Iloprost was the first inhaled prostacyclin analogue to be FDA-approved for the treatment of pulmonary arterial hypertension. Iloprost aerosol has been shown to significantly improve pulmonary hemodynamics in patients with idiopathic pulmonary hypertension (PH), with an effect greater than nitric oxide and sildenafil. It has also been shown to be more effective than nitric oxide at reducing pulmonary arterial pressure (PAP) than prostacyclin infusion when used in the cardiac catheterization laboratory. Because of its administration through inhalational means, iloprost has the advantage of selective action on the pulmonary vasculature with avoidance of the systemic side effects that plague many of the other treatments for PH. The investigators intend to compare the efficacy of inhaled iloprost in reducing pulmonary artery pressure to the gold standard of nitric oxide in patients with pulmonary hypertension.~Without an established noninvasive algorithm to identify beneficial hemodynamic response to vasodilators, patients with pulmonary hypertension (PH) are routinely subjected to expensive and invasive testing. Echocardiography is routinely used to facilitate a diagnosis of PH and a few echocardiographically-derived estimates have even been shown to correlate with vasodilator responsiveness and survival. Dynamic, real time changes in echocardiographic parameters have not been previously evaluated as a predictor of vasodilator responsiveness or of clinical outcome. The investigators will examine whether echocardiographic changes in response to inhaled iloprost can predict invasively derived vasodilator responsiveness and help assess prognosis in patients with pulmonary hypertension, possibly even obviating the need for invasive testing.
This study will compare the clinical efficacy of inhaled iloprost as an invasive, selective vasodilator in the cardiac catheterization laboratory in patients with pulmonary hypertension to the gold standard of inhaled nitric oxide. It will also examine whether echocardiographic estimates of response to inhaled iloprost can predict responsiveness to invasive vasodilator testing in patients with pulmonary hypertension.