ASSESSING VIABLE MYOCARDIUM WITH TL-201

Patients with chronic coronary artery diseaese and potentially reversible left ventricular dysfunction can often be successfully identified by one or mom clinical indicators af myocardial viability, including regional wall motion, systolic wall thickening, regional myocardial perfusion as determined by perfusion tracers, and redistribution af thallium-201. In some patients, however, viable but "hibernating" myocardium will exist even when none of the above are evident. Myocardial viability in this situation can be detected with a high degree af accuracy by the demonstration of preserved metabolic activity by positron emission tomography (PET) scanning, Additionally, modifications af the standard exercise-redistribution thallium protocol may also produce accurate results. These modifications include late thallium-201 redistribution imaging, performed 8-72 hours following initial thallium injection, and thallium reinjection at rest after early (3-4 hours) or late (8=72 hours) redistribution imaging. These methods can identify viable myocardium in many thallium defects that appear to be irreversible on a standard 3-4 hour redistribution image. In addition, serial imaging after administration of thallium-201 at rest may also provide valuable insights into myocardial viability. These imaging modalities have important practical applications in the evaluation and management af patients with coronary artery disease and left ventricular dysfunction.