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Recovery of heart rate variability profile in patients after coronary artery surgery
T Komatsu1, T Kimura, K Nishiwaki
1Department of Anesthesiology, Nagoya University School of Medicine, Japan. tkomatsu@med.nagoya-u.ac.jp
Insights
Heart rate variability (HRV) profiles show altered neural regulation after coronary artery surgery (CAS). While some HRV measures normalize by 28 days, overall variability remains depressed, indicating incomplete recovery of cardiovascular homeostasis.
Area of Science:
- Cardiology
- Autonomic Nervous System Function
- Postoperative Recovery
Background:
- Heart rate variability (HRV) is a key indicator of autonomic nervous system (ANS) control over cardiac function.
- Coronary artery surgery (CAS) can significantly impact ANS function and cardiovascular homeostasis.
- Understanding the temporal profile of HRV changes post-CAS is crucial for assessing recovery and patient outcomes.
Purpose of the Study:
- To investigate the time course of heart rate variability (HRV) changes following coronary artery surgery (CAS).
- To characterize different recovery profiles of HRV in the early and late postoperative periods.
- To assess the extent of cardiovascular homeostasis recovery after CAS through HRV analysis.
Main Methods:
- Spectral analysis of R-R intervals was performed on preoperative and multiple postoperative days (1-28).
- Analysis included low-frequency (LF) and high-frequency (HF) power spectral components.
- Fractal slope and sympathovagal slope were calculated to assess 1/f characteristics of HRV.
Main Results:
- Three distinct HRV recovery profiles were identified: early (Days 1-6), subsequent (Days 7-21), and later (Day 28).
- Early recovery showed reduced LF, HF, and sympathovagal slope, with increased fractal slope.
- By Day 28, spectral components remained reduced, but sympathovagal and fractal slopes normalized, indicating incomplete recovery.
Conclusions:
- Coronary artery surgery leads to significant, albeit incomplete, alterations in cardiovascular homeostasis, reflected in depressed HRV up to 28 days postoperatively.
- While some HRV parameters normalize earlier, overall neural regulation of cardiac function remains impaired.
- Further research is needed to correlate depressed HRV with clinical outcomes post-CAS.
Unlabelled:
We examined the different characteristics of heart rate variability (HRV) to define the time course of HRV profile after coronary artery surgery (CAS). Spectral analysis of HRV was performed on a 512-s segment of R-R intervals of the electrocardiogram on the preoperative day and on Postoperative Days 1, 2, 3, 4, 5, 6, 7, 14, 21, and 28. Power spectral area was divided into low (0.04-0.15 Hz; LF)- and high (0.15-0.5 Hz; HF)-frequency components. Fractal slope and sympathovagal slope of 1/f characteristics of HRV were determined in two different frequency ranges (from 0.01 to 0.15 Hz and from 0.01 to 0.5 Hz, respectively). Three recovery profiles of HRV were identified. Early HRV recovery profiles (Postoperative Days 1-6) included reduction in LF, HF, and sympathovagal slope, as well as an increase in fractal slope. Subsequent HRV recovery profiles (Postoperative Days 7-21) revealed reductions in LF, HF, and sympathovagal slope. Fractal slope became normal. Later HRV recovery profiles (Postoperative Day 28) demonstrated that all spectral components of HRV remained reduced, but sympathovagal and fractal slopes became normal. These changes in the HRV profile after CAS suggest significant postoperative alterations in cardiovascular homeostasis with significant but incomplete recovery during the first 28 postoperative days.
Implications:
Heart rate variability reflects normal neural regulation of cardiac function. This variability remains depressed as long as 28 days after coronary artery bypass surgery, but can recover as early as 1 wk postoperatively. Despite implied loss of normal neural regulation of cardiac function, a specific correlation between depressed heart rate variability and outcomes was not performed.