Fig. 2

Capillary density. Error bars represent the mean capillary density ± standard deviation (SD) in healthy controls (9.7 ± 0.81 loops/mm), patients with idiopathic pulmonary arterial hypertension (IPAH) (8.4 ± 1.2 loops/mm) and patients with chronic thromboembolic pulmonary hypertension (CTEPH) (8.0 ± 1.2 loops/mm). Difference in capillary density was significant among the three groups (p < 0.001). In detail, patients with IPAH presented significantly lower capillary density compared to healthy controls (*p < 0.01). In addition, patients with CTEPH presented significantly lower capillary density compared to healthy controls (**p < 0.001). No difference in capillary density was found between IPAH and CTEPH patients