myokardperfusion

Myocardial perfusion refers to the flow of blood through the coronary circulation to the heart muscle (myocardium), delivering oxygen and nutrients needed for contraction and metabolism. Perfusion is governed by coronary blood flow, perfusion pressure, and the balance between myocardial oxygen demand and supply. Under normal conditions the heart regulates flow to meet demand, with the subendocardial regions being particularly sensitive to supply shortfalls.

Physiology and assessment of perfusion focus on detecting regional differences in blood flow. Adequate perfusion depends on intact coronary arteries and microvasculature, as well as factors such as heart rate, blood pressure, and myocardial workload. Perfusion can become impaired during stress or exertion when demand increases or when supply is limited by obstructive or microvascular disease, producing ischemic symptoms or detectable abnormalities on imaging.

Imaging techniques for myocardial perfusion include noninvasive methods such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET). SPECT uses radiotracers like technetium-99m or thallium-201, while PET employs tracers such as rubidium-82 or ammonia to quantify regional blood flow. Cardiac magnetic resonance (CMR) perfusion and CT perfusion are alternative modalities. Invasive assessment may involve hemodynamic measurements and functional tests, such as fractional flow reserve, to infer perfusion impact of coronary lesions.

Interpretation centers on identifying reversible defects, which suggest inducible ischemia due to significant coronary narrowing, versus fixed defects, which indicate scar or infarct. Additional quantitative metrics from PET, such as myocardial blood flow and myocardial flow reserve, provide objective measures of perfusion. Myocardial perfusion testing informs diagnosis, risk stratification, and treatment planning for coronary artery disease. Limitations include modality-specific artifacts, availability, cost, and radiation exposure in some tests.