Age and Poorer Oxygen-Carbon Monoxide Exchange May Lessen Survival in PAH Patients with Systemic Sclerosis

Older age and abnormal oxygen-carbon monoxide blood levels may lead to poorer survival in patients with systemic sclerosis (SSc) and pulmonary arterial hypertension (PAH), compared to patients with idiopathic pulmonary arterial hypertension (IPAH), a new study reports.

The study, “Idiopathic And Systemic Sclerosis Associated Pulmonary Arterial Hypertension: A Comparison Of Demographic, Haemodynamic And Magnetic Resonance Imaging Characteristics And Outcomes,” was published in the journal Chest.

SSc is characterized by the development of fibrosis in the skin and other organs, and impaired blood flow.

The two most common forms of PAH are IPAH and SSc-associated PAH (SSc-PAH). Previous data have shown that pulmonary anomalies are less severe in SSc-PAH, but survival is higher in IPAH. But the reasons for this difference remain elusive.

The study enrolled 375 patients diagnosed either with IPAH or SSc-PAH to compare differences and outcomes. Medical assessment included Cardiac Magnetic Resonance (CMR) and right heart catheter (RHC) measurements.

Results showed that median survival time in IPAH patients was 7.8 years, and 3 years in the SSc-PAH group. SSc-PAH patients were also found to be older and to have less severe pulmonary changes, although they had poorer oxygen-carbon monoxide gas exchange (reduced gas transfer; DLCO or diffusing capacity for carbon monoxide) in their lungs.

Factors such as older age, the presence of SSc, a lower DLCO, and pulmonary artery saturation were independently associated with a poorer outcome.

There was no significant difference in left ventricular volumes between the groups, but the right ventricle’s volume and mass were significantly higher in IPAH patients than in SSc-PAH patients. The analysis also showed that the link between ventricular mass index (measured by CMR) and pulmonary vascular resistance was stronger in SSc-PAH than in the other group.

“Survival in SSc-PAH is worse than in IPAH. This difference is not just a reflection of the older age of patients with SSc-PAH,” the researchers wrote. “DLCO is lower in SSc-PAH and is an important prognostic factor in both forms of PAH. The reason for the lower DLCO in SSc-PAH merits further investigation.”

And, they concluded, “The reasons for poorer outcomes in SSc-PAH are likely to be multifactorial including, but not limited to, older age and reduced gas transfer.”