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Time course of effective interventional left heart assist for limitation of evolving myocardial infarction
Insights
Pulsatile left atrial-femoral artery bypass effectively limits heart attack (myocardial infarction) expansion when initiated up to 6 hours after coronary artery occlusion. This intervention shows promise for patients experiencing evolving myocardial infarction.
Area of Science:
- Cardiovascular Research
- Ischemic Heart Disease
- Surgical Intervention
Background:
- Previous studies demonstrated the efficacy of pulsatile left atrial-femoral artery bypass in limiting infarct size when initiated within 2 hours of left anterior descending coronary artery occlusion.
- The clinical relevance of this intervention is limited by the need to assess its effectiveness after longer, more pertinent ischemic periods.
Purpose of the Study:
- To investigate the efficacy of pulsatile left atrial-femoral artery bypass in limiting infarct expansion after prolonged periods of initial ischemia.
- To determine the maximum permissible ischemic time delay for myocardial salvage using this bypass technique in a clinical context.
Main Methods:
- Seventy-three open-chest adult dogs underwent baseline hemodynamic, tension-time index, and regional myocardial blood flow measurements.
- The left anterior descending coronary artery was ligated for 15 minutes, 1, 2, 4, or 6 hours.
- Experimental groups received 4 hours of pulsatile left atrial-femoral artery bypass post-ligation; control groups had extended ischemia.
- Area at risk was identified using gentian violet, and infarct size was delineated with triphenyltetrazium chloride.
Main Results:
- A significant reduction in infarct size relative to the area at risk was observed in all experimental groups compared to their respective control groups for ischemic periods less than 6 hours.
- The bypass intervention demonstrated significant myocardial salvage across various clinically relevant ischemic durations.
Conclusions:
- Pulsatile left atrial-femoral artery bypass is effective in salvaging myocardium even when initiated after extended ischemic periods (up to 6 hours).
- The findings support the development of percutaneous techniques for applying this modality to patients with evolving myocardial infarction, suggesting a clinically relevant time window for intervention.
Abstract:
Previous work has shown that if pulsatile left atrial-femoral artery bypass is instituted after occlusion of the left anterior descending coronary artery for from 15 minutes to 2 hours, it can significantly limit the size of the infarct resulting 4 hours later. This study investigated whether pulsatile left atrial-femoral artery bypass begun after more clinically pertinent periods of initial ischemia can still significantly limit infarct expansion. After baseline measurements of hemodynamics, tension-time index, and regional myocardial blood flow in 73 open-chest, adult dogs, the left anterior descending coronary artery was ligated for 15 minutes or 1, 2, 4, or 6 hours of unprotected ischemia. In the five control groups, the initial ischemic period was merely extended for another 4 hours. In the five experimental groups, the animals were placed on pulsatile left atrial-femoral artery bypass for another 4 hours after the initial ischemic period. At the end of each procedure, gentian violet was used to identify the area at risk of infarction, and triphenyltetrazolium chloride was used to delineate the area of infarct. The results showed a significant reduction in the area of infarct as a percentage of the area at risk in each bypass group compared with its control group for all ischemic periods of less than 6 hours. These findings suggest that the maximum permissible ischemic time delay for myocardial salvage by pulsatile left atrial-femoral artery bypass is one which is pertinent in a clinical setting. The results justify continued attempts to develop appropriate techniques for percutaneous application of this modality to patients with an evolving myocardial infarction.