Isotope methods of determination of myocardial viability.

The decision to perform myocardial revascularization in patients with chronic ischaemic heart disease or following infarction, is based on many criteria such as coronary anatomy, left ventricular function, the clinical context and the patient's physiological age. It is also essential to confirm the presence of ischaemic but viable myocardium in the territory concerned by the revascularization. Functional imaging techniques allow the demonstration of this hibernating myocardium: thallium 201 myocardial tomoscintigraphy provides the clinician with a reliable answer in the great majority of cases. A number of examination protocols have been developed in order to make this investigation more efficient: late films, reinjection, etc. New tracers of viability are also currently under evaluation. Positon emission tomography (PET) is currently considered to be the reference technique for the detection of viable myocardium. Numerous tracers are used and this technique allows parallel evaluation of cellular metabolism and myocardial perfusion. Unfortunately, this type of investigation is expensive and not widely available. The use of positon emitter isotopes with conventional cameras appears to give encouraging results. Finally, among the other functional imaging devices, stress ultrasonography gives good results in the detection of hibernating myocardium. Contrast ultrasonography and magnetic resonance imaging are currently under development.