Myocardial visualization on a routine perfusion lung scintigram: relationship to the amount of right-to-left shunt.

Three cases of myocardial visualization on a routine perfusion lung scintigram with 99mTc-macroaggregated albumin were reported in patients with congenital heart diseases; two cases of tetralogy of Fallot and one case of truncus arteriosus type IV. Large right-to-left shunts greater than 39% and marked hypertrophy of the ventricle suggesting the presence of increased coronary blood flow were noted in all cases. In the two patients with tetralogy of Fallot myocardial activity appeared to be located in the hypertrophic right ventricles.