IL6 and pulmonary arterial hypertension: 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.