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Myocardial perfusion refers to the flow of blood through the heart muscle (myocardium) delivered by the coronary arteries. Adequate perfusion supplies oxygen and nutrients needed for contraction and metabolism. Regional myocardial blood flow is typically expressed as milliliters per minute per gram of tissue and is governed by coronary driving pressure and microvascular resistance. The heart increases flow during stress or exercise through vasodilation and redistribution of blood to areas with higher metabolic demand.

Perfusion is assessed at rest and under stress to reveal areas with reduced blood flow. In health, perfusion matches myocardial demand. In disease, especially coronary artery disease, flow-limiting stenoses or microvascular dysfunction can create perfusion defects that indicate ischemia or determine the extent of viable tissue. Absolute flow measurements can be obtained with certain imaging techniques, aiding risk stratification and treatment planning.

Imaging modalities used to evaluate myocardial perfusion include nuclear medicine techniques such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET), which use various tracers to map blood flow. Cardiac magnetic resonance (MRI) perfusion imaging with gadolinium provides high spatial resolution without ionizing radiation. Computed tomography (CT) perfusion and other advanced methods are also used in some settings. These tools help distinguish reversible ischemia from scar and guide management decisions, including medical therapy, percutaneous or surgical revascularization, and prognosis.

Limitations of perfusion imaging include artifacts from technical factors, attenuation, and, in some cases, balanced ischemia where defects are not readily apparent. Radiation exposure and contrast risks may apply to certain modalities.