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Heart rate power spectral analysis in patients before and 6 weeks after coronary artery bypass grafting
J Bellwon1, J Siebert, J Rogowski
1Ist Dept. of Cardiology, Medical University of Gdańsk, Poland.
Insights
Coronary artery bypass grafting (CABG) significantly improves cardiac vagal activity, particularly in the standing position. This enhancement in heart rate variability (HRV) suggests a positive impact on cardiovascular health post-surgery.
Area of Science:
- Cardiology
- Autonomic Nervous System Function
Background:
- Decreased cardiac vagal activity is a recognized risk factor for coronary artery disease.
- Heart rate variability (HRV) is a key indicator of autonomic function and cardiac health.
Purpose of the Study:
- To investigate the impact of coronary artery bypass grafting (CABG) on heart rate variability (HRV).
- To assess changes in HRV parameters before and 6 weeks after CABG, focusing on autonomic modulation.
Main Methods:
- 34 patients undergoing CABG had their ECGs recorded in supine and standing positions with controlled breathing.
- Heart rate variability (HRV) power spectrum analysis utilized fast Fourier transformation.
- Key HRV parameters analyzed included total spectral power (TPS), VLF, LF, HF, LF/HF ratio, and their percentage fractions.
Main Results:
- Before CABG, significant attenuation of HRV spectral components occurred during orthostatic load (standing vs. supine).
- Post-CABG, these orthostatic changes were not significant, indicating improved autonomic stability.
- Specifically, HF and %HF significantly increased in the standing position after CABG.
Conclusions:
- Coronary artery bypass grafting (CABG) appears to improve cardiac vagal activity, especially under orthostatic stress.
- The observed improvements in HRV suggest enhanced autonomic regulation following CABG.
- These findings highlight CABG's potential benefits beyond revascularization, impacting autonomic control of the heart.
Abstract:
Decreased cardiac vagal activity is a known risk factor in coronary artery disease. The aim of our study was to determine the effect of coronary artery bypass grafting (CABG) on heart rate variability (HRV) before and 6 weeks after CABG. The study group consisted of 34 patients (4 women, 30 men, mean age 56 +/- 9 years). ECGs were recorded in 10 minutes periods in both supine and standing position with controlled breathing rate (0.25Hz). The analysis of HRV power spectrum was done by means of fast Fourier transformation. The total spectral power (TPS), power in very low frequency band (VLF: < 0.05 Hz), low frequency band (LF:0.05-0.15Hz), high frequency band (HF:0.15-0.5Hz), LF/HF ratio and percentage fraction of total power in these frequency bands (%VLF, %LF, %HF) were analysed. Significant attenuation of all spectral components of HRV were found during orthostatic load before CABG (p < 0.05). TPS, VLF, LF, %HF decreased in standing position to about half of their level in supine position, HF decreased to as little as one fourth, while LF/HF ratio and %LF increased significantly (p < 0.05). After the CABG these changes were not significant. We have found significant increase of HF (p < 0.05) and %HF (p < 0.01) in standing position after the CABG. The results suggest that CABG causes an improvement in cardiac vagal activity especially in standing position.