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Microvasculature sparing with controlled reperfusion of ischemic myocardium
R E Mrak1, M L Murphy, C F Peng
1Division of Pathology, John L. McClellan Memorial Veterans Hospital, Little Rock, AR.
Abstract:
Reperfusion of ischemic myocardium may result in further ultrastructural damage to cardiac fibers, a phenomenon known as reperfusion injury. We have recently shown that controlled reperfusion, with maintenance of reperfusion flow rates near preischemia levels, prevents much of this reperfusion damage. This observation suggests that mechanical damage to the myocardial microvasculature is important in the pathogenesis of reperfusion injury. In this study, we have used electron microscopy to examine the microcirculation of ischemic, reperfused pig myocardium under conditions of uncontrolled and controlled reperfusion. Animals receiving uncontrolled reperfusion (reperfusion flow 3-4 times preischemia levels) showed ultrastructural damage to myocardial capillaries after 1 hour of ischemia and 2 hours of reperfusion. This damage was manifested as depletion of endothelial cell pinocytotic vesicles, plugging of capillaries by erythrocytes, leukocytes, and fibrin-containing microthrombi, and perivascular microhemorrhages. None of these changes were found in animals receiving controlled coronary artery reperfusion. We conclude that mechanical damage to the myocardial microvasculature is important in the pathogenesis of reperfusion injury and that such damage is obviated under conditions of controlled coronary artery flow during reperfusion.
Insights
Controlled reperfusion prevents cardiac microvascular damage during reperfusion injury. Maintaining flow near pre-ischemia levels protects myocardial capillaries from injury, unlike uncontrolled reperfusion.
Area of Science:
- Cardiovascular Science
- Pathology
- Microcirculation Research
Background:
- Reperfusion of ischemic myocardium can cause further damage, termed reperfusion injury.
- Previous research indicates controlled reperfusion may prevent this damage.
- Mechanical stress on the microvasculature is a suspected contributor to reperfusion injury.
Purpose of the Study:
- To investigate the role of mechanical damage in reperfusion injury.
- To compare microcirculatory changes during uncontrolled versus controlled reperfusion in ischemic myocardium.
Main Methods:
- Utilized electron microscopy to examine pig myocardium microcirculation.
- Compared ultrastructural changes in capillaries after ischemia and reperfusion under two different flow conditions.
Main Results:
- Uncontrolled reperfusion (3-4x pre-ischemia flow) caused capillary damage, including endothelial cell changes, microthrombi, and hemorrhages.
- Controlled reperfusion (near pre-ischemia levels) showed no significant capillary damage.
- Observed depletion of endothelial pinocytotic vesicles and microhemorrhages in uncontrolled reperfusion.
Conclusions:
- Mechanical damage to the myocardial microvasculature is a key factor in reperfusion injury pathogenesis.
- Controlled coronary artery reperfusion effectively prevents microvascular damage.
- Maintaining physiological flow rates during reperfusion is crucial for preserving myocardial microcirculation.