Alterations in pulmonary blood flow distribution in heart diseases with pulmonary hypertension studies by radioisotope (131-I-MAA) scanning.

Utilizing the 1311-MAA (macroaggregated albumin labeled with iodine-131) scintillation scanning method, regional pulmonary blood flow distribution was studied in 47 cardiac patients with pulmonary hypertension. Remarkable increase of blood flow in the upper zones of the lung together with decrease in the lower zones was found in the majority of the patients with mitral valve disease, while in the congenital heart disease with left to right shunt group, elevation of upper/lower ratio of pulmonary blood flow was minimal even in the patients with severe pulmonary hypertension. Upper/lower ratio of pulmonary blood flow showed a good correlation with left atrial pressure and mean pulmonary circulation time but not with pulmonary arterial pressure. The mechanism underlying these differences of pulmonary circulation pattern in various heart diseases with pulmonary hypertension was discussed and the role of primary factors (perivascular edema and vasoconstriction) was emphasized as the cause of this reversed pattern of pulmonary circulation. Postoperative studies on the 16 patients with mitral valve disease proved that this abnormal distribution of pulmonary blood flow could be improved in a comparatively short time by successful surgical correction of the disease, whereas in those patients with upper/lower blood flow ratio in an erect position over 2.0, high operative mortality resulted. The surgical significance of the upper/lower pulmonary blood flow ratio measurment in determining the operative risk and curability of the disease was also discussed.