ISOTOPE METHODS OF DETERMINATION OF MYOCA RDIAL VIABILITY

The decision to perform myocardial revascularization in patients with chronic ischaemic heart disease or following infarction, is based on m any criteria such as coronary anatomy, left ventricular function, the clinical context and the patient's physiological age. It is also essen tial to confirm the presence of ischaemic but viable myocardium in the territory concerned by the revascularization. Functional imaging tech niques allow the demonstration of this hibernating myocardium: thalliu m 201 myocardial tomoscintigraphy provides the clinician with a reliab le answer in the great majority of cases. A number of examination prot ocols have been developed in order to make this investigation more eff icient: late films, reinjection, etc. New tracers of viability are als o currently under evaluation. Positon emission tomography (PET) is cur rently considered to be the reference technique for the detection of v iable myocardium. Numerous tracers are used and this technique allows parallel evaluation of cellular metabolism and myocardial perfusion. U nfortunately, this type of investigation is expensive and not widely a vailable. The use of positon emitter isotopes with conventional camera s appears to give encouraging results. Finally, among the other functi onal imaging devices, stress ultrasonography gives good results in the detection of hibernating myocardium. Contrast ultrasonography and mag netic resonance imaging are currently under development.