Artificially produced pulmonary artery stenosis in the dog

The genesis of the obstructive infundibular hypertrophy which is seen in association with pulmonary valvar stenosis, especially beyond infancy, has been explained upon an acquired basis (compensatory) but this has not been substantiated. Also, there are conflicting opinions about the necessity for resecting the infundibular muscle when the pulmonary valve is lysed. Experiments were devised using puppies in which the main pulmonary artery was banded. There was progressive increase in the right ventricular pressure, marked infundibular hypertrophy developed, as demonstrated by angiocardiography, and the cardiac output decreased. After 14 to 22 months, the pulmonary stenosis was relieved surgically and the infundibular region was not resected. After 2 to 10 months there was still significant infundibular hypertrophy. The right ventricular pressure returned to normal levels and the cardiac output increased. These experiments suggest that infundibular hypertrophy is an acquired complication of main pulmonary artery stenosis in the dog. In the human, valvotomy in infancy may prevent the development of infundibular hypertrophy. Valvotomy alone may be all that is needed, when there is an immediate drop in the right ventricular pressure, below 100 mm. Hg, at time of operation.