Incidence and clinical course of chronic thromboembolic pulmonary hypertension with or without a history of venous thromboembolism in Denmark

A considerable number of patients with chronic thromboembolic pulmonary hypertension (CTEPH) lack a history of venous thromboembolism (VTE). We aimed to examine the annual incidence and prevalence of CTEPH in Denmark and to compare the rates of VTE, bleeding, and mortality between CTEPH patients with and without a history of VTE. The Danish National Patient Registry covering all Danish hospitals was used to identify all CTEPH cases between 2009 and 2018, based on combinations of discharge diagnoses using International Classification of Diseases, 10th Revision codes for CTEPH and relevant diagnostic and/or therapeutic interventions. Incidence rates of CTEPH per 100 000 person-years, rates of VTE and bleeding, and 5-year survival estimates were calculated. In total, 509 CTEPH patients were identified, of whom 82% had a history of VTE. The yearly incidence rate of CTEPH was 0.5 to 0.8 per 100 000 person-years during the study period. Patients with a history of VTE experienced a 2.5-fold rate of VTE compared with those without prior VTE (2571 vs 980 per 100 000 person-years), while the rate of bleeding events was lower (5008 vs 7139 per 100 000 person-years). The 5-year survival of CTEPH patients with a VTE history was 65% (95% CI, 58%-71%) compared with 45% (95% CI, 31%-58%) in patients without a history of VTE. The Danish incidence rate of CTEPH was comparable with that of other European countries. We identified notable differences in the prognosis of patients with CTEPH with or without a history of VTE. These findings may support generation of hypotheses regarding the pathophysiology of CTEPH and inform current patient care.