The difference is likely tied to numerous factors, but older age and a poor transfer of gas (abnormal oxygen-carbon monoxide transfer) in the lungs among scleroderma patients was seen to contribute.
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.
Patients with scleroderma-associated PAH have less severe blood flow abnormalities in the lungs, yet studies show that they often have poorer survival than those with iPAH. In an attempt to trace the reasons for this difference, researchers at the Royal Hallamshire Hospital in the U.K. compared the features of a large group of newly diagnosed PAH patients.
The team first identified 651 patients with iPAH and scleroderma PAH (SSc-PAH). To exclude the risk of misdiagnosis, they then identified patients with risk factors for left heart disease or the presence of fibrotic lung disease, arriving at 375 patients with “pure” iPAH and Ssc-PAH.
Analyses showed that iPAH patients were younger and — as noted in earlier studies — had more severe blood flow impairment in the lungs. They also had much better exercise capacity.
Diffusion capacity for carbon monoxide (DLCO) — a measure of how efficiently gases are transported in the lung tissue — was lower among SSc-PAH patients, as it was among those excluded from the main analysis because of other lung and heart issues.
When investigating treatment patterns, the team noted that both groups used oral combination therapy to the same extent, but iPAH patients were more likely to be treated with inhaled, subcutaneous or intravenous prostanoids. Oral treatment with only one drug was linked to poorer survival compared to oral combination therapy.
When analyzing survival, the research team also looked at how long those with other heart and lung problems lived. Patients with iPAH survived for a median of 7.8 years, while those with iPAH and left heart disease lived for a median of 3.4 years, and iPAH with other lung disease for 2.1 years.
Scleroderma PAH patients lived for a median of three years, even with no further impact of left heart disease and only a slight, non-significant impact of additional lung disease.
“Survival in SSc-PAH is worse than in IPAH,” the team wrote.
Researchers concluded that a diagnosis of scleroderma, older age, lower gas diffusion capacity, lung artery oxygen saturation, and heartbeat volume predicted a shorter survival. Analyzing prognostic factors separately in the two diagnostic groups showed that in scleroderma patients, prognosis was linked to gas transfer and heartbeat volume, while iPAH survival was dependent on gas transfer and oxygen saturation.
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