Page 97 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

Introduction
Patients with pulmonary hypertension tend to have a mildly reduced pulmonary diffusion capacity for carbon monoxide (DLCO) compared to healthy subjects [1]. A severely reduced DLCO is most often seen in pulmonary hypertension related to connective tissue disease, lung parenchymal disease or in pulmonary veno-occlusive disease, but also in a subset of patients with idiopathic pulmonary arterial hypertension (IPAH) without signs of these underlying conditions [2-5]. Recent studies revealed that IPAH patients with a low DLCO have a worse survival [6]. Although it is yet unknown what causes this difference in survival, it has been argued that compared to other IPAH patients, IPAH patients with a severely reduced DLCO may have a distinct type of pulmonary vasculopathy that is less responsive to PAH-specific therapy [7,8]. Therefore, the aim of this study was to compare the response to pulmonary arterial hypertension specific vasodilatory therapy in terms of hemodynamics, cardiac function, exercise capacity and oxygenation between IPAH patients with different degrees of DLCO impairment.
Methods
We studied retrospectively treatment naïve hereditary- and IPAH patients who were diagnosed between January 1990 and May 2015 at the VU University Medical Center. Part of this cohort was described in the study of Trip et al. [5]. A diagnosis of hereditary- and IPAH was established by a multidisciplinary PH team, after rigorous clinical evaluation according to the ERS/ESC guideline [9]. Subjects without available baseline DLCO measurement, with severe emphysema or pulmonary fibrosis on HRCT [5] were excluded from this study. Furthermore, to avoid clouding of the results, patients carrying a BMPR2 mutation were excluded from this study as recent studies showed the reduced life-expectancy but preserved DLCO status in these subjects [4, 10]. In total 166 patients were included in this study (figure 1). The cohort was divided into three groups using tertiles, leading to one group with a severely reduced DLCO (<43%), one group with a moderately reduced DLCO (43%-62%) and one group with a preserved DLCO (>62%).
Right heart catheterization
Hemodynamics and RV pressure curve recordings were assessed with a balloon-tipped, flow directed 7.5F triple lumen Swan-Ganz catheter (Edwards Lifesciences LLC, Irvine, CA, USA). Cardiac output measurements were performed using thermodilution or the direct Fick method.
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