Diagnosis of chronic thromboembolic pulmonary hypertension

Abstract

Chronic thromboembolic pulmonary hypertension (CTEPH) is the only potentially curable form of pulmonary hypertension. Rapid and accurate diagnosis is pivotal for successful treatment. Clinical signs and symptoms can be nonspecific and risk factors such as history of venous thromboembolism may not always be present. Echocardiography is the recommended first diagnostic step. Cardiopulmonary exercise testing is a complementary tool that can help to identify patients with milder abnormalities and chronic thromboembolic disease, triggering the need for further investigation. Ventilation/perfusion (V'/Q') scintigraphy is the imaging methodology of choice to exclude CTEPH. Single photon emission computed tomography V'/Q' is gaining popularity over planar imaging. Assessment of pulmonary haemodynamics by right heart catheterisation is mandatory, although there is increasing interest in noninvasive haemodynamic evaluation. Despite the status of digital subtraction angiography as the gold standard, techniques such as computed tomography (CT) and magnetic resonance imaging are increasingly used for characterising the pulmonary vasculature and assessment of operability. Promising new tools include dual-energy CT, combination of rotational angiography and cone beam CT, and positron emission tomography. These innovative procedures not only minimise misdiagnosis, but also provide additional vascular information relevant to treatment planning. Further research is needed to determine how these modalities will fit into the diagnostic algorithm for CTEPH.

FIGURE 1

Cardiopulmonary exercise testing of a patient with chronic thromboembolic pulmonary hypertension showing fields 4, 6 and 9 of the Wasserman panel. a) Elevated slope of minute ventilation (V′_E)/carbon dioxide output (V′_CO2) ratio showing hyperventilation (field 4); b) elevated ventilator equivalents for oxygen (EQ_O2) and carbon dioxide (EQ_CO2) showing ineffective ventilation (field 6); c) low and decreasing end-tidal carbon dioxide tension (P_ETCO2), elevated alveolar–arterial oxygen tension gradient (P_A–aO2) and elevated arterial–end-tidal carbon dioxide gradient (P_a–ETCO2) (field 9). P_ETO2: end-tidal oxygen tension; P_aO2: arterial oxygen tension; P_aCO2: arterial carbon dioxide tension; P_O2: oxygen tension; P_CO2: carbon dioxide tension.

FIGURE 2

A 53-year-old patient with fibrosing mediastinitis. a) Anterior and b) posterior views from a perfusion scintigraphy scan show multiple segmental perfusion defects (arrows). c) Volume-rendered computed tomography angiography and d) magnetic resonance pulmonary angiography demonstrate attenuated pulmonary vasculature (arrows) with calcified mediastinal lymph nodes (arrowhead).

FIGURE 3

A 45-year-old with pulmonary hypertension. a, b) Dual-energy computed tomography pulmonary angiography and c) corresponding magnetic resonance pulmonary angiography confirm chronic thromboembolic pulmonary hypertension. There is dilatation of the main pulmonary artery (PA), dilated right atrium (RA) and right ventricle (RV) with right ventricular hypertrophy, eccentric thrombus in right lower lobe and left main pulmonary artery (arrows), multiple segmental perfusion defects (*), proximal pulmonary arterial stenosis and webs (arrowheads).

FIGURE 4

a) Magnetic resonance and b) catheter pulmonary angiography and c) computed tomography and d) catheter pulmonary angiography in two different cases of chronic thromboembolic pulmonary hypertension. There is good disease correlation on all three modalities, e.g. pouch defect on magnetic resonance image (arrows) and proximal stenosis in left lower lobe artery (arrowhead).

FIGURE 5

A 50-year-old male with persistent abnormality on computed tomography (CT) despite anticoagulation for 1 year. a) CT scan showing an expansile low attenuation lesion in the right main pulmonary artery (arrow); b) ¹⁸F-fluorodeoxyglucose positron emission tomography with corresponding high uptake in keeping with pulmonary artery sarcoma. Note mediastinal soft tissue with increased uptake.