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Variability of myocardium at risk for acute myocardial infarction
K W Klarich1, T F Christian, S T Higano
1Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Insights
Myocardium at risk for infarction varies significantly based on the infarct-related artery and occlusion location. Proximal occlusions and reduced Thrombolysis In Myocardial Infarction (TIMI) flow increase infarct size.
Area of Science:
- Cardiology
- Radiology
- Medical Imaging
Background:
- Assessing myocardium at risk is crucial for acute myocardial infarction management.
- Variability in infarct size necessitates understanding contributing factors.
- Coronary angiographic features are key determinants of infarct-related artery characteristics.
Purpose of the Study:
- To quantify myocardial perfusion defects and assess variability in myocardium at risk.
- To correlate the extent of myocardium at risk with coronary angiographic variables.
- To identify predictors of infarct size in patients with ST-segment elevation myocardial infarction.
Main Methods:
- 197 patients with ST-segment elevation myocardial infarction received technetium-99m sestamibi before reperfusion therapy.
- Myocardium at risk was quantified by perfusion defect size.
- Coronary angiography assessed infarct-related artery, occlusion location, collateral, and TIMI flow.
Main Results:
- Myocardium at risk was largest in the left anterior descending coronary artery distribution, especially with proximal occlusions (p <0.0001).
- A trend for larger myocardium at risk with proximal occlusions was observed in the left circumflex (p = 0.14), but not the right coronary artery (p = 0.47).
- Infarct-related artery, TIMI flow, and proximal occlusion location independently predicted myocardium at risk (p <0.0001, p = 0.0002, p = 0.09 respectively).
Conclusions:
- Infarct-related artery, TIMI flow, and proximal occlusion location significantly influence the myocardium at risk.
- Myocardium at risk exhibits considerable variability even for a given occlusion location.
- These findings highlight the importance of angiographic assessment in predicting infarct size.
Abstract:
The objective of this study was to assess the variability in myocardium at risk and relate this to coronary angiographic variables. One hundred ninety-seven patients with > or = 1-mm ST-segment elevation in 2 contiguous electrocardiographic leads, without prior myocardial infarction, were injected with technetium-99m sestamibi acutely before reperfusion therapy. The perfusion defect was quantified to determine myocardium at risk for infarction. Patients underwent coronary angiography to determine the infarct-related artery and to classify the occlusion as proximal or not proximal. Collateral and anterograde (Thrombolysis In Myocardial Infarction [TIMI] trial) flow were assessed in a subset of 83 patients with angiography before direct angioplasty. Myocardium at risk for infarction in the distribution of the left anterior descending coronary artery was significantly greater (p <0.0001) than that in the circumflex or right coronary artery. In the left anterior descending coronary artery distribution, myocardium at risk for infarction was significantly larger for proximal occlusions (p <0.0001). There was a trend toward greater myocardium at risk for infarction of proximal occlusions (p = 0.14) of the left circumflex but not for proximal occlusions in the right coronary artery distribution (p = 0.47). Multivariate analysis revealed that the infarct-related artery (p <0.0001), TIMI flow (p = 0.0002), and proximal location (p = 0.09) in the infarct-related artery were independent predictors of myocardium at risk for infarction. Thus, infarct-related artery, TIMI flow, and proximal location of occlusion in the infarct-related artery influence the myocardium at risk for infarction, which is highly variable for given location of occlusion.