Anatomy and functional significance of coronary collaterals

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Today the discussion on existence or nonexistence of coronary collaterals is historical. Collaterals can be visualized during coronary angiography as well as on postmortem studies. In the beating heart they are seen in the majority of patients with severe obstructive coronary heart disease.

The anatomical distribution is well defined. Collateral connections between right and left coronary arteries exist mainly in the area of the anterior right ventricular wall, the posterior left ventricular wall, around the apex of the heart, through the atrioventricular groove via atrial arteries, and within the intraventricular septum.

Collaterals can occur in the subepicardial, intramural, or subendocardial layers. Collaterals in the subepicardial layer show extensive variation in number and size; sometimes one single collateral vessel can measure more than 1 mm in diameter. The transseptal, intramural collaterals on the other hand are more uniform and mainly depend on anatomic variation of posterior and anterior septal branches. The subendocardial collaterals often seen in postmortem angiograms cannot be well separated angiographically (Fulton).

The functional significance of collaterals is in no doubt in clinical situations such as total occlusion of the left main coronary artery with well-conserved left ventricular function. In other situations, however, functional significance of collaterals remains questionable. The well-known relationship between severity of coronary artery disease and angiographic presence of coronary collaterals can be interpreted in different ways. The conclusion that existence of good collaterals is a sign of poor prognosis does not reflect the whole truth. From experimental studies as well as from estimation of collateral . . .



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