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Moderate normovolaemic haemodilution increases regional myocardial blood flow but has no effect on experimental
Insights
Moderate hemodilution did not alter infarct size in cats with left anterior descending coronary artery occlusion. While hemodilution increased blood flow in non-ischemic areas, it did not improve perfusion in severely ischemic regions.
Area of Science:
- Cardiovascular Physiology
- Ischemic Heart Disease Research
Background:
- Myocardial infarction (MI) is a leading cause of mortality.
- Understanding factors that influence infarct size is crucial for developing therapeutic strategies.
- Regional myocardial blood flow (MBF) and hematocrit levels are critical determinants of infarct size.
Purpose of the Study:
- To investigate the effect of hemodilution on regional myocardial blood flow and infarct size following left anterior descending coronary artery (LAD) occlusion in an animal model.
- To determine if reducing hematocrit through hemodilution can mitigate myocardial damage in the context of acute ischemia.
Main Methods:
- Regional MBF was measured using radioactive microspheres in anesthetized cats before and at multiple time points after LAD occlusion.
- One group underwent normovolemic hemodilution with dextran 40, reducing hematocrit by 20-25%.
- Infarct size was quantified 12 hours post-occlusion using the tetrazolium staining technique.
Main Results:
- Hemodilution significantly increased blood flow in non-ischemic myocardium and the border zone.
- Perfusion in severely ischemic myocardium, reliant on collateral blood flow, was not significantly affected by hemodilution.
- The final infarct size was comparable between the hemodiluted group (27 ± 4%) and the control group (28 ± 3%) 12 hours after LAD ligation.
Conclusions:
- Moderate normovolemic hemodilution does not reduce infarct size in this model of acute myocardial infarction.
- The lack of benefit may be attributed to the inability of hemodilution to improve blood flow in critically ischemic myocardial regions dependent on collateral circulation.
Abstract:
Regional myocardial blood flow was measured with radioactive microspheres before and 1, 3, 6, and 12 h after occlusion of the left anterior descending coronary artery (LAD) in anaesthetized cats. In one group of cats, 1 h after LAD occlusion, moderate normovolaemic haemodilution was started with a dextran 40 solution, which reduced the haematocrit by 20-25% throughout the rest of the experiment. In the other group, the haematocrit was kept at the original level. Infarct size was measured planimetrically 12 h after the coronary ligation, using the tetrazolium staining technique for disclosing the ischaemic myocardium. Haemodilution increased blood flow in the non-ischaemic myocardium and in the so-called 'border zone' comprising both normal, and ischaemic tissue. However, in the severely ischaemic myocardium dependent on collateral blood flow, where there was no admixture of non-ischaemic myocardium, the blood perfusion was not significantly affected by the haemodilution. After 12 h of ischaemia the infarct size in the control group was fully comparable with that in the haemodiluted group: 28 +/- 3 and 27 +/- 4 (percentage of the left ventricle, mean +/- SEM), respectively.