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Time constraints in the emergency coronary bypass surgery for acute evolving myocardial infarction
Insights
Emergency coronary artery bypass surgery for evolving myocardial infarction offers survival benefits, especially with early intervention (under 3 hours ischemia). One hour of reperfusion before bypass weaning is crucial for optimal outcomes in these critical cardiac patients.
Area of Science:
- Cardiovascular Surgery
- Interventional Cardiology
- Myocardial Infarction Research
Background:
- Evolving myocardial infarction presents a critical window for intervention.
- Emergency coronary artery bypass grafting (CABG) is an option when intracoronary thrombolysis is not feasible.
- Patient outcomes in evolving myocardial infarction depend heavily on reperfusion strategies and timing.
Purpose of the Study:
- To evaluate the efficacy and outcomes of emergency coronary artery bypass grafting in patients with evolving myocardial infarction.
- To compare the effects of early versus late surgical intervention on infarct size and cardiac function.
- To determine the importance of intraoperative reperfusion strategies in improving myocardial recovery.
Main Methods:
- Retrospective analysis of 44 patients undergoing emergency CABG for evolving myocardial infarction.
- Comparison of early (<3 hours ischemia) versus late (≥3 hours ischemia) surgery groups.
- Assessment of infarct size, regional ejection fraction, and ultrastructural/biochemical myocardial changes.
- Long-term follow-up for cardiac survival and angina-free status.
Main Results:
- Operative mortality was 6.8%; 30-month survival was 93.2%.
- Early surgery (<3 hours ischemia) resulted in smaller infarcts and better regional ejection fraction compared to controls.
- Ultrastructural and biochemical analyses showed reversible changes with early surgery and reperfusion, unlike late surgery.
- One hour of empty beating heart reperfusion before bypass weaning was essential for recovery in the early group.
Conclusions:
- Emergency coronary artery bypass grafting can be beneficial for evolving myocardial infarction when thrombolysis is contraindicated.
- Optimal outcomes are associated with early surgical intervention (less than 3 hours of ischemia).
- Intraoperative reperfusion, specifically one hour of empty beating heart reperfusion, is critical for myocardial salvage.
Abstract:
Fourty four patients underwent emergency coronary grafting for evolving myocardial infarction. All patients but one had undergone coronary angiography before the new infarction, 50% were in cardiogenic shock or under cardiopulmonary resuscitation. The mean time interval between the onset symptoms and opening of the bypass to the threatened area was 171 minutes. The operative mortality was 6.8%. At 30 months after surgery, the cardiac actuarial survival was 93.2%, the angina free group 94.2% of the operative survivors. Infarct size and regional ejection fraction of these patients at late follow-up were compared to those of controls treated conventionally for acute infarction. The thallium defects were smaller and the regional ejection fraction of the involved segment was higher after early surgery (less than 3 hours ischemia) than in controls. In the late surgery group the thallium defects and the regional ejection fractions were similar. Ultrastructural studies on biopsy samples taken from the center of the threatened area show reversible changes in the early surgery group but irreversible mitochondrial damage and cell membrane rupture in the late surgery group. Biochemical analysis of similar cardiac biopsies shows recovery after one hour empty beating reperfusion but only in the early surgery group. Our results suggest that coronary surgery can be beneficial to the patient with an evolving myocardial infarction, if the clinical situation does not permit intracoronary thrombolysis. However, one hour reperfusion of the empty beating heart before weaning off bypass is essential. The time constraints for both emergency surgery or thrombolysis are similar.