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Histological Quantification of Chronic Myocardial Infarct in Rats
Published on: December 11, 2016
Evaluation of coronary collateral circulation in early ischemia in rat hearts. A morphological study
1Central Institute for Electron Microscopic Researches, Nippon Medical School, Tokyo, Japan.
Insights
Collateral circulation in the heart becomes functional within 15-30 minutes after coronary artery occlusion. This developing blood flow network helps prevent early myocardial infarction.
Area of Science:
- Cardiovascular Biology
- Myocardial Ischemia Research
- Vascular Anatomy
Background:
- Coronary artery ligation induces myocardial ischemia, leading to potential infarction.
- Understanding collateral circulation is crucial for mitigating ischemic damage.
- Early functional assessment of collateral pathways remains an area of investigation.
Purpose of the Study:
- To investigate the temporal development and functional capacity of collateral circulation following acute coronary artery occlusion.
- To correlate histological and morphological changes with the onset and extent of collateral blood flow in ischemic myocardium.
- To evaluate the protective role of early collateral circulation against myocardial infarction.
Main Methods:
- Histological examination of rat left ventricular free walls after coronary artery ligation.
- Utilizing auto-injected tracers for light microscopy to visualize collateral circulation.
- Employing PAS staining and transmission electron microscopy to assess myocardial morphology and damage.
Main Results:
- Collateral circulation tracers appeared in veins within 15 minutes and capillaries by 30 minutes post-occlusion.
- Functional collateral circulation was evident between 15 and 30 minutes, progressively increasing thereafter.
- Dye distribution indicated collateral flow reached all myocardial layers by 3 hours, correlating with PAS staining.
- Myocardial damage was heterogeneous, with collateral flow present in areas of less severe damage.
Conclusions:
- Collateral circulation becomes functional early, within 15-30 minutes of coronary occlusion.
- The development of collateral pathways, including venous backflow and superficial space flow, plays a vital role in preventing early myocardial infarction.
- These findings highlight the potential therapeutic significance of promoting early collateralization in ischemic heart disease.
Abstract:
Histological changes were examined in the left ventricular free wall of the heart in 40 rats after ligation of the distal anterior descending coronary artery for 15, 30 minutes and 1, 2, 3, 4, 5, 6 hours. Auto-injection of tracers for light microscopy was used to examine the development of collateral circulation. Morphological changes of the ischemic myocardium were observed by PAS staining and transmission electron microscopy. Fifteen minutes after coronary occlusion, the dye was observed in the vein of the ischemic zone; however, 30 minutes after coronary occlusion, the dye appeared in the capillaries of the outer-third layer. These findings suggested that the collateral circulation becomes functional between 15 and 30 minutes after coronary occlusion. Collateral circulation increased gradually in the capillaries of the ischemic zone. Thirty minutes after coronary occlusion the dye was seen only in the outer-third layer of the ventricular ischemic zone. One hour after occlusion, the dye appeared in the superficial space and the middle-third layer. Three hours after occlusion, the dye was seen in all layers of the ischemic zone. The dye appeared in the ischemic zone, where myocardium damage was not homogeneous. The positive reaction obtained by PAS staining corresponded with the capillaries, veins and superficial spaces in which the dye was evident. These results suggest that collateral circulation, verural back flow and superficial space flow are able to prevent myocardial infarction in early ischemia.
