Pulmonary hypertension in interstitial lung disease: Clinical trial design and endpoints: A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative-Group 3 Pulmonary Hypertension

Cluster analysis identifies novel real-world lung disease-pulmonary hypertension subphenotypes: implications for treatment response

Background

Clinical trials repurposing pulmonary arterial hypertension (PAH) therapies to patients with lung disease- or hypoxia-pulmonary hypertension (PH) (classified as World Health Organization Group 3 PH) have failed to show a consistent benefit. However, Group 3 PH clinical heterogeneity suggests robust phenotyping may inform detection of treatment-responsive subgroups. We hypothesised that cluster analysis would identify subphenotypes with differential responses to oral PAH therapy.

Methods

Two k-means analyses were performed on a national cohort of US veterans with Group 3 PH; an inclusive model (I) of all treated patients (n=196) and a haemodynamic model (H) limited to patients with right heart catheterisations (n=112). The primary outcome was organ failure or all-cause mortality by cluster. An exploratory analysis evaluated within-cluster treatment effects.

Results

Three distinct clusters of Group 3 PH patients were identified. In the inclusive model (C1I n=43, 21.9%; C2I n=102, 52.0%; C3I n=51, 26.0%), lung disease and spirometry drove cluster assignment. By contrast, in the haemodynamic model (C1H n=44, 39.3%; C2H n=43, 38.4%; C3H n=25, 22.3%), right heart catheterisation data surpassed the importance of lung disease and spirometry. In the haemodynamic model, compared to C3H, C1H experienced the greatest hazard for respiratory failure or death (HR 6.1, 95% CI 3.2-11.8). In an exploratory analysis, cluster determined treatment response (p=0.006). Conclusions regarding within-cluster treatment responses were limited by significant differences between select variables in the treated and untreated groups.

Conclusions

Cluster analysis identifies novel real-world subphenotypes of Group 3 PH patients with distinct clinical trajectories. Future studies may consider this methodological approach to identify subgroups of heterogeneous patients that may be responsive to existing pulmonary vasodilatory therapies.

[Pulmonary hypertension associated with lung disease]

Pulmonary hypertension (PH) is a multifactorial pulmonary vascular disease. PH associated with pre-existing lung disease is common and classified as group 3 in the clinical classification. Patients with chronic obstructive or interstitial lung disease are most likely to develop PH, with up to 20% of patients showing signs of PH. Distinguishing between the symptoms of the underlying lung disease and concomitant PH can be difficult. Clinical assessment, lung function tests, laboratory tests, and echocardiography can be helpful. The hemodynamic definition of PH has recently been changed. PH associated with lung disease is a pre-capillary form by definition. A special sub-stratification in group 3 is the differentiation of hemodynamic severity. Severe PH in group 3 is defined as a pulmonary vascular resistance (PVR) greater than 5 Wood units (WU). This pulmonary vascular phenotype is characterized by rather mild to moderate impairment of lung function or lung parenchymal destruction but with severe pulmonary vascular disease or right heart strain. Currently, there are no specific PH medications approved for group 3. However, the use of specific PH medications for the pulmonary vascular phenotype is being discussed in studies or on a case-by-case basis, while in patients with a PVR below 5 WU treatment focuses on the underlying disease.