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Contrast echocardiographic mapping of collateralized myocardium in humans before and after coronary angioplasty
H P Grill1, J A Brinker, J C Taube
1Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Insights
Contrast echocardiography effectively maps myocardial perfusion from coronary collateral vessels. This technique accurately identifies collateralized heart muscle and quanties changes after interventions like angioplasty.
Area of Science:
- Cardiovascular Imaging
- Interventional Cardiology
- Myocardial Perfusion Imaging
Background:
- Coronary collateral vessels provide alternative blood flow but their myocardial territory is not well-defined by conventional arteriography.
- Identifying collateralized myocardium is crucial for understanding myocardial viability and treatment response.
Purpose of the Study:
- To evaluate the efficacy of contrast echocardiography in mapping collateralized myocardium.
- To compare perfusion maps in patients with and without angiographic collateral flow before and after angioplasty.
Main Methods:
- Contrast echocardiography with separate injections into coronary arteries to create perfusion maps.
- Computerized analysis to quantify overlapping perfusion areas (collateralized myocardium) relative to total myocardial area and recipient vessel area.
- Comparison of perfusion maps in patients with and without angiographic collateral flow, and after angioplasty.
Main Results:
- Patients with angiographic collateral flow showed significantly larger overlap areas (30.6% of total myocardium, 89.2% of recipient vessel area) compared to those without (1.3%, 6.6%; p<0.001).
- Following angioplasty that abolished collateral flow, overlap area significantly decreased (p<0.05).
Conclusions:
- Contrast echocardiography accurately maps the specific myocardial territory supplied by coronary collateral flow.
- This technique can document immediate changes in collateral perfusion following interventions.
Abstract:
Conventional coronary arteriography is able to demonstrate the presence of coronary collateral vessels but cannot delineate the specific region of myocardium to which they supply blood. To test the hypothesis that contrast echocardiography can specifically identify collateralized myocardium, contrast echocardiographic perfusion "maps" were compared in patients with (n = 12) and without (n = 12) angiographic evidence of coronary collateral flow, both before and after coronary angioplasty. Contrast echocardiographic images of the mid-left ventricle in the short-axis view at end-diastole were obtained after separate injections of a sonicated contrast agent into both the right and the left coronary arteries. A computer-based contouring system was used to determine the individual areas of myocardium perfused by each of the two coronary arteries and then to superimpose the images of the two perfusion beds. The resulting area of overlapping perfusion represented myocardium receiving blood flow from both coronary systems and was defined as collateralized myocardium. To normalize for heart size, overlap area was expressed as a percent of total myocardial area, which was the area between endocardium and epicardium in the short-axis view. To adjust for differences in vascular distribution, overlap area was expressed as a percent of the perfusion area of the recipient vessel. In patients with angiographic collateral flow, the recipient vessel was that vessel receiving the collateral flow. In patients without angiographic collateral flow, the right coronary artery was considered the recipient vessel. Overlap area was 1.3 +/- 0.4% of total myocardial area and 6.6 +/- 1.7% of recipient vessel area in patients without angiographic evidence of collateral flow compared with 30.6 +/- 2.5% and 89.2 +/- 6.4%, respectively, in patients with angiographic collateral flow (p less than 0.001 for both). In four patients in whom angiographic collateral flow was abolished by angioplasty, overlap area decreased from 30.3 +/- 5.3% to 6.8 +/- 2.7% of total myocardial area and from 100% to 18.5 +/- 5.4% of recipient vessel area (p less than 0.05 for both). Thus, contrast echocardiography is able to map the specific myocardial territory perfused by coronary collateral flow and document an immediate reduction in perfusion in this territory when collateral flow is abolished by angioplasty.