Aorta-pulmonary shunts in growing pigs. Functional and structural assessment of the changes in the pulmonary circulation.

Aorta-pulmonary shunts were produced in growing pigs, 4 to 12 weeks of age, by anastomosing the thoracic descending aorta to the pulmonary trunk, and the animals were followed for periods of 1 to 3 months. Correlation between the hemodynamic findings and the lung structure, analyzed by quantitative methods, showed that the young group (operated upon at 4 weeks of age) developed more severe pulmonary hypertension with increased muscularization of arteries of all sizes and reduction in the size of those running with respiratory bronchioli and beyond. Since this response is similar to that seen in cases of left-to-right shunt associated with congenital heart defects and pulmonary hypertension early in life, it seems that the present experiments reproduce the early response of the growing lung to such hemodynamic disturbance.