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RR interval dynamics before atrial fibrillation in patients after coronary artery bypass graft surgery
C W Hogue1, P P Domitrovich, P K Stein
1Department of Anesthesiology, Washington University School of Medicine, St Louis, MO 63110, USA. hoguec@notes.wustl.edu
Insights
Postoperative atrial fibrillation after heart surgery is predicted by higher heart rate and lower heart rate complexity. Decreased approximate entropy (ApEn) may help identify patients at risk.
Area of Science:
- Cardiology
- Cardiac Surgery
- Autonomic Nervous System
Background:
- Atrial fibrillation/flutter (AF) is a common complication following coronary artery bypass graft (CABG) surgery.
- AF increases healthcare costs and patient morbidity.
- Heart rate variability (HRV) reflects cardiac sympathovagal balance and may change before AF onset.
Purpose of the Study:
- To investigate if heart rate variability (HRV) is altered before postoperative AF after CABG.
- To determine if nonlinear HRV measures, specifically approximate entropy (ApEn), can predict AF.
- To assess the predictive value of HRV and ApEn for AF in CABG patients.
Main Methods:
- Analysis of HRV in 20-minute intervals preceding AF onset in 24 episodes from 18 patients.
- Comparison with 18 matched control subjects who did not develop AF.
- Logistic regression analysis to identify independent predictors of AF, including heart rate and ApEn.
Main Results:
- Increased heart rate and decreased ApEn were independently associated with AF.
- Heart rate dynamics showed varied patterns (increased or decreased RR interval variation) before AF.
- Lower heart rate complexity (decreased ApEn) was observed in patients who developed AF.
Conclusions:
- Higher heart rate and lower heart rate complexity in the hour before AF are independent predictors of AF post-CABG.
- Decreased ApEn may serve as a useful tool for risk stratification in CABG patients.
- ApEn provides insights into autonomic conditions preceding AF, regardless of traditional HRV measures.
Background:
Atrial fibrillation/flutter (AF) is a frequent complication of coronary artery bypass graft surgery (CABG) that leads to increased costs and morbidity. We hypothesized that heart rate variability (HRV), an indicator of cardiac sympathovagal balance, is altered before the onset of postoperative AF. Because nonlinear methods of HRV analysis provide information about heart rate dynamics not evident from usual HRV measures, we also hypothesized that approximate entropy (ApEn), a nonlinear measure of HRV, might have predictive value.
Methods And Results:
Analysis of HRV was performed in 3 sequential 20-minute intervals preceding the onset of postoperative AF (24 episodes in 18 patients). These data were compared with corresponding intervals in 18 sex- and age-matched postoperative control subjects who did not develop AF. Patients had left ventricular ejection fractions >45% before surgery and were not receiving beta-blockers during ambulatory ECG monitoring after surgery. Logistic regression demonstrated that on the basis of averaged values for the three 20-minute intervals, increased heart rate and decreased ApEn were independently associated with AF. Heart rate dynamics before AF was associated with either lower (n= 19) or higher (n=5) RR interval variation by traditional measures of HRV or quantitative Poincaré analysis, suggesting the possibility of divergent autonomic conditions before AF onset.
Conclusions:
In the hour before AF after CABG surgery, higher heart rate and lower heart rate complexity compared with values in control patients were independent predictors of AF. Decreased ApEn occurs in patients with either increased or decreased HRV by traditional measures and may provide a useful tool for risk stratification or investigation of mechanisms.