Multifactorial determination of 201thallium uptake of the heart: an experimental study concerning the influence of ventricular mass, perfusion and oxygen consumption.

Studies were performed in 42 cats in order to analyze the determinants of myocardial 201Thallium uptake. (1) Ventricular mass represents the major determinant of myocardial 201Thallium uptake. The inner (subendocardial) layer of the left ventricle storages 10-15 per cent more Thallium than the outer (subepicardial) layer, whereas the right ventricle has 201Thallium accumulation by 40 per cent less than the left ventricle. (2) Coronary perfusion increase as induced by intravenous injection of dipyridamole leads-at constant muscle mass-to considerable increase in myocardial 201Thallium uptake by 106 per cent. (3) Changes in myocardial oxygen consumption as induced by inotropic interventions are associated with considerable changes in the myocardial 201Thallium uptake. These results demonstrate that ventricular mass, myocardial flow and myocardial oxygen consumption are major determinants of myocardial 201Thallium uptake. Thus, by quantitiative determination of the myocardial 201Thallium uptake, a useful equivalent of the viability degree of the left ventricle, which itself is determined by mass, flow and metabolism, may be obtained.