Management of primary pulmonary hypertension.

When Paul Wood first described primary pulmonary hypertensionl 2 he believed it to have a vasoconstrictive origin and showed that the pulmonary vascular resistance could be selectively lowered in some but not all of these patients by infusion of acetyl choline into the pulmonary artery3 in contrast to patients with the Eisenmenger syndrome, who were invariably unresponsive.34 The pathogenesis has since been argued, microthromboembolism and thrombosis in situ having some proponents, but the concept of an increased smooth muscle tone perhaps generated by endothelial damage and platelet activity has gained ground. Efforts to find an effective orally active specific pulmonary arteriolar dilator have continued over the years but with little success, though there has been considerable recent resurgence of interest. Observations made in beef cattle grazing at high altitude and in humans living and exercising at altitude have shown an individual and species variability suggesting a genetically determined hyperreactivity.5 This pulmonary hypertension is reversible on return to sea level, and the incidence of primary pulmonary hypertension is seemingly higher in populations living at high altitudes.6 Childhood7 and familial cases are weli known,8 and an association with Raynaud's phenomenon was early noted.9 In the European epidemic of primary pulmonary hypertension, which was linked with the slimming drug aminorex fumarate, only an estimated 0-2% of individuals taking the drug developed the disease and the condition was usually reversible.'0 Primary pulmonary hypertension has also been linked with fenfluramine,II an anorectic which is still available. A concept of idiosyncratic pulmonary hypertension of possible dietary origin grew from this experience and from observations of a malignant type of pulmonary hypertension in rats who had eaten seeds ofCrotalaria spectabilis which contains the alkaloid monocrotaline.'2