Group 4: Chronic thromboembolic pulmonary hypertension
Chronic thromboembolic pulmonary hypertension (CTEPH) was included in Group 4. The incidence of CTEPH is uncertain. CTEPH represents however a frequent cause of PH and occurs in up to 4% of patients after an acute pulmonary embolism [71,72]. In the classification from the third World Symposium on PH, CTEPH was divided into 2 subgroups: proximal CTEPH and distal CTEPH, depending on the feasibility of performing pulmonary thromboendarterectomy. Currently, there is no consensus about the definitions of proximal and distal CTEPH and the decision of surgery may vary depending on individual centers [73]. Thus, the Dana Point Classification propose only one group irrespectively of proximal or distal obstruction. Patients with suspected or confirmed CTEPH need to be referred to expert centers with experience in the management of CTEPH, to consider the feasibility of performing surgery. The indication for surgery depends on the location of the obstruction, the correlation between hemodynamics and the degree of obstruction assessed by angiography, comorbidities, the willingness of the patient, and the experience of the surgeon [74,75]. Patients who are not candidates for surgery may benefit from PAH-specific medical therapy [76,77]; however, further evaluation of these therapies in randomized control trials are needed [78].