VCAM1 and pulmonary arterial hypertension: Both ICAM-1 and VCAM-1 transpulmonary gradients had moderate negative correlation with surrogates of PAH severity: ICAM-1 (AAO vs. PA) vs. mPAP/mSAP ratio (rho = −0.47, p = 0.044; Figure 3A) and VCAM-1 (AAO vs. PA) vs. dPAP/dSAP ratio (rho = −0.42, p = 0.079; Figure 3B).