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An association between collateral blood flow and myocardial viability in patients with recent myocardial infarction
P J Sabia1, E R Powers, M Ragosta
1Department of Medicine, University of Virginia School of Medicine, Charlottesville 22908.
Insights
Successful reperfusion of blocked arteries after myocardial infarction improves heart function, especially when collateral blood flow is present in the infarct area. This indicates preserved heart muscle viability.
Area of Science:
- Cardiology
- Interventional Cardiology
- Echocardiography
Background:
- Acute myocardial infarction (MI) can lead to prolonged occlusion of infarct-related coronary arteries.
- Regional wall motion abnormalities are a common consequence of MI.
- The role of collateral circulation in preserving myocardial function post-MI requires further investigation.
Purpose of the Study:
- To investigate the impact of late reperfusion on regional wall motion after acute myocardial infarction.
- To determine the relationship between collateral blood flow and functional recovery in the infarct zone.
- To assess the viability of myocardium in patients with occluded infarct-related arteries.
Main Methods:
- Two-dimensional echocardiography was used to assess regional wall motion at baseline and one month post-angioplasty.
- A five-point wall-motion score was assigned to evaluate cardiac function.
- Myocardial contrast echocardiography quantified collateral blood flow percentage within the infarct bed.
Main Results:
- Successful angioplasty in 32 patients significantly improved wall motion compared to 9 unsuccessful cases (78% vs 11% improvement).
- Collateral flow percentage positively correlated with wall function and inversely with wall-motion score post-angioplasty (r = -0.64, P < 0.001).
- Patients with >50% collateral flow showed significantly better wall motion and improvement than those with <=50% collateral flow.
Conclusions:
- Myocardium remains viable for extended periods after acute myocardial infarction with occluded arteries.
- Collateral blood flow within the infarct bed is a key factor associated with myocardial viability.
- Late reperfusion strategies may improve cardiac function in selected MI patients.
Background:
We hypothesized that successful reperfusion of an occluded infarct-related coronary artery even late after acute myocardial infarction would result in improved regional wall motion and that such improvement might be related to the presence of collateral blood flow within the infarct bed.
Methods:
We assessed regional wall motion by two-dimensional echocardiography at base line and one month after angioplasty was attempted in the occluded infarct-related artery in 43 patients who had had a myocardial infarction two days to five weeks earlier. A wall-motion score was assigned to each patient on a five-point scale (from 1 [normal function] to 5 [dyskinesia]). The percentage of the infarct bed perfused by collateral flow was assessed with myocardial contrast echocardiography.
Results:
In the 41 patients who had abnormal wall motion at base line, improvement in function was noted in 25 (78 percent) of the 32 in whom angioplasty was successful, as compared with only 1 (11 percent) of the 9 in whom it was unsuccessful (P < 0.001). The percentage of the infarct bed supplied by collateral flow at base line was directly correlated with wall function and inversely correlated with the wall-motion score one month after successful angioplasty (r = -0.64, P < 0.001). Among the patients in whom angioplasty was successful, the 23 in whom > 50 percent of the infarct bed was supplied by collateral flow had better wall motion (P < 0.001) and greater improvement in wall motion at one month (P = 0.004) than the 9 in whom < or = 50 percent of the bed was supplied by collateral flow. The degree of improvement in function was not influenced by the length of time between the infarction and the attempted angioplasty.
Conclusions:
The myocardium remains viable for a prolonged period in many patients with acute infarction and an occluded infarct-related artery. Viability appears to be associated with the presence of collateral blood flow within the infarct bed.