Clinical assessment of pulmonary hypertension

Abstract

Pulmonary arterial hypertension (PAH) is primarily a disease of pulmonary vascular resistance (PVR) caused by proliferation and contraction of vascular smooth muscle cells. PAH is a frequent complication of systemic sclerosis (SSc) observed with a prevalence of 8-12% [1-3] due to a proliferative arterial pulmonary microangiopathy. A recent meta-analysis of more than 3,500 SSc patients demonstrated a prevalence of PAH, based on right heart catheterization (RHC) of slightly less than 10% [4]. In order to diagnose PAH, it is necessary to establish the appropriate cardiopulmonary hemodynamics, mPAP ≥ 25 mmHg, PCWP or left ventricular end diastolic pressure ≤ 15 mmHg, and a PVR ≥ 240 dyn/cm -5 (3 Wood units); currently, the only available method for detecting and assessing these and other important cardiopulmonary hemodynamic parameters (i.e., cardiac output) is RHC; thus, RHC should be performed in all cases in which PAH is suspected. It not only confirms the presence of pulmonary hypertension (PH) and enables the establishment of a specific diagnosis of PAH, but it also eliminates other cardiac etiologies and assesses the degree of right heart dysfunction [5]. Within the last two decades, pulmonary fibrosis and PAH have become the leading causes of morbidity and mortality in SSc patients [6]. The estimated 3-year survival among patients with PAH associated with SSc is approximately 50% [7]. The development of PAH in SSc must be differentiated from pulmonary fibrosis associated PH. Distinguishing PAH from PH associated with pulmonary fibrosis is not always easy, especially since some patients can have both pulmonary fibrosis and a true pulmonary vasculopathy (PAH). However, if lung volumes (forced vital capacity, FVC and/or total lung capacity, TLC) are <60% of the predicted value and mPAP <35 mmHg at rest, PH is deemed more likely related to pulmonary fibrosis [8]. When lung volumes (CPT and/or CVF) are >70% of the predicted value, the PH is considered more likely to be PAH. When lung volumes (CPT and/or CVF) are between 60% and 70% of the predicted value, the diagnosis becomes more difficult; however, if mPAP is >35 mmHg, the PH is considered out of proportion (or reactive) and most probably reflects a true pulmonary artery microangiopathy. Nevertheless, as noted, PH due to hypoxemia and PAH may coexist in SSc patients. In this review, we will mainly focus on PAH.