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.