Systemic Sclerosis Patients At Higher Risk To Develop PAH
The study, published in the Seminars in Arthritis & Rheumatism, set out to understand the natural history of pulmonary hypertension (PH) in systemic sclerosis (Ssc), through a prospective longitudinal cohort study they called Pulmonary Hypertension Assessment and Recognition of Outcomes in Scleroderma (PHAROS).
They first defined “at risk” PAH by criteria that included an echocardiogram systolic pulmonary arterial pressure over 40 mmHg, diffusion lung capacity of carbon monoxide below 55%, or a ratio of percentage of forced vital capacity/percentage diffusion lung capacity of carbon monoxide higher than 1.6, as measured by pulmonary function testing. The team followed up patients annually and right heart catheterization was performed if pulmonary hypertension was suspected.
Over a mean follow-up of 2.5 years, a total of 251 “at-risk” subjects with a mean age at the date of entry of 56.7 years were enrolled between 2005 and 2012. Of the 251 patients, 82 had right heart catheterization , and 35 were confirmed to have new pulmonary hypertension.
Results showed that 76% of these 35 patients met the pulmonary function testing criteria, and had a mean diffusion lung capacity of carbon monoxide of 46.4% (lower than the 55% predicted to define “at risk” PAH), compared with 51.3% for the remaining at-risk patients who didn’t develop PAH. This resulted in an average ratio of function testing criteria to diffusion lung capacity of carbon monoxide of 2.0% versus 1.8%.
In addition, patients who developed PAH were significantly more likely to have exercise-induced hypoxia, at a rate of 53.9% versus 23.5% of those who did not develop PAH. They also had a shorter average 6-minute walk test, at 353 versus 422 metres.
Researchers found that a low diffusion lung capacity of carbon monoxide, a high forced vital capacity/ diffusion lung capacity of carbon monoxide ratio, exercise-induced hyposia and an entry echo systolic pulmonary arterial pressure higher than 40 were strongle associated with future pulmonary hypertension. Right heart catheterization was, however, necessary to confirm or exclude PAH, the team added, concluding that these high-risk factors do predict future pulmonary hypertension.