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Heart rate variability after coronary artery bypass graft surgery: a prospective 3-year follow-up study
Seref Demirel1, Vakur Akkaya, Hüseyin Oflaz
1Department of Internal Medicine, University of Istanbul, Turkey.
Insights
Heart rate variability (HRV) significantly drops after coronary artery bypass grafting (CABG) surgery but largely recovers within three months. This early HRV impairment is linked to acute surgical effects, with full recovery observed over time.
Area of Science:
- Cardiology
- Autonomic Nervous System Function
- Cardiac Surgery
Background:
- Autonomic heart rate control is known to be impaired following Coronary Artery Bypass Grafting (CABG).
- Understanding the temporal dynamics of Heart Rate Variability (HRV) changes post-CABG is crucial for patient recovery assessment.
Purpose of the Study:
- To investigate the temporal pattern of Heart Rate Variability (HRV) changes after Coronary Artery Bypass Grafting (CABG).
- To determine the recovery timeline of autonomic heart rate control post-CABG.
Main Methods:
- Prospective study involving 12 patients with coronary artery disease undergoing CABG.
- 24-hour Holter recordings were obtained pre-CABG and at 1 week, 3 months, 6 months, 1 year, and 3 years post-CABG.
- Analysis included time-domain and frequency-domain HRV parameters, and the LF/HF ratio.
Main Results:
- HRV parameters (time-domain and frequency-domain) decreased significantly immediately after CABG.
- Most HRV parameters recovered by 3 months post-CABG, with exceptions like mean NN, rMSSD, and pNN50.
- The LF/HF ratio initially decreased, returned to baseline by 3 months, and increased thereafter, with complete recovery by 3 years. No correlation was found between HRV changes and surgical factors like cross-clamping time or cardioplegia volume.
Conclusions:
- The acute decrease in HRV post-CABG is primarily attributed to the immediate surgical impact, independent of patient preoperative status or postoperative course.
- The eventual complete recovery of HRV suggests resolution of ischemia or beneficial effects of medications like ACE inhibitors.
Background:
Autonomic heart rate control is impaired after CABG. The aim of this study was to establish the temporal pattern of change in the decrease of HRV observed after CABG.
Methods And Results:
Twelve patients with coronary artery disease were assessed with 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, 6 months, 1 year, and 3 years after CABG. All the time-domain and frequency-domain HRV parameters decreased precipitately after CABG and were mostly recovered 3 months after CABG except mean NN, rMSSD, and pNN50. The ratio of LF to HF showed a slight decrease after surgery, recovered to preoperative values after 3 months, surpassed, and continued to increase 6 months after surgery. At 3 years of follow-up the recovery was complete. The rate of change of time-domain and frequency-domain parameters were calculated and their correlation with aortic cross-clamping time, number of vessels bypassed, the amount of cardioplegic used were sought and no statistically significant correlation was found.
Conclusion:
The recovery of HRV regardless to the preoperative state of the patients and their postoperative course implies that the early drop of HRV after CABG was related to the acute effects of surgery. Late complete recovery of HRV may be due to resolution of ischemia or use of angiotensin-converting enzyme inhibitor.