Reversibility of lesions in experimental pulmonary hypertension. Preliminary observations.

Severe pulmonary hypertension with obliterative vascular disease was induced in 13 of 44 dogs subjected to systemic-to-pulmonary artery anastomosis to the left diaphragmatic lobe. In 11 of these, plus 4 with high pressure but normal histology and 4 with normotensive lobes, for a total of 19, reanastomosis to the main pulmonary artery was performed. Only 1 of the histologically abnormal lobes maintained vascular patency; the 5 other dogs with patent reanastomoses had normal vascular histology. Our findings support the reluctance of surgeons to correct cardiac shunts when obstructive vascular disease due to severe pulmonary hypertension is present; in humans pulmonary artery pressure would not drop as much as in our model since the pulmonary vascular resistance of both lungs is high. On the other hand, if a normal lung were transplanted at the same time, the retained abnormal lung would probably lose vascular perfusion.