The Role of Coronary Collaterals in Chronic Total Occlusions
Gerald S. Werner
Affiliation: Medizinische Klinik I (Cardiology & Intensive Care), Klinikum Darmstadt GmbH, Grafenstrasse 9, D- 64283 Darmstadt, Germany.
Keywords: Coronary artery disease, Stable angina pectoris, Chronic coronary occlusion, Collateral circulation.
A chronic total occlusion (CTO) describes a completely occluded coronary artery. This type of lesion is found
in about 18% of all significant lesions in patients with coronary artery disease. A system of collateral connections are observed
in almost all of these lesions, which have the capacity to prevent myocardial necrosis and may even uphold metabolic
supply to the territory distal to an occlusion to maintain full contractile capacity. During exercise these collaterals
are limited in their functional reserve, and more than 90% of patients with a well collateralized occlusion will experience
ischemia. in the absence of ideal animal models that mimic the human collateral circulation, we need to rely on studies in
man. The knowledge of collateral physiology in man has increased considerably over the past two decades with the advent
of intracoronary sensors of coronary pressure and flow velocity. A number of basic physiologic questions have been answered
by these studies. The blood supply through coronary arteries depends on a complex array of in general serial resistance
systems, with an additional array of multiple parallel resistances on the collateral level.
There seems to be a great interindividual variability in the ability to recruit preformed collateral connections in the case of
an epicardial occlusion. Collateral function can develop to a similar functional level in patients post myocardial infarction
with large akinetic territories as it does in patients with normal preserved regional function. The presence of viability is
thus not a prerequisite for collateral development. The question of practical relevance in the era of interventional therapy
of chronic occlusions is also, whether a patient with coronary artery disease will remain protected by collaterals after removing
the obstruction in the collateralized artery, or whether collaterals regress and lose their functional capacity. Both
developments are observed again mainly depending of individual predisposition.
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