Myocardial Flow Reserve (MFR) Calculator

Myocardial Flow Reserve (MFR): Explanation and Clinical Context Myocardial Flow Reserve (MFR) is a quantitative index derived from positron emission tomography (PET) myocardial perfusion imaging, calculated as the ratio of hyperemic (stress) myocardial blood flow (MBF) to resting MBF. An MFR value below 2.0 is considered abnormal and reflects impaired coronary vasodilator capacity, which may result from epicardial coronary artery stenosis, microvascular dysfunction, or diffuse atherosclerotic disease. MFR provides incremental prognostic information beyond perfusion defects alone, correlating with all-cause mortality, major adverse cardiovascular events (MACE), and outcomes in both obstructive and non-obstructive coronary artery disease.

Patients with MFR < 2.0 have been shown to have a two- to four-fold higher risk of cardiac death or myocardial infarction compared with those with preserved MFR (≥2.0). Quantitative PET MFR analysis thus represents a robust, reproducible, and non-invasive method for assessing coronary vascular health, integrating both macrovascular and microvascular components of coronary flow regulation.