Alterations in Regional Pulmonary Blood Flow in Mitral Valve Disease Studied by Radioisotope Scanning

Abstract

The distribution of pulmonary blood flow was studied by external scintillation scanning of intravenously injected ¹³¹I-labeled macroaggregates of human serum albumin. The technique, its validation, and the underlying considerations are discussed in detail. In 13 normal subjects, in whom the indicator was injected while they were in the erect position, the ratio of concentration of radioactivity per unit of lung volume in the upper third of the right lung to that in the lower third (U/L) averaged 0.43±0.08 sd. When ¹³¹I-MAA was injected with the subjects in the supine position, this ratio averaged 0.92±0.05. In 35 patients with mitral valve disease in whom the injections were made while they were in the erect position, varying abnormalities of the distribution of the pulmonary arterial blood flow were observed, U/L averaging 1.01±0.34. The extent of the abnormality of distribution was found to be a function of the hemodynamic severity of the mitral valve disease, and U/L correlated more closely with the mean left atrial pressure than with any other hemodynamic variable. The potential applicability of the ¹³¹I-MAA technique in the detection and assessment of mitral valve disease was discussed.