Vasodilator therapy for primary pulmonary hypertension.

Abstract

Primary pulmonary hypertension is a clinical syndrome characterized by pulmonary hypertension in the absence of sufficient underlying heart or lung disease to account for it (1-3). In essence, it is unexplained pulmonary arterial hypertension. Pulmonary venoocclusive disease, the etiology of which is also enigmatic, is generally considered separately because of the prospect of unique pathogenetic mechanisms and the distinctive pulmonary vascular lesions. Pulmonary vasodilator therapy is based on the premise that pulmonary vasoconstriction is an important component of the syndrome of pulmonary hypertension (1, 4). Even when the underlying disorder is predominantly one of obliterative intimal disease, it is believed that stretching of vessels due to increased intraluminal pressures leads to a secondary increase in the muscle tone of the pulmonary arteries and arterioles (5), an effect that may heighten pulmonary vascular resistance and worsen pulmonary hypertension. Unfortunately, the therapeutic use of pulmonary vasodilator agents has been hampered by difficulty in the early detection of pulmonary hypertension, by heterogeneity of the vascular lesions responsible for the clinical entity of primary pulmonary hyperten­ sion, and by uncertain criteria for a therapeutically meaningful response to pulmonary vasodilator agents. In this review, we briefly discuss the clinical diagnosis of pulmonary hypertension (PPH) and the testing of vasodilators for thera­ peutic effectiveness. In addition, we identify questions to be answered about the proper use of vasodilator agents in therapy.