History
A 68-year-old female patient, who had undergone a balloon pulmonary angioplasty (BPA) four months ago, returned to the hospital for her second scheduled treatment session. She had been suffering from chronic thromboembolic pulmonary hypertension (CTEPH) for the past 8 years and, at admission she reported exertional dyspnea and asymmetrical edema of both legs. A right heart catheterization measured a mean pulmonary artery pressure (mPAP) of 46 mmHg and a pulmonary vascular resistance (PVR) of 926 dyn·s·cm-5. A dual energy (DE) chest CT was requested to evaluate the lung perfused blood volume (LungPBV) and the pulmonary arteries prior to treatment.
Diagnosis
CT images showed dilation of the central pulmonary arteries (PA), tapering of the peripheral PA, cardiomegaly with significant enlargement of the right atrium and ventricle, along with a mosaic pattern of attenuation in the lungs. These findings are consistent with a severe chronic pulmonary hypertension. In the DE assessment of LungPBV, multiple peripheral wedge-shaped perfusion defects, dorsal and ventral, were evident bilaterally. An aberrant right subclavian artery (ARSA), originating directly from the aortic arch and distal to the left subclavian artery, was also seen. Subsequently, the patient underwent BPA with a good outcome. The mPAP was reduced to 35 mmHg, and the PVR to 582 dyn·s·cm-5. Her dyspnea had significantly improved and the edema in her legs subsided.
Courtesy of Department of Radiology, Affiliated Beijing Chaoyang Hospital of Capital Medical University, Beijing, P. R. China
Fig. 1: Cinematic VRT images demonstrate dilation of the central PA and tapering of the peripheral PA (Fig. 1a), as well as an ARSA originating directly from the aortic arch and distal to the left subclavian artery (Fig. 1b, arrow).
Courtesy of Department of Radiology, Affiliated Beijing Chaoyang Hospital of Capital Medical University, Beijing, P. R. China
Fig. 2: Two axial images (Figs. 2a & 2c, lung window) show bilateral mosaic attenuations. LungPBV images in corresponding axial views (Figs. 2b & 2d) and bilateral sagittal views (Fig. 2c – right lung, Fig. 2d – left lung) show multiple peripheral wedge-shaped perfusion defects, dorsal and ventral. Dilation of the pulmonary trunk and cardiomegaly are also seen.
Comments
CTEPH is defined as an increase in the mPAP to more than 25 mmHg with persistent perfusion deficits or vascular lesions after three months of anticoagulation therapy. It is often first diagnosed at a very late stage as the patients usually experience only nonspecific symptoms such as progressive exertional dyspnea. At present, ventilation/perfusion scintigraphy is recommended for the screening of patients with pulmonary hypertension and indication of CTEPH. However, studies have shown promising agreement between DECT LungPBV and scintigraphy in assessment of the pulmonary vascular bed. [1] [2] Other features including shorter scan time, visualization and quantification of regional lung perfusion, as well as anatomical information and vascular findings with better spatial resolution are also considered as advantages of DECT. An early recognition of CTEPH is of paramount importance, since chronic thromboembolism is potentially curable with pulmonary endarterectomy (PEA). If the patient is not suitable for PEA, then BPA is considered, such as in this case. CTEPH has a poor prognosis when left untreated, leading to right heart failure as a result of progressive right ventricular dysfunction. DECT could contribute to the diagnosis of CTEPH for patients who can tolerate the administration of contrast media and serve as an alternative imaging examination when scintigraphy cannot be performed.
Examination Protocol