3% of patients died due to cardiovascular events, and 15.1% experienced long-term MACE. A comparison of HRV indicators between the non-surviving and surviving subgroups revealed significantly lower mean RR, mean standard deviation of normal-to-normal HRV interval (SDNN), and low and high-frequency values in the former group. However, when comparing HRV indicators between the subgroups with and without long-term MACE, no significant differences were observed. Cox proportional hazard analysis demonstrated that decreased HRV (SDNN) effectively predicted long-term mortality in patients who underwent CABG. Conclusion: Lower postoperative HRV serves as a valuable predictor of long-term mortality after CABG in ICU patients, with reduced SDNN values particularly relevant for anticipating long-term adverse events.