Abstract
Studies performed in the last two decades demonstrate that after successful percutaneous coronary intervention (PCI) of a chronically occluded coronary artery, the physiology of the chronic total occlusion (CTO) vessel and dependent microvasculature does not normalise immediately but improves significantly over time. Generally, there is an increase in fractional flow reserve (FFR) in the CTO artery, a decrease in collateral blood supply and an increase in FFR in the donor artery accompanied by an increase in blood flow and decrease in microvascular resistance in the myocardium supplied by the CTO vessel. Analogous to these physiological changes, positive remodelling of the distal CTO artery also occurs over time, and intravascular imaging can be helpful for analysing distal vessel parameters. Follow-up coronary angiography with physiological measurements after several weeks to months can be helpful and informative in a subset of patients in order to decide upon the necessity for treatment of residual coronary artery stenosis in the vessel distal to the CTO or in the contralateral donor artery, as well as in deciding whether stent optimisation is indicated. We suggest that such physiological guidance of CTO procedures avoids unnecessary overtreatment during the initial procedure, guides interventions at follow-up, and improves our understanding of what PCI in CTO means.
Highlights
To answer the question as to what coronary physiology teaches us during and after percutaneous coronary intervention (PCI) of chronic total occlusion (CTO), it is important to emphasise that interventional treatment should be based upon knowledge and understanding of the underlying pathophysiology
Why does a patient suddenly present with angina caused by a CTO that has existed for years? How does a stenosis in the donor artery influence CTO blood supply? What kind of improvement can be expected following PCI?
In most CTOs with viable distal myocardium, collateral blood supply is present and sufficient to maintain resting metabolism or even contraction at rest. This collateral circulation generally develops over several weeks to months and the extent of the collateral network depends on the acuity of the occlusion, the duration and frequency of ischaemia, genetic influence and co-morbid states, e.g. diabetes [3]
Summary
To answer the question as to what coronary physiology teaches us during and after percutaneous coronary intervention (PCI) of chronic total occlusion (CTO), it is important to emphasise that interventional treatment should be based upon knowledge and understanding of the underlying pathophysiology. In most CTOs with viable distal myocardium, collateral blood supply is present and sufficient to maintain resting metabolism (hibernation) or even contraction at rest. This collateral circulation generally develops over several weeks to months and the extent of the collateral network depends on the acuity of the occlusion, the duration and frequency of ischaemia, genetic influence and co-morbid states, e.g. diabetes [3]. In cases of regional wall motion abnormalities in the territory of the CTO, other objective evidence of viability should be sought before making the decision to perform PCI [6]. Physiological measurements in the recanalised CTO artery, its dependent myocardium and donor artery may be helpful in optimising the procedure and might improve longterm clinical outcomes
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