Pulmonary hypertension in lymphangioleiomyomatosis: prevalence, severity and the role of carbon monoxide diffusion capacity as a screening method

Abstract

Background: Lymphangioleiomyomatosis (LAM) is included within group 5 of the current PH classification (unclear multifactorial mechanisms). However, data regarding the occurrence of PH in LAM are scarce. The aims of the study were to describe the prevalence and characteristics of PH in a large cohort of LAM patients with different levels of severity, and to evaluate the role of echocardiography and carbon monoxide diffusion capacity (DL_CO) as screening methods for PH in LAM.

Methods: One hundred five LAM patients underwent transthoracic echocardiography, pulmonary function tests (PFTs) and 6-min walk test (6MWT). Patients with a suspicion of PH on echocardiography, defined by the presence of estimated systolic pulmonary artery pressure (PAP) over 35 mmHg or PFT showing DLco below 40% of the predicted value, underwent right heart catheterisation to confirm the diagnosis of PH.

Results: Eight patients (7.6%) had PH confirmed on right heart catheterisation, six patients (5.7%) had a pre-capillary pattern and two patients (1.9%) had a post-capillary profile. Only one patient (1%) had mean PAP over 35 mmHg. Patients with PH had lower FEV₁ and DL_CO in PFTs and greater oxygen desaturation and dyspnea intensity during 6MWT compared with those without PH. In 63% of the patients with confirmed PH, the right heart catheterisation was performed based only on DL_CO result.

Conclusions: The prevalence of PH is low in LAM patients. Pulmonary hypertension in LAM is typically mild and significantly associated with pulmonary parenchymal involvement. Carbon monoxide diffusion capacity significantly improved the identification of PH in LAM patients.

Keywords: Echocardiography; Lymphangioleiomyomatosis; Prevalence; Pulmonary hypertension; Right heart catheterisation.

Fig. 1

Patient disposition. Definition of abbreviations: 6MWT: six-minute walk test; DL_CO: lung diffusing capacity for carbon monoxide; mPAP: mean pulmonary arterial pressure; PAP: pulmonary arterial pressure; PFT: pulmonary function tests; PH: pulmonary hypertension; RHC: right heart catheterisation

Fig. 2

Comparison of FEV₁ and DL_CO between PH vs. non-PH groups. Definition of abbreviations: DL_CO: lung diffusing capacity for carbon monoxide; FEV₁: forced expiratory volume in the first second; PH: pulmonary hypertension. *p < 0.001. Box plots show the quartiles (box limits), the 10th and 90th percentiles (error bars) and the median (line)