Serum IL-1β was not altered, but this is unsurprising given the inherent difficulties in measuring this cytokine.47 In high-risk patients with PAH and concomitant atherosclerosis, worsening endothelial function and raised inflammatory markers such as CRP and IL-6 are quantifiable; thus, our data suggest macitentan may be of most benefit to these patients. This evidence concerns the gene IL1B and pulmonary arterial hypertension.