While fractional flow reserve (FFR) is a good diagnostic index to assess the myocardial ischemia, coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) can be used to address microvascular status without any significant epicardial disease. The independent predictors for FFR and IMR are totally different and acts differently on the macro- and micro-vascular dysfunction. In high FFR patients, low CFR and high IMR which indicates the presence of overt microvascular disease demonstrated poor prognosis. Thus, comprehensive physiological assessments using FFR, CFR and IMR could improve the ability to discriminate patients at high risk of future events.
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