Diagnostic advances and opportunities in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterised by the presence of thromboembolic material in the pulmonary circulation, and patients have a poor prognosis without treatment. Patients present with nonspecific symptoms, such as breathlessness and syncope, which means that other more common conditions are sometimes suspected before CTEPH, leading to delayed diagnosis and treatment. This is problematic because CTEPH is potentially curable with surgical pulmonary endarterectomy (PEA); indeed, CTEPH should always be considered in any patient with unexplained pulmonary hypertension (PH). Several key evaluations are necessary and complementary to confirm a diagnosis of CTEPH and assess operability. Echocardiography is initially used to confirm a general diagnosis of PH. Ventilation/ perfusion scanning is then essential in the first stage of CTEPH diagnosis, with a wedge-shaped perfusion deficit indicative of CTEPH. This should be followed by right heart catheterisation (RHC) which is mandatory in confirming the diagnosis and providing haemodynamic parameters that are key predictors of the risk associated with PEA and subsequent prognosis. RHC is ideally coupled with conventional pulmonary angiography, the gold-standard technique for confirming the location and extent of disease, and thus whether the obstruction is surgically accessible. Computed tomographic pulmonary angiography is also now routinely used as a complementary technique to aid diagnosis and operability assessment. Recent improvements in the resolution of other noninvasive techniques, such as cardiac magnetic resonance imaging, allow for detailed reconstructions of the vascular tree and imaging of vessel defects, and interest in their use is increasing.