Assessment of endpoints in pulmonary arterial hypertension associated with connective tissue disease

Connective tissue disease-associated pulmonary arterial hypertension (PAH) is mostly related to systemic sclerosis, overlap syndromes with features of systemic sclerosis, mixed connective tissue disease, and systemic lupus erythematosus. It is an important cause of mortality in these conditions and represents up to one third of patients seen in most specialist pulmonary hypertension centers. Patients with PAH associated with connective tissue disease may have a worse outcome than those with other forms of PAH. Most randomized clinical trials of PAH therapies have included patients with connective tissue disease as part of a mixed population. Overall, analyses suggest that treatment responses parallel those seen in idiopathic PAH, though subgroup analyses must be interpreted with caution. There may also be significant comorbidity from other pulmonary complications such as interstitial fibrosis, aspiration, or chest wall restriction. In addition, the majority of clinical trials have used 6-minute walk distance as the primary endpoint; the clinical relevance of this is questionable in connective tissue disease patients, who often have multiple comorbidities, other than PAH, which adversely affect exercise tolerance.