Previous studies have identified survival in systemic sclerosis (SSc)-associated pulmonary arterial hypertension (SSc-PAH) to be worse than in idiopathic pulmonary arterial hypertension (IPAH). We investigated differences between these conditions by comparing demographic, haemodynamic and radiological characteristics and outcomes in a large cohort of incident patients.
651 patients diagnosed with IPAH or SSc-associated pre-capillary pulmonary hypertension were included. Patients with lung disease or ≥2 risk factors for left heart disease were identified leaving a primary analysis set of 375. Sub-group analysis of cardiac magnetic resonance imaging was performed.
Median survival was 7.8 years in IPAH and 3 years in SSc-PAH (p<0.001). SSc-PAH patients were older with less severe haemodynamics but lower gas transfer (DLCO). Independent prognostic factors were age, SSc, DLCO, pulmonary artery saturation and stroke volume. After excluding patients with normal or only mildly elevated resistance there was no difference in the relationship between pulmonary vascular resistance and compliance in IPAH and SSc-PAH. The relationship between mean pulmonary arterial pressure (mPAP) and systolic pulmonary arterial pressure (sPAP) in IPAH was identical to that previously reported (mPAP = 0.61sPAP + 2mmHg). The relationship in SSc-PAH was similar: mPAP = 0.58sPAP + 2mmHg (p-value for difference with IPAH=0.095). The correlation between ventricular mass index assessed at cardiac magnetic resonance imaging and pulmonary vascular resistance was stronger in SSc-PAH.
The reasons for poorer outcomes in SSc-PAH are likely to be multifactorial including, but not limited to, older age and reduced gas transfer.