Thallium-201 scintigraphy at rest in ischemia and infarction

Serial imaging of the myocardium in the resting state after intravenous administration of thallium-201 can be employed to differentiate between ischemia or under-perfusion and myocardial infarction or scar. Redistribution of thallium with filling-in of defects on delayed images or rest can be observed in myocardial regions supplied by stenotic coronary arteries (greater than or equal to 70% narrowing). These myocardial segments usually exhibit normal or hypokinetic wall motion. Persistent defects over a two to three hour imaging period at rest correlate highly with Q waves on the electrocardiogram and akinetic or dyskinetic wall motion on ventriculography. Thallium scintigraphy can be successfully utilized for detecting and localizing acutely infarcted myocardium. Sensitivity for infarct detection is higher in the first 24 hours after the onset of chest pain, although with computer-assisted quantitative analysis of images sensitivity for late detection (ten to fourteen days post myocardial infarction) may be improved. Multivessel disease can be predicted in many patients with acute inferior myocardial infarction by demonstrating anteroseptal wall defects with delayed redistribution on rest images prior to hospital discharge. Patients who demonstrate inferior wall persistent defects (infarction) with anterior wall redistribution (hypoperfusion/ischemia) have a worse prognosis characterized by an increased frequency of recurrent angina and infarction compared to the group with only inferior defects. Thallium scintigraphy may also be useful in assessing myocardial infarct size. Patients with large defects during the acute phase of infarction have significantly higher early and late mortality.