Long-term alterations of heart rate dynamics after coronary artery bypass graft surgery

Area of Science:

• Cardiology
• Medical Engineering
• Physiology

Background:

• Reduced heart rate (HR) variability is linked to increased morbidity in diverse patient groups.
• Coronary artery bypass graft (CABG) surgery is a common procedure for managing coronary artery disease.
• Understanding post-CABG cardiac autonomic function is crucial for patient management.

Purpose of the Study:

• To investigate long-term alterations in heart rate (HR) variability and fractal HR behavior following coronary artery bypass graft (CABG) surgery.
• To assess changes in time and frequency domain HR variability measures.
• To evaluate fractal dynamics, complexity, and predictability of HR post-CABG.

Main Methods:

• Continuous 24-h electrocardiograph (ECG) recordings were obtained from 25 elective CABG patients.
• Measurements were taken 1 week before surgery, and at 6 weeks, 6 months, and 12 months post-surgery.
• Analysis included HR variability indices, short-term fractal scaling exponent (alpha1), approximate entropy, and beta-slope.

Main Results:

• Significant decreases in high, low, very low, and ultra low frequency powers of HR variability were observed post-CABG, persisting up to 12 months.
• The fractal scaling exponent (alpha1) decreased at 6 weeks post-CABG but returned to baseline by 6 months.
• Approximate entropy, indicating HR complexity, decreased significantly over the study period, suggesting more predictable HR dynamics.

Conclusions:

• CABG surgery leads to persistent, long-term reductions in heart rate variability and complexity.
• The fractal organization of HR dynamics remains stable, but overall complexity diminishes post-surgery.
• The clinical significance of these long-term HR dynamic changes after CABG for patient outcomes requires further investigation.