Pathophysiology of Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Abstract

The prevalence and incidence of chronic thromboembolic pulmonary hypertension (CTEPH) following acute pulmonary embolism (PE) is difficult to ascertain. However, recent follow-up studies in patients presenting with acute PE give an indication of the scale of the problem. An early study followed an unselected series of PE patients and found evidence of CTEPH in four patients (5.1%).¹ Pengo et al. subsequently showed a cumulative incidence of 3.8% at 2 years, while even more recent studies by Becattini et al. and Miniati et al. have described cumulative incidences of 4/320 (1.3%) and 2/259 (0.8%), respectively.^2–4 Given that acute PE is as common as 1 per 1,000 of the population per year,⁵ suggesting the annual incidence of CTEPH following acute venous thromboembolism is of the order of 8 to 51 cases per 1 million population. Moreover, given that CTEPH may be classically described as presenting some time following an acute event,⁶ the results from these relatively short studies may represent an underestimate. A further consideration is that up to 60% of patients with CTEPH do not have a previously documented VTE event.⁷ In these patients, it is presumed that clinically “silent” emboli in the past have triggered the disease process.