**Pulmonary embolism**

Pulmonary embolism is an example of a pre-capillary PH. It may occur before, during or after CPB leading to the development or the exacerbation of PH. Thrombus, air and even carbon dioxide (Martineau et al., 2003) can cause pulmonary embolism. Pulmonary embolisms are rare in the immediate cardiac postoperative period. However, patients at risk include patients with predisposing factors to PH and patients with chronic thromboembolic pulmonary hypertension (CTEPH) (Fig. **6**). The incidence of CTEPH is uncertain, but it represents a frequent cause of PH occurring in up to 4% of patients after an acute pulmonary embolism (Pengo et al., 2004; Tapson & Humbert, 2006).

Fig. 6. Chronic pulmonary embolism. (**A, B**) Mid-esophageal ascending aorta (Ao) long-axis view in a 65-year-old woman with chronic pulmonary embolism shows the mobile clot adherent to the right pulmonary artery (RPA) wall. *(*LA: left atrium; LV: left ventricle). With permission from Denault *et al*. (Denault et al., 2010a).
