Chronic thromboembolic and pulmonary arterial hypertension share acute vasoreactivity properties

Background: Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are the major classes of pulmonary hypertensive disorders according to the World Health Organization; both lead to right heart failure and death. A better understanding of disease mechanisms has led to the suggestion that the thromboembolic and nonthrombo-embolic types of pulmonary hypertension may share pathophysiologic features. We therefore compared acute vasoreactivity and proximal pulmonary artery compliance in patients with PAH and CTEPH during the initial diagnostic heart catheterization. Methods: Right heart catheterization using a flow-directed Swan-Ganz catheter was performed in patients with CTEPH (n = 22) and PAH (n = 35). Pulmonary hemodynamics were assessed at baseline, during the inhalation of 40 ppm of nitric oxide, and 30 min after the inhalation of 10 mu g of iloprost. To assess the proximal pulmonary artery compliance, the pulse pressure (PP) [systolic - diastolic pressure] and the fractional PIP (PPf) [divided by the mean pressure] were calculated. Results: Both vasodilators produced similar hemodynamic improvement, and the difference between CTEPH and PAH was not significant. The baseline PP and PPf did not vary between the two groups. Conclusion: Patients with PAH and CTEPH show similar acute vasoreactivity to inhaled nitric oxide and iloprost, and have similar pulmonary artery compliance. These findings support the presence of some shared pathophysiologic pathways in both disorders and may lead to therapeutic implications in patients with inoperable CTEPH.