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

Mohammad Javad  Mehrabanian; Mehdi Dehghani  Firoozabadi; Behrang  Nooralishahi; Afarin  Zamani; Naser  Kachoueian

doi:10.18502/jthc.v19i4.17611

Mohammad Javad Mehrabanian Department of Anesthesiology, School of Medicine, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran.
Mehdi Dehghani Firoozabadi Department of Anesthesiology, School of Medicine, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran.
Behrang Nooralishahi Department of Anesthesiology, School of Medicine, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran.
Afarin Zamani Department of Anesthesiology, School of Medicine, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran.
Naser Kachoueian Department of Cardiac Surgery, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

DOI: https://doi.org/10.18502/jthc.v19i4.17611

Keywords: Cardiac surgery; Heart rate variability; Coronary artery bypass grafting; Intensive care units; Prognosis; Mortality; Cardiac rehabilitation; Risk assessment

Abstract

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.