Regional myocardial perfusion abnormalities: Fractional flow reserve versus cardiac magnetic resonance first-pass perfusion imaging

Identification of the functional severity of intermediate coronary artery lesions is challenging for the interventional cardiologist. Functional severity can be measured invasively using the fractional flow reserve (FFR). However, FFR has the disadvantage of being invasive and associated with radiation exposure. Cardiac MRI (CMR) offers the opportunity to assess myocardial perfusion noninvasively. A semiquantitative index of myocardial perfusion (perfusion reserve index or PRI) can be obtained from the first-pass of a bolus of gadolinium through the myocardium. Studies comparing the invasive FFR to CMR perfusion imaging in patients with coronary artery stenosis of undefined significance have demonstrated that CMR first-pass perfusion imaging may be useful for the assessment of their functional significance. However, in patients with a high prevalence of microvascular dysfunction, the value of this method may be limited because the PRI may be influenced by both the epicardial conductance vessel function as well as microvascular function.