Assessment of viability after myocardial infarction. Clinical relevance and methodological problems.

In patients with myocardial infarction, the distinction between reversible and irreversible ventricular dysfunction has important clinical implications since dysfunctional but viable myocardium will resume contraction following revascularization. Various methods have been developed for the identification of potentially reversible myocardial dysfunction. Thallium reinjection, immediately after stress-redistribution imaging, may provide evidence of myocardial viability by demonstrating thallium uptake in regions with apparently 'irreversible' defects. Hypoperfused, hypocontractile segments may recover function after revascularization, when exhibiting increased 18F-fluoro-deoxy-glucose uptake on positron emission tomography. Improved contractile function by selective beta 1 adrenergic stimulation with low dose dobutamine may also indicate the presence of viable tissue and predict subsequent improvement upon restoration of adequate flow. Finally, exercise-induced ST segment elevation on leads exploring a recent myocardial infarction has also been shown to indicate the presence of viable, potentially salvageable tissue. We discuss here these and several other methods that have been proposed for the detection of residual myocardial viability. Their advantages, limitations, and relevance to clinical problems are also discussed.