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[Factors affecting exercise capacity after coronary bypass grafting]
T Murabayashi1, H Itoh, M Kato
1Second Department of Internal Medicine, St. Marianna University, School of Medicine, Kawasaki, Japan.
Insights
Cardiac reserve and peripheral muscle factors significantly contribute to exercise capacity after Coronary Artery Bypass Grafting (CABG). Oxygen delivery is crucial for improving exercise capacity in the initial months post-surgery.
Area of Science:
- Cardiology
- Exercise Physiology
- Rehabilitation Medicine
Context:
- Coronary Artery Bypass Grafting (CABG) is a major cardiovascular surgery.
- Post-operative recovery and exercise capacity are critical for patient outcomes.
- Limited understanding exists regarding the specific contributions of cardiac and peripheral factors to exercise capacity after CABG.
Purpose:
- To investigate the roles of cardiac reserve and peripheral muscle function in determining exercise capacity following CABG.
- To assess changes in exercise parameters, cardiac index, and muscle mass over time post-CABG.
- To identify key physiological determinants of improved exercise capacity after CABG.
Summary:
- This study evaluated 19 patients post-CABG using exercise tests at 1 week, 3 weeks, and 3 months.
- Measurements included peak oxygen uptake (peak VO2), anaerobic threshold (AT), cardiac index (CI), and thigh muscle area.
- Results indicate that both cardiac reserve (delta CI) and peripheral factors (muscle area) contribute to exercise capacity, with oxygen delivery being particularly important.
Impact:
- Findings highlight the importance of a combined approach addressing both cardiac and peripheral factors for optimizing post-CABG rehabilitation.
- This research provides insights into the physiological adaptations influencing exercise capacity, guiding clinical interventions.
- Understanding these contributions can lead to more personalized and effective exercise programs for CABG patients.
Abstract:
In order to determine the contribution of cardiac reserve and the peripheral muscle to exercise capacity in patients after Coronary Artery Bypass Grafting (CABG), 19 patients (18 males, 1 female, mean age 63.3 +/- 7.1 years, mean numbers of grafting 2.5 +/- 0.8) performed exercise tests at 1 week, 3 weeks, and 3 months after CABG. Ventilatory gas was analyzed throughout the testing and anaerobic threshold (AT) and peak oxygen uptake (peak VO2) was determined. During exercise testing, the cardiac index (CI) was measured, and the change in CI during exercise, delta CI = (CI at peak exercise) (CI at rest), was calculated. O2 delivery was derived from the product of CO and the oxygen content of arterial blood at peak exercise. The sectional area of the thigh muscles at the level of 10 cm above the patella was measured using a computed tomography before each test. Average peak VO2 at 1 week after CABG was 867 +/- 171 ml/min and it increased to 1,214 +/- 246 ml/min at 6 months. Average AT did not change from 1 week to 3 weeks, however, it increased significantly from 665 +/- 122 ml/min at 3 weeks to 873 +/- 181 ml/min at 6 months. The muscle area of the thigh increased significantly from 170 +/- 24 cm2 at 3 weeks after CABG to 186 +/- 27 cm2 at 3 months. delta CI showed a tendency to increase from 6.6 +/- 1.2 l/min/m2 at 1 week after CABG to 7.3 +/- 1.3 l/min/m2 at 3 weeks, and also showed a tendency to increase from 3 weeks to 6 months. Peak VO2 and AT correlated to delta CI at 1 weeks and also it correlated significantly to both the muscle area of the thigh and delta CI at 3 weeks, 3 months, and 6 months after CABG. The delta value of peak VO2 from 1 week to 3 weeks showed a significant correlation to those of delta CI and O2 delivery. Moreover, the delta values of peak VO2 and AT from 3 weeks to 3 months showed a correlation to those of delta CI and O2 delivery. These results suggest that both cardiac reserve and peripheral factors contribute to the exercise capacity up to 3 months after CABG, and, in particular, O2 delivery are important to increase exercise capacity.