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Published on: August 2, 2019
Nonlinear heart rate variability in CABG patients and the preconditioning effect
Zhong-Kai Wu1, Saila Vikman, Jari Laurikka
1Department of Cardiac Surgery, Affiliated 1st Hospital, Sun Yat-sen University, GuangZhou, China. lozhwu@uta.fi
Insights
Ischemic preconditioning (IP) attenuates autonomic dysfunction after cardiac surgery. This protective mechanism, indicated by nonlinear heart rate variability (HRV), improves patient outcomes and reduces arrhythmias.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Surgical Outcomes
Background:
- Heart rate variability (HRV) is a key noninvasive measure for assessing cardiac autonomic control.
- The role of nonlinear HRV in patients undergoing cardiopulmonary bypass (CPB) remains underexplored.
- Myocardial ischemia can impact HRV, suggesting a potential link with ischemic preconditioning (IP).
Purpose of the Study:
- To investigate the influence of ischemic preconditioning (IP) on cardiac autonomic regulation in patients undergoing coronary artery bypass grafting (CABG).
- To determine if IP can mitigate the autonomic dysfunction observed after CABG surgery.
- To assess the predictive value of nonlinear HRV measures for postoperative outcomes.
Main Methods:
- Eighty-six CABG patients were randomized into control and IP groups.
- IP group received two cycles of 2-minute ischemia and 3-minute reperfusion.
- Holter monitoring was used for pre- and postoperative HRV analysis, including linear and nonlinear measures.
Main Results:
- Postoperative suppression of time/frequency domain HRV and nonlinear index alpha1 was observed in both groups.
- Lower alpha1 predicted higher incidence of postoperative atrial fibrillation (AF) and worse outcomes.
- The suppressed alpha1 was attenuated in the IP group compared to controls (P=0.008).
- IP significantly reduced postoperative arrhythmias and improved outcomes, with no significant changes in linear HRV measures.
Conclusions:
- Cardiac autonomic regulation is impaired following CABG.
- Nonlinear HRV index alpha1 is a sensitive predictor of postoperative outcomes in CABG patients.
- IP alleviates extreme autonomic responses post-surgery, indicating its involvement in the protective mechanism.
Objective:
Heart rate variability (HRV) is the most frequently used noninvasive diagnostic method in the assessment of cardiac autonomic control. The clinical relevance of HRV, especially nonlinear HRV in CPB patients has not been well studied. Short brief myocardial ischemia has been reported to influence HRV. We therefore hypothesis that the protective mechanism of ischemic preconditioning (IP) may involve in cardiac autonomic regulation.
Methods:
Eighty-six CABG patients were randomized into a control and an IP group. The IP patients received two periods of 2-min ischemia followed by 3-min reperfusion by aortic cross-clamped. Holter data were collected in 86 CABG patients before and after surgery. Arrhythmias, linear and nonlinear HRV measures were analyzed.
Results:
All time and frequency domain HRV variables as well as nonlinear indexes of HRV, the short-term (4-11 beats) scaling exponent alpha1, were suppressed significantly after surgery in both study groups. The lower pre- and postoperative exponent alpha1 predict the higher incidence of postoperative AF and worse postoperative outcome. The suppressed exponent alpha1 was attenuated in the IP group as compared to controls (P = 0.008). No other differences were observed in the changes in linear HRV measures between the groups. IP significantly reduced the incidence of postoperative arrhythmias and improved postoperative outcome.
Conclusions:
The present findings show that cardiac autonomic regulation is impaired after CABG. Nonlinear HRV exponent alpha1 is a more sensitive measure to predict the postoperative outcome in CABG patients. IP alleviates the extreme autonomic reactions after surgery, suggesting that cardiac autonomic regulation is involved in the IP protective mechanism.
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