State-of-the-art imaging techniques in chronic thromboembolic pulmonary hypertension.

It is important to differentiate chronic thromboembolic pulmonary hypertension (CTEPH) from other forms of pulmonary hypertension (PH) to target treatment and optimize therapeutic outcome. Misdiagnosis is common, and high-quality imaging is essential if CTEPH is to be diagnosed correctly. In addition to making a diagnosis, imaging helps identify patients for surgery, aids surgical planning, and provides postsurgical monitoring. Ventilation-perfusion scintigraphy and pulmonary angiography have been the mainstay of diagnosis and surgical assessment for many years, but cross-sectional techniques are rapidly taking over. Echocardiography is used to confirm or refute the presence of PH and to identify cardiac causes if PH is present. For patients with PH but no evidence of cardiac disease, multislice computed tomography (CT) is the next best step. CT distinguishes CTEPH from idiopathic arterial PH, evaluates underlying lung disease, and may help identify rarer causes of PH. CT is quick, widely available, and inexpensive. There is, however, a significant radiation burden, and it is unsuitable for serial examinations. Magnetic resonance (MR) involves no ionizing radiation and makes an ideal alternative. When combined with techniques for measuring ventricular function and blood flow, MR provides unique insight into structure and function. CT and MR are complementary techniques, and together they represent the future of imaging in PH. How they might be used in routine clinical practice is presented as a diagnostic algorithm developed at Papworth Hospital, the United Kingdom's national center for surgical treatment of CTEPH.