Morphological substrate for the reversibility and irreversibility of pulmonary hypertension.

The reversibility of pulmonary hypertension in hypertensive pulmonary vascular disease depends, in the first place, on the feasibility of eliminating the cause of the elevation of pressure. Equally important in this respect are the type, the severity, and the extent of the pulmonary vascular lesions. This implies that various forms of pulmonary hypertension have completely different tendencies for regression. In thrombotic arteriopathy, whether caused by primary thrombosis or by embolism, the chance of regression of pulmonary hypertension, and of the vascular lesions, is limited. On the other hand, in many patients pulmonary venous hypertension and the associated vasculopathy, even when severe, appear potentially reversible. Experimental evidence suggests that the same is true in cases of hypoxic pulmonary hypertension as long as prominent complicating vascular alterations, as often observed in chronic obstructive lung disease, are absent. In plexogenic arteriopathy regression of pulmonary hypertension, following elimination of its cause, is observed whenever the vascular lesions have not progressed beyond a certain stage that can be considered a point of no return. Thereafter, there is not only no regression but a distinct tendency to progression of pulmonary vascular disease.