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Effects of acute coronary artery occlusion on the coronary microcirculation
K C Dellsperger1, D L Janzen, C L Eastham
1Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242.
Insights
Following coronary artery occlusion, coronary microvascular dilation inversely relates to initial diameter. Unlike critical stenosis, acute occlusion eliminates vasodilator reserve from adenosine and EDTA.
Area of Science:
- Cardiovascular Physiology
- Microcirculation Research
- Coronary Artery Disease
Background:
- The precise location of coronary vasodilation after artery occlusion is unclear.
- Understanding microvascular responses is crucial for treating ischemic heart conditions.
Purpose of the Study:
- To identify the microvascular site of vasodilator reserve after critical stenosis and coronary artery occlusion.
- To assess the effects of adenosine and EDTA on coronary microvessels under these conditions.
Main Methods:
- Intravital epiillumination microscopy used in 33 dogs.
- Measurements taken at baseline, critical stenosis, and at 30, 60, 120 minutes post-occlusion.
- Epicardial application of adenosine and EDTA to assess vasodilator reserve.
Main Results:
- After critical stenosis, EDTA dilated all microvessel sizes; adenosine only dilated vessels <150 microns.
- Post-occlusion vasodilation was inversely proportional to initial microvascular diameter.
- No significant change in microvascular diameter occurred within 2 hours of occlusion; adenosine/EDTA had no additional effect.
Conclusions:
- Coronary microvascular dilation after occlusion is inversely related to control diameter.
- Acute coronary artery occlusion abolishes pharmacologically recruitable vasodilator reserve.
- Findings contrast with responses observed after critical stenosis.
Abstract:
The exact microvascular site of coronary vasodilation after coronary artery occlusion has not been clearly established. We sought to determine 1) the microvascular site of recruitable vasodilator reserve after a critical stenosis as assessed by adenosine and EDTA, 2) the coronary microvascular site responsible for vasodilatation after total coronary artery occlusion, and 3) the microvascular site for recruitable vasodilator reserve after coronary artery occlusion as assessed by adenosine and EDTA. Hemodynamics and coronary epicardial microvascular diameter were measured in 33 dogs by means of intravital epiillumination microscopy at control conditions, during a critical stenosis, or 30, 60, and 120 min following coronary artery occlusion. To evaluate the site of pharmacologically recruitable vasodilator reserve, EDTA or adenosine was suffused onto the epicardial surface. After a critical stenosis EDTA dilated all sizes of microvessels, whereas adenosine only dilated small microvessels (less than 150 microns). After coronary artery occlusion there was vasodilation that was inversely proportional to the control microvascular diameter. Coronary microvascular diameter did not change during 2 h after coronary artery occlusion. In addition, intravenous or topically applied adenosine or topically applied EDTA had no additional effect on the coronary arteriolar diameter. We concluded that in response to sudden coronary artery occlusion, the coronary microvascular dilation was inversely related to the control microvascular diameter, and in contrast to the response after a critical stenosis, there was no pharmacologically recruitable vasodilator reserve to adenosine or EDTA following acute coronary artery occlusion.