Myokardperfusionsuntersuchungen

Myocardial perfusion refers to the blood flow through the coronary vasculature to the heart muscle (myocardium). It provides oxygen and nutrients essential for cardiac metabolism and function. Perfusion is governed by coronary blood flow, perfusion pressure, arteriolar resistance, and the integrity of the microcirculation. A healthy heart can increase flow severalfold during stress to meet elevated metabolic demand, a phenomenon quantified as coronary flow reserve (CFR).

Physiology and determinants: At rest, myocardial perfusion is maintained within a narrow range through autoregulation. During maximal vasodilation, flow increases markedly, and CFR typically ranges from about 3 to 5 in healthy individuals. Subendocardial regions are particularly vulnerable to reduced perfusion during stress or low perfusion pressure, which can lead to ischemia if oxygen supply does not meet demand. Chronic reductions in perfusion can cause adaptive changes such as hibernation or scar formation after infarction.

Measurement and techniques: Assessing myocardial perfusion can be invasive or noninvasive. In invasive testing, coronary angiography with fractional flow reserve (FFR) evaluates the functional impact of stenosis on perfusion. Noninvasive approaches include nuclear imaging (SPECT or PET) to measure perfusion under rest and stress, perfusion magnetic resonance imaging (MRI), and perfusion computed tomography (CT). Radiotracers used in nuclear perfusion imaging include 99mTc-sestamibi, 201Tl, 13N-ammonia, and 82Rb. MRI uses gadolinium-based contrast, while CT perfusion relies on iodinated contrast.

Clinical relevance: Myocardial perfusion assessment helps diagnose ischemia due to obstructive coronary disease or microvascular dysfunction, evaluate the severity and extent of perfusion deficits, and guide management decisions such as medical therapy or revascularization. It also aids risk stratification after acute coronary events.