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Controlled reperfusion following regional ischemia
1Department of Surgery, Columbia University, College of Physicians and Surgeons, New York, NY.
Insights
Reperfusion of ischemic heart muscle in a beating heart model worsened ventricular function. Arrested heart reperfusion with cardioplegia prevented this damage, preserving heart function.
Area of Science:
- Cardiovascular Science
- Myocardial Reperfusion Injury
- Cardiac Surgery
Background:
- Advances in reperfusion therapies for acute coronary occlusion necessitate understanding their impact on myocardial function.
- Interest in revascularizing ischemic myocardium has grown due to improved fibrinolytic agents and angioplasty techniques.
Purpose of the Study:
- To investigate changes in global ventricular function, mass, and compliance during acute coronary occlusion and subsequent reperfusion.
- To compare the effects of reperfusion in a beating heart versus an arrested heart using blood cardioplegia.
Main Methods:
- Acute coronary occlusion was induced in 17 dogs on cardiopulmonary bypass for 45 minutes.
- Reperfusion was achieved in 12 dogs by releasing a coronary snare in the beating heart.
- In 5 dogs, reperfusion occurred in an arrested heart with a 10-minute infusion of blood potassium cardioplegia.
Main Results:
- Coronary occlusion significantly decreased stroke work index and left ventricular (LV) mass, with no change in compliance.
- Reperfusion in the beating heart increased LV mass and decreased LV compliance compared to pre-ischemia values.
- Reperfusion with blood cardioplegia in the arrested heart maintained LV mass and compliance at control levels.
Conclusions:
- Revascularization of acutely ischemic myocardium in a beating heart model exacerbates LV dysfunction by increasing mass and reducing compliance.
- Using blood cardioplegia for reperfusion in an arrested heart effectively avoids this post-reperfusion damage.
- This suggests a protective strategy for myocardial preservation during cardiac interventions.
Abstract:
The ability to reverse acute coronary occlusion with fibrinolytic agents and percutaneous transluminal angioplasty has increased interest in the revascularization of ischemic myocardium. This study defines changes in global ventricular function, mass, and compliance during acute coronary occlusion and following reperfusion with blood in the beating and arrested heart. In 17 dogs on cardiopulmonary bypass, the proximal left anterior descending coronary artery was occluded for 45 minutes. In 12 dogs, flow was reestablished by releasing the coronary snare in the beating heart. In the other 5 dogs, the snare was released during a continuous 10-minute infusion of blood potassium cardioplegia in the arrested heart. Coronary occlusion resulted in significant decreases in stroke work index and left ventricular (LV) mass, but compliance was unchanged. Reperfusion in the beating heart increased LV mass compared with the values measured before ischemia (104 +/- 5 versus 95 +/- 5 gm; p less than 0.05) and decreased LV compliance (39 +/- 4 versus 53 +/- 4 ml at LV end-diastolic pressure of 8 mm Hg; p less than 0.05). In contrast, with blood cardioplegia-based reperfusion in the arrested heart, LV mass and LV compliance remained unchanged from control values. We conclude that revascularization of acutely ischemic myocardium in the beating heart further impairs LV function by increasing LV mass and decreasing compliance. This damage can be avoided by reperfusion with blood cardioplegia in the arrested heart.