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Changes in ultra-low and very low frequency heart rate variability after coronary artery bypass grafting
1Department of Cardiovascular Surgery, Daini Hospital, Tokyo Women's Medical University, Japan. ysudaca@dnh.twmu.ac.jp
Insights
Coronary artery bypass grafting (CABG) impacts heart rate variability (HRV). While ULF/TF ratios improved post-CABG, indicating reduced ischemia, other HRV components suggest delayed cardiac autonomic recovery.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Medical Engineering
Background:
- Heart rate variability (HRV) reflects autonomic nervous system (ANS) function.
- Coronary artery bypass grafting (CABG) is a major cardiac surgery with potential ANS impact.
- Ultra-low (ULF) and very low (VLF) frequency components of HRV are sensitive indicators of cardiac health.
Purpose of the Study:
- To evaluate the effects of CABG on ULF and VLF components of HRV.
- To assess changes in various HRV spectral components and their ratios pre- and post-surgery.
- To understand the implications of these changes for cardiac autonomic function and myocardial ischemia.
Main Methods:
- Prospective study involving 49 CABG patients (38-77 years).
- 24-hour ambulatory electrocardiographic (AECG) monitoring preoperatively and 4 weeks post-CABG.
- Maximum entropy method analysis for HRV spectral components (ULF, VLF, LF, HF, TF).
Main Results:
- Significant increase in average 24-h heart rate post-CABG (69 to 82.9 bpm).
- Significant decrease in ULF, VLF, and LF power post-CABG.
- Significant increase in ULF/TF ratio (0.6496 to 0.7003) and decrease in VLF/TF and LF/TF ratios post-CABG.
Conclusions:
- CABG surgery leads to significant alterations in HRV spectral components.
- The increase in ULF/TF ratio suggests relief of myocardial ischemia after CABG.
- Observed changes indicate a potential delay in the recovery of cardiac autonomic activity post-surgery.
Abstract:
This study was performed to assess the effects of coronary artery bypass grafting (CABG) on the ultra-low (ULF) and very low (VLF) frequency components of heart rate variability (HRV). Forty-nine CABG patients (aged from 38 to 77 years) were examined by 24-h ambulatory electrocardiographic (AECG) monitoring, both preoperatively and 4 weeks after CABG. HRV spectral components were obtained by maximum entropy method analysis. Then the ULF, VLF, low frequency (LF), high frequency (HF) and total frequency (TF) components were compared before and after CABG. The average 24-h heart rate increased significantly after CABG (69+/-11.5 vs 82.9+/-10.9 beats per minute [bpm], P < 0.0001). The power of the ULF, VLF, and LF spectral components showed a decrease after surgery (2,859.9 vs 1,601.2 ms2, P<0.0001, 1,215.0 vs 572.3 ms2, P<0.0001, and 260.3 vs 125.9 ms2, P< 0.002, respectively), but the HF power did not show any significant change (98.7 vs 125.9 ms2, NS). Analysis of the normalized ratio of the ULF component (ULF/TF ratio) revealed a significant increase postoperatively (0.6496+/-0.0931 vs 0.7003+/-0.1338, P < 0.0001), but the VLF/TF and LF/TF ratios decreased after CABG (from 0.2671+/-0.0689 to 0.2040+/-0.0832, P< 0.0001 and from 0.0568+/-0.0290 to 0.0429+/-0.0232, P< 0.0088, respectively). In contrast, there was no significant alteration in the HF/TF ratio. These results suggest that recovery of cardiac autonomic activity is delayed after surgery. However, improvement of the ULF/TF ratio, one of the prognostic indicators for patients with cardiac disease, should be related to the relief of myocardial ischemia by CABG.