C hronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism with uncertain prevalence, ranging from 0.4% to 9.1%. 1 Diagnosis is strongly associated with a history of acute venous thromboembolism (VTE). 2,3 It is caused by nonresolving fibrothrombotic obstructions of large pulmonary arteries, combined Background-Chronic thromboembolic pulmonary hypertension, a rare complication of acute pulmonary embolism, is characterized by fibrothrombotic obstructions of large pulmonary arteries combined with small-vessel arteriopathy. It can be cured by pulmonary endarterectomy, and can be clinically improved by medical therapy in inoperable patients. A European registry was set up in 27 centers to evaluate long-term outcome and outcome correlates in 2 distinct populations of operated and not-operated patients who have chronic thromboembolic pulmonary hypertension. Methods and Results-A total of 679 patients newly diagnosed with chronic thromboembolic pulmonary hypertension were prospectively included over a 24-month period. Estimated survival at 1, 2, and 3 years was 93% (95% confidence interval [CI], 90-95), 91% (95% CI, 87-93), and 89% (95% CI, 86-92) in operated patients (n=404), and only 88% (95% CI, 83-91), 79% (95% CI, 74-83), and 70% (95% CI, 64-76) in not-operated patients (n=275). In both operated and not-operated patients, pulmonary arterial hypertension-targeted therapy did not affect survival estimates significantly. Mortality was associated with New York Heart Association functional class IV (hazard ratio [HR], 4.16; 95% CI, 1. P=0.0065 and HR, 4.76; 95% CI, P=0.0021), increased right atrial pressure (HR, 1.34; 95% CI, 0.95-1.90; P=0.0992 and HR, 1.50; 95% CI, 1.20-1.88; P=0.0004), and a history of cancer (HR, 3.02; 95% CI, 1.36-6.69; P=0.0065 and HR, 2.15; 95% CI, 1.18-3.94; P=0.0129) in operated and not-operated patients, respectively. Additional correlates of mortality were bridging therapy with pulmonary arterial hypertension-targeted drugs, postoperative pulmonary hypertension, surgical complications, and additional cardiac procedures in operated patients, and comorbidities such as coronary disease, left heart failure, and chronic obstructive pulmonary disease in not-operated patients. Conclusions-The long-term prognosis of operated patients currently is excellent and better than the outcome of notoperated patients. with small-vessel arteriopathy in some patients. Both proximal and small-vessel obstruction increase pulmonary vascular resistance (PVR), leading to progressive pulmonary hypertension, right heart failure, and ultimately death. CTEPH can be cured by pulmonary endarterectomy (PEA) 4 and clinically improved by medical therapy. 5,6 Therefore, current guidelines recommend PEA as first-choice therapy, whereas the use of pulmonary arterial hypertension (PAH)-targeted drugs is restricted to inoperable patients or patients with persistent/recurrent pulmonary hypertension after PEA.7 Balloon pulmonary angioplasty, a new and promising treatment method for ...