Korean Circ J.  2015 Sep;45(5):351-356. 10.4070/kcj.2015.45.5.351.

Assessment of Myocardial Collateral Blood Flow with Contrast Echocardiography

• Kaul S

• KMID: 2223796
• DOI: http://doi.org/10.4070/kcj.2015.45.5.351

Abstract

Humans have pre-formed collateral vessels that enlarge with ischemia. In addition, new vessels can be formed within ischemic zones from pre-formed endocardial arcades of vessels providing rich collateral flow. Collateral flow under resting conditions (if >25% of normal) is enough to maintain myocardial viability, but may be insufficient to prevent myocardial ischemia under stress. Coronary angiography is a poor tool for collateral flow assessment. Myocardial contrast echocardiography is arguably the gold standard for experimental and clinical measurement of collateral flow. This review describes several experimental and clinical studies that highlight the importance of the collateral circulation in coronary artery disease.

Keyword

Collateral blood circulation; Contrast echocardiography; Myocardial ischemia

MeSH Terms

Collateral Circulation
Coronary Angiography
Coronary Artery Disease
Echocardiography*
Humans
Ischemia
Myocardial Ischemia

Figure

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  Fig. 1 Post-mortem high-resolution angiogram of a thin transverse section of the heart of a 29 year old normal individual. Note pre-existing collaterals between anterior and posterior circulations, as well as the endocardial arcades formed by the penetrating arteries. From Gross and Kugel,2) with permission from C.V. Mosby Company.

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  Fig. 2 Post-mortem high-resolution angiogram of a thin transverse section of the heart of an older male with left anterior descending artery occlusion, demonstrating abundant collateral vessel development within the LAD bed to circumvent infarction despite the occluded vessel. Compare with Fig. 1. From Fulton et al,3) with permission of the British Medical Association. R: right, L: left, RC: right coronary artery, LC: left circulatory artery, LCxA; left circumflex artery, ANT: left anterior descending artery, ADA: anterior diagonal artery.

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  Fig. 3 Short-axis echocardiographic view of a patient with a totally occluded right coronary artery after acute myocardial infarction taken in the cardiac catheterization laboratory. A depicts a MCE image after microbubble injection into the left main coronary artery showing contrast enhancement of the entire left ventricular myocardium. B depicts the same view after successful angioplasty of the right coronary artery and direct injection of microbubbles, showing the perfusion bed of the right coronary artery. At the time of coronary occlusion, this bed was supplied by collaterals from the left system (top panel). From Sabia et al,9) with permission of the New England Medical Society. MCE: myocardial contrast echocardiography, RV: right ventricle, LV: left ventricle.

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  Fig. 4 Method of measuring myocardial blood flow using MCE. A shows the ultrasound beam elevation (thickness) represented as 'E' in a. If all the microbubbles in the elevation are destroyed by a single pulse of ultrasound at t0, then replenishment of the beam elevation (d1-d4, b-e), will depend on the velocity of microbubbles and time of imaging. B shows the pulsing interval (x-axis) versus video-intensity (y-axis) plot where myocardial blood volume is shown as A and rate of microbubble replenishment is shown as β. The function used to fit the relation is also depicted. Adapted from Wei et al,18) with permission of the American Heart Association. MCE: myocardial contrast echocardiography.

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  Fig. 5 Perfusion defect size at various times after bubble destruction and final infarct size (by tissue staining) in a dog undergoing 6 hours of left circumflex artery occlusion. In this example, although risk area is large (A), the infarct size is small and located at the tip of the posteromedial papillary muscle (C). This is the only region showing a perfusion defect at 10.7s when collaterals have filled the rest of the risk area (B). Adapted from Coggins et al.21) with permission of the American Heart Association.

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  Fig. 6 Perfusion defect sizes at various times after bubble destruction and final infarct size (by tissue staining) in a dog undergoing 6 hours of left circumflex artery occlusion. In this example, although the risk area (A) is the same size as in Fig. 5, the infarct size is much larger (C) because of less collateral-derived flow. The region that became infarcted has no opacification at 9.2 s. (B) Adapted from Coggins et al.21) with permission of the American Heart Association.

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  Fig. 7 Images from a dog undergoing 6 hours of left anterior descending artery occlusion with a large MCE defined risk area (A), confirmed by radiolabeled microspheres (B). The risk area is mostly filled with collateral flow several seconds later (C) resulting in a very small infarct (D). The rest of the risk area is supplied by collateral flow that is lower than in the normal remote myocardium. Thus, the circumferential extent of abnormal wall thickening was greater than the circumferential extent of infarction. MCE: myocardial contrast echocardiography.

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  Fig. 8 Flow-function relation in dogs undergoing 6 hours of total coronary occlusion. The data points in red denote the infarcted zone, those in green denote the collateralized zone, and those in blue denote the normal myocardium. All data points fall on the same line. See text for details. From Leong-Poi et al.27) with permission of the American Heart Association. WT: wall thickening, MBF: myocardial blood flow.

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  Fig. 9 Images from a dog with a non-critical single vessel left circumflex artery stenosis at peak Dobutamine dose with a large MCE-defined risk area (A) that is similar in topology to hypo-perfused zone by radiolabeled microspheres (B). The risk area is almost completely filled by collateral flow a few seconds after microbubble destruction (except for area shown by yellow arrows) (C), resulting in minimal systolic wall thickening abnormality seen on echocardiography (except for area shown by yellow arrows) (D). From Leong-Poi et al.27) with permission of the American Heart Association. MCE: myocardial contrast echocardiography.

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  Fig. 10 Flow-function relation in dogs with non-critical single-vessel stenosis undergoing Dobutamine stress echocardiography. The data points in red denote the central portion of the perfusion defect on MCE. The data points in green are from the intermediate zone within the perfusion defect that fills with collateral flow. The data points in blue denote the remote normal myocardium. All data points fit the same curvilinear relation. At above hyperemic flows of 2-3 mL.min.g-1, wall thickening no longer increases with increase in flow. Thus, wall thickening measures during stress is not as sensitive as blood flow measurement for detection of coronary artery stenosis. See text for details. From Leong-Poi et al.27) with permission of the American Heart Association. WT: wall thickening, MBF: myocardial blood flow.

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