Perfusion and ventilation radioisotope lung scans in stenosis of the pulmonary arteries and their branches

Abstract

In ten patients with stenosis of the pulmonary arteries, the relative distribution of right and left pulmonary blood flow was related to the localization of the coarctation by angiography and the degree of stenosis. To evaluate the distribution of pulmonary blood flow, the scintillation lung scan after injection of 131I macroaggregated albumin (MAA) was utilized. Scintillation scanning of the lungs after inhalation of xenon-133 gas was also performed to assess the distribution of ventilation. The relative right to left pulmonary arterial blood flow distribution showed a good correlation with the catheterization pressure gradients and the angiographic findings. The distribution of ventilation was relatively unaffected. In a patient with a precordial murmur that exhibits disproportionate radiation to the axilla and back, an altered distribution of right to left perfusion helps to substantiate the diagnosis of stenosis of the pulmonary arteries. However, if the obstruction is bilateral and of equal degree, the distribution of blood flow may be normal. In patients with isolated acyanotic left to right shunts, the right to left distribution of pulmonary blood flow is apparently unaltered so that a lateral shift from the normal pattern raises the question of stenosis of the pulmonary arteries as an additional lesion. The finding of patchy areas of decreased radioactivity in both perfusion and ventilation lung scans in four of ten patients suggest that there may be a high incidence of emphysema or other lung disease in these patients.