Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension

> “The historian of science may be tempted to claim that when paradigms change, the world itself changes with them. Led by a new paradigm, scientists adopt new instruments and look in new places … see new and different things when looking with familiar instruments in places they have looked before.”1 Chronic thromboembolic pulmonary hypertension (CTEPH), increasingly recognized as occurring in some 2% to 4% of people experiencing pulmonary embolism, rivals idiopathic pulmonary arterial hypertension (PAH) in its poor untreated outcome, with rapid progression to increasing fatigue, breathlessness, right-ventricular dysfunction and failure, and untimely death.2 Intraluminal thrombus organization is accompanied by fibrous and inflammatory narrowing of directly affected vessels and is accompanied by inflammatory remodeling effects in overcirculated and pressurized pulmonary arterial segments that were not mechanically obstructed. Effects on pulmonary blood flow distribution, ventilation and gas exchange, and right-ventricular afterload and function are profound.3 To date, therapy for CTEPH has largely focused on surgically based pulmonary thromboendarterectomy (PEA) followed by adjunctive chronic anticoagulation.4 (Targeted medical therapies designed for PAH seem to have real, but limited, benefit for individuals with CTEPH.5) When PEA is performed in centers with combined medical, surgical, and perioperative experience and expertise, results may be highly favorable, particularly in individuals with fewer medical comorbidities, with more proximally located obstruction, with greater preoperative efficiency of ventilation or vascular responsiveness to pulmonary vasodilator testing, and with lower preoperative pulmonary vascular resistance.2 However, heterogeneity of pathological and clinical presentation, combined with lack of uniform access to high-volume expert surgical centers, continues to contribute to 10% to 50% of patients with CTEPH …