Abstract
A 34 mo. old child with tetralogy of Fallot developed an acute, primary thrombosis of the pulmonary trunk. A greatly increased hematocrit was most probably a predisposing factor. An unusual postmortem finding was the large number of extremely dilated myocardial capillaries. In a review of a series of 394 consecutive necropsy cases with many kinds of cardiac anomalies, there was only 1 case (a 28 yr old man) with occluding thrombus formation in the pulmonary artery. This case belonged to the Fallot group but a subacute glomerulonephritis seemed to be the major cause of death.