Pulmonary Hypertension in Patients with Moderate to Severe Hypersensitivity Pneumonitis

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 2 independent cohorts including patients with moderate and severe HP.

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).

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] mm Hg). Sixteen patients had a high probability of PH (sPAP >50 mm Hg). RHC was performed based on clinical suspicion of PH or as part of the clinical assessment for transplantation in 21 patients, revealing a mean pulmonary arterial pressure (mPAP) of 28 (24-33) mm Hg and a pulmonary vascular resistance (PVR) of 2.8 (2.2-3.4) Wood units in this group; 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] mm Hg). One (1%) patient had a high probability of PH. Following noninvasive clinical assessment, RHC was performed in 13 patients with suspected PH. Hemodynamic measurements showed an mPAP of 19 (16-21) mm Hg and a PVR of 1.9 (1.7-2.8) Wood units in this group, and PH was confirmed in 5 patients (38% of those undergoing RHC, 5% of the total cohort). All 5 patients had a plausible alternative explanation for their PH.

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.