Pulmonary Endarterectomy Surgery—A Technically Demanding Cure for WHO Group IV Pulmonary Hypertension: Requirements for Centres of Excellence and Availability in Canada

There are 5 categories in the World Health Organization (WHO) classification of pulmonary hypertension (PH): (1) pulmonary arterial hypertension; (2) PH associated with left heart disease; (3) PH associated with hypoxia or lung disease; (4) chronic thromboembolic PH (CTEPH); and (5) PH of miscellaneous aetiology (eg, sarcoidosis, extrinsic compression). Group 1 PH is the only category for which there is approved, PH-specific medical therapy. These medications (phosphodiesterase 5 inhibitors, prostanoids, and endothelin antagonists) improve functional class and exercise tolerance but are not curative. The only form of adult PH that is curable (other than by lung or heart-lung transplantation) is Group 4 PH (CTEPH), which can be reversed by surgical pulmonary endarterectomy (PEA). The diagnosis of CTEPH is often delayed because the onset of symptoms is insidious and the symptoms themselves are nonspecific. CTEPH patients usually present with dyspnea, and fatigue, often of many years duration. Thus a high degree of suspicion is required to detect CTEPH. Symptoms are related to impaired cardiac output and right ventricular failure and result from obstruction of the pulmonary arteries by unresolved thrombus, compounded, in some cases, by a poorly understood vasculopathy. The US Healthcare Cost and Utilization Project (HCUP) database suggests a 3.4% incidence of CTEPH in patients with a pulmonary embolism (reviewed in Jaff et al.). CTEPH is often discovered on cardiothoracic (CT) angiography or ventilation/ perfusion scans conducted in the course of a systematic investigation of unexplained PH. Fully 2 of 3 CTEPH patients have no clinical history of pulmonary embolism. The 1-year untreated mortality rate in CTEPH ranges from 12%-24% and is predicted by the pulmonary artery (PA) pressure