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Warm blood cardioplegia: superior protection after acute myocardial ischemia
1Carlyle Fraser Heart Center, Crawford Long Hospital, Emory University, Atlanta, Georgia.
Insights
Continuous aerobic warm blood cardioplegia (WB) demonstrated superior myocardial protection compared to cold cardioplegia techniques in a canine model. WB significantly improved overall ventricular and diastolic function, reducing myocardial injury and defibrillation needs.
Area of Science:
- Cardiology
- Cardiovascular Surgery
- Biomedical Engineering
Background:
- Myocardial protection during cardiac surgery is crucial for preventing ischemia-reperfusion injury.
- Current clinical practices often involve hypothermic cardioplegia, with varying outcomes.
- Optimizing myocardial protection strategies remains an active area of research.
Purpose of the Study:
- To compare the efficacy of continuous aerobic warm blood cardioplegia (WB) against two cold cardioplegia techniques (cold oxygenated crystalloid cardioplegia - CC, and cold blood cardioplegia - CB) in a canine model of acute myocardial ischemia and revascularization.
- To evaluate the impact of different cardioplegia strategies on myocardial function, energetics, and injury.
- To identify the optimal cardioplegia approach for improved patient outcomes.
Main Methods:
- Eighteen canines were randomized into three groups: CC, CB, and WB (n=6 each).
- All groups underwent systemic hypothermic (CC, CB) or normothermic (WB) cardiopulmonary bypass with cardioplegic arrest.
- A standardized 15-minute warm global ischemia period was followed by left anterior descending coronary artery occlusion and 60-minute cardioplegic arrest, simulating clinical revascularization.
Main Results:
- No significant differences were observed in maximum elastance, myocardial oxygen consumption, edema, or histopathology.
- Continuous aerobic warm blood cardioplegia (WB) group showed significantly better overall ventricular function (preload recruitable stroke work) compared to cold groups (p=0.04).
- Diastolic function was significantly worse in cold groups (p=0.001).
- WB group exhibited less myocardial injury (ST segment elevation, p=0.03) and required fewer countershocks (p=0.03).
Conclusions:
- Continuous aerobic warm blood cardioplegia offers significant advantages in preserving myocardial function post-ischemia compared to traditional cold cardioplegia methods.
- The WB technique demonstrates superior protection against ischemia-reperfusion injury, leading to better ventricular and diastolic function.
- These findings suggest that normothermic, continuous aerobic warm blood cardioplegia may be a more effective myocardial protection strategy in clinical settings.
Abstract:
Three myocardial protection techniques were studied in a canine model of acute myocardial ischemia with subsequent revascularization. Eighteen animals were randomly assigned to one of three treatment regimens: cold oxygenated crystalloid cardioplegia (CC), cold blood cardioplegia with modified reperfusate (CB), and continuous aerobic warm blood cardioplegia (WB) (n = 6 per group). Systemic hypothermic cardiopulmonary bypass (28 degrees C), antegrade arrest, and intermittent retrograde and antegrade delivery were used for the CC and CB groups. Systemic normothermic cardiopulmonary bypass, antegrade arrest, and continuous retrograde delivery were used for the WB group. Fifteen minutes of warm global ischemia was followed by occlusion of the left anterior descending coronary artery (15-minute duration) and simultaneous initiation of cardioplegic arrest (60-minute duration) to simulate clinical revascularization. After reperfusion, the animals were separated from cardiopulmonary bypass. Myocardial function, electrocardiogram, myocardial energetics, water content, histopathology, and defibrillation requirements were compared between groups. There was no significant difference in maximum elastance, myocardial oxygen consumption, myocardial edema, or histopathologic evidence of injury between groups. However, overall ventricular function, assessed by the slope of the preload recruitable stroke work relationship, was significantly better for the WB group (p = 0.04) (WB, 73 +/- 9; CB, 56 +/- 7; CC, 47 +/- 5). Diastolic function as assessed by the slope of the stress-strain relationship was significantly worse overall for the cold groups (p = 0.001) (WB, 20 +/- 2.2; CB, 39 +/- 1.3; CC, 37 +/- 3.1). Myocardial injury as assessed by ST segment elevation (millimeters) was less for the WB group (p = 0.03) (WB, 0.4 +/- 0.3; CB, 1.7 +/- 0.2; CC, 1.6 +/- 0.7). Countershocks necessary to restore sinus rhythm after cross-clamp removal were fewer in the WB group (p = 0.03) (WB, 0.8 +/- 0.3; CB, 4.0 +/- 1.2; CC, 5.5 +/- 1.5). In this model of acute global myocardial ischemia, continuous aerobic warm blood cardioplegia has important advantages over two widely used clinical hypothermic protection techniques.