Mean follow-up time was 942 days (range, 242-2,359 days). During follow-up, the PAD increased significantly (Table 3). In 37 (73%) patients with PAH, the diameter increased (mean, 3 ± 3 mm; range, 0.2-17 mm). In 11 (22%) patients, the diameter decreased (mean, -2 ± 2 mm; range, -0.2-5.4 mm). In three patients, the diameter remained unchanged. PVR decreased, and CO increased, both significantly, under treatment during follow-up (Table 3). Figure 4 shows a plot of the change of PAD against the change in mPAP. Of the 11 patients with a decreased diameter, only three had a decrease > 2 mm. The mPAP in these three patients was normalized or almost normalized under treatment; the mPAP at follow-up ranged from 15 to 28 mm Hg. In patients with an increased PAD at follow-up, the pressure either increased or decreased, and no relation was found between PAD change and pressure change. Figure 5 shows that there were no significant differences between tertiles regarding CO, mPAP at baseline, and PAD at baseline. In contrast, diameter change across tertiles of follow-up time differed significantly for the outermost tertiles, whereas the changes in CO and mPAP were not different over the tertiles. Overall, a moderate correlation between follow-up time and diameter change was found (r = 0.56; P < .001). Neither a relation between changes in PAD and pulse pressure at baseline (r = -0.21; P = .14) nor a relation between changes in PAD and pulse pressure changes during follow-up (r = 0.16; P = .27) was found.