Dr. Marco Zimarino
Coronary collateral circulation offers an alternative source of blood supply to the myocardium when the original vessel fails to provide sufficient blood flow. The recent concern for late thrombotic occlusion after percutaneous coronary interventions (PCI) with drug-eluting stents (DES) has stimulated the interest in the protective effect of collateral circulation. In this view, the session “Collateral circulation: from bench to bedside” which I had the honour to co-chair with Bernard De Bruyne (Aalst, BE), was extremely interesting.
Wolfgang Schaper (Bad Nauheim, DE) elucidated the pathophysiology of collateral circulation. He pointed out that shear stress, more than myocardial ischemia, is the major force that activates endothelium and promotes the "cascade" for collateral formation. Pim De Feyter (Rotterdam, NL) illustrated how the newest miniaturized systems overcame contrast angiography and allowed an extremely detailed monitoring of coronary blood flow and pressure in humans. Collateral circulation needs 4 to 12 weeks to develop; once established, it is however far from being immutable and steadily present to promptly support myocardial territories forever. As clearly presented by Christian Seiler (Bern, CH) and then by Gerald Werner (Darmstadt, DE), the behaviour and the functional relevance of collaterals is extremely variable. After successful PCI of a chronic total occlusion, with the re-establishment of antegrade flow, collaterals show a rapid regression. Moreover the viability of the myocardium, comorbidities (e.g. diabetes), disease of the donor artery and the drug eluting from the stent platform may all impair collateral function and even cause collateral "steal"; such changes expose the patients to a higher risk of future ischemic events in the case of vessel re-occlusion.
The knowledge of collateral behaviour is relevant for the management of patients with coronary artery disease and the selection of candidates for PCI. After the successful recanalization of a chronic total occlusion, all possible strategies, including device selection, optimal stent deployment and pharmacological strategies (aggressive and prolonged antiplatelet therapy) should be recommended to prevent reocclusion.
Collateral circulation: from bench to bedside Basic Science Track
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