Pulmonary hypertension in patients with moderate to severe hypersensitivity pneumonitis

Background Hypersensitivity pneumonitis (HP) is characterized by a complex immunological reaction of the lung that may lead to chronic interstitial lung disease (ILD). Pulmonary hypertension (PH) may aggravate the clinical picture. We aimed to assess the prevalence of PH in two independent cohorts including patients with moderate and severe HP. Patients and Methods We retrospectively analyzed the data of HP patients with severe ILD undergoing lung transplantation (cohort-1) and invited HP patients with mild disease participating at pulmonary rehabilitation for a prospective screening for PH (cohort-2). The presence of PH was assessed by both echocardiography and right heart catheterization (RHC). Results In cohort 1 (n = 55, median age 57 [95% CI 52-60] years, 59% male, forced vital capacity [FVC] 37 [35-45] % predicted), echocardiographic systolic pulmonary arterial pressure (sPAP) was available in 31 patients and showed elevated values (53 [45-63] mmHg). Sixteen patients (29%) had a high probability of pulmonary hypertension (PH; sPAP > 50 mmHg). Based on clinical assessment, a non-invasive evaluation using echocardiography was performed in accordance with current guideline recommendations, followed by invasive assessment with right heart catheterization (RHC) in selected patients. RHC was performed in 21 patients, revealing a mean pulmonary arterial pressure (mPAP) of 28 (24-33) mmHg and a pulmonary vascular resistance (PVR) of 2.8 (2.2-3.4) Wood units; PH was confirmed in 15 patients (71% of those undergoing RHC, 27% of the total cohort). In cohort 2 (n = 96, median age 62 [60-65] years, 66% male, FVC 98 [95-104] % predicted), echocardiographic screening was available in 88 patients and showed upper-normal sPAP values (29 [28-31] mmHg). One patient (1%) had a high probability of PH. Following clinical assessment and guideline-recommended non-invasive screening, RHC was performed in 13 patients with suspected PH. Hemodynamic measurements showed an mPAP of 19 (16-21) mmHg and a PVR of 1.9 (1.7-2.8) Wood units; PH was confirmed in 5 patients (38% of those undergoing RHC, 5% of the total cohort). All five patients had a plausible alternative explanation for their PH. Conclusion PH is a frequent complication in patients with HP and severe ILD. In HP patients with mild disease, PH is uncommon and alternative causes should be considered.