Pathophysiology of the Pulmonary Circulation in Emphysema Associated with Alpha ₁ Antitrypsin Deficiency

Abstract

Patients with homozygous alpha 1 antitrypsin deficiency present a unique opportunity for evaluation of the pulmonary vasculature in primary emphysema. In five patients, the detailed angiographic appearance of small (0.2-2.0 mm diameter) muscular pulmonary arteries, shown by wedge arteriography, was correlated with the results of right heart catheterization during the control hypoxemic state (average arterial P o o2 50 mm Hg), the administration of oxygen (average arterial P o o2 90 mm Hg), and a constant infusion of aminophylline. In all patients, wedge arteriograms in the lower zones of the lungs showed a sparsity of arborization and a diminished background blush of capillary filling. These abnormalities were in the areas of diminished pulmonary blood flow, as indicated by the pulmonary scintiscans and the capillary phase of pulmonary arteriograms. The administration of oxygen and of aminophylline produced an increase in the diameter of arteries 0.5 to 2 mm in diameter on the wedge arteriograms of some of the patients. The average pulmonary arterial mean pressure, 30 mm Hg, and average pulmonary vascular resistance, 300 dyne-sec-cm –5 , were both elevated during the control hypoxemic state and decreased in each patient during the administration of oxygen and of aminophylline. This study demonstrates abnormalities of the small pulmonary arteries in patients with alpha 1 antitrypsin deficiency. These abnormalities may be responsible for pulmonary hypertension and altered regional perfusion.