Summary of techniques used in the diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH)
| Technique | Advantages | Potential disadvantages |
| Ventilation/perfusion (V′/Q′) scan | Essential for diagnosing CTEPH | Can give intermediate probability result, |
| Sensitivity >96% | which cannot rule out CTEPH | |
| Negative result rules out CTEPH | May underestimate the burden | |
| Can distinguish between large-vessel occlusive and small-vessel pulmonary vascular disease | of vascular obstruction | |
| Less radiation exposure than CTPA | ||
| Less likely than other techniques to detect incidental findings | ||
| Avoids potential problems with intravenous contrast | ||
| Conventional pulmonary angiography (CPA) | Can be combined with RHC to provide imaging and haemodynamic information | Invasive |
| Right heart catheterisation (RHC) | Mandatory in diagnosing CTEPH | Invasive |
| Essential measurements of mean arterial pressure and pulmonary capillary wedge pressure | ||
| Information on disease severity, right heart function, mixed venous oxygen saturation | ||
| Computed tomography pulmonary angiography (CTPA) | Noninvasive | Sensitivity 51% (lower than V′/Q′ scan) |
| High-resolution images | Chronic disease looks different to acute PE: | |
| New scanners can provide multi-planar and three-dimensional reconstructions of the vascular tree More anatomical detail than MRI: information about vascular wall thickness and surrounding structures not appreciable with CPA No need for direct catheter access | additional training required Risk of false positives (e.g. pulmonary artery sarcoma) May miss disease in distal segmental or subsegmental vessels May miss inoperable patients who could | |
| Can reveal associated findings, e.g. bronchial artery collaterals, mosaic perfusion patterns | begin medical therapy May underestimate clot burden | |
| Lower cost than CPA | ||
| Rapid acquisition, even in breathless patients | ||
| DECTA has improved the detection of distal CTEPH | ||
| Cardiac magnetic resonance imaging (MRI) | Noninvasive, no radiation exposure | Limited availability, expensive, |
| Morphological, functional and anatomical assessment of heart and pulmonary circulation | time consuming | |
| Useful for repeat studies, e.g. pre- and post-operative monitoring | ||
| Phase-contrast MRI can quantify blood flow and peak velocity in the main pulmonary artery | ||
| Contrast-enhanced magnetic resonance angiography has similar sensitivity to CTPA |
PE: pulmonary embolism; DECTA: dual-energy computed tomography angiography. Information from [14, 17, 18].