NOTCH3 and idiopathic pulmonary arterial hypertension: Kaplan–Meier survival curves for all 341 individuals with IPAH in the combined cohort (San Diego, Phoenix and Boston) demonstrated that those with serum NOTCH3-ECD levels above the diagnostic cutoff of 13.0 ng ml−1 were 3.3× more likely to die within 3 years (hazard ratio (HR) 3.32, 95% CI, 1.8–6.0; P < 0.001) (Fig. 4a) and 3.7× more likely to die or undergo a transplantation within 3 years (HR 3.67, 95% CI, 2.1–6.5; P < 0.001) (Fig. 4b).