Abstract
Chronic thromboembolic pulmonary hypertension (CTEPH) is caused by mechanical obstruction of large pulmonary arteries secondary to one or more episodes of pulmonary embolism. Ventilation perfusion scan is the recommended initial screening test for this condition and typically shows multiple large mismatched perfusion defects. However, not all patients with an abnormal ventilation perfusion scan have CTEPH since there are other conditions that be associated with a positive ventilation perfusion scan. These conditions include in situ thrombosis, pulmonary artery sarcoma, fibrosing mediastinitis, pulmonary vasculitis and sarcoidosis, among others. Although these conditions cannot be distinguished from CTEPH using a ventilation perfusion scan, they have certain characteristic radiological features that can be demonstrated on other imaging techniques such as computed tomography scan and can help in differentiation of these conditions. In this review, we have summarized some key clinical and radiological features that can help differentiate CTEPH from the CTEPH mimics.
Highlights
Chronic thromboembolic pulmonary hypertension (CTEPH) is caused by mechanical obstruction of major pulmonary arteries due to one or recurrent pulmonary thromboemboli, which is followed by organization of the thrombus and small vessel arteriopathy.[1,2]
Due to progressive right-sided pressure and volume overload from the shunting, there is increase in shear stress which leads to endothelial dysfunction and progressive vascular remodeling; shunt reversal develops over time leading to Eisenmenger’s physiology
Pulmonary artery sarcoma (PAS) presents as a heterogeneously enhancing low-attenuation filling defect frequently occupying the entire diameter of the pulmonary artery trunk or the main pulmonary arterial branches (Fig. 3) causing expansion of the involved arteries, invasion of the tumor into the pulmonary arterial wall, and extravascular tumor extension.[19,22]
Summary
Chronic thromboembolic pulmonary hypertension (CTEPH) is caused by mechanical obstruction of major pulmonary arteries due to one or recurrent pulmonary thromboemboli, which is followed by organization of the thrombus and small vessel arteriopathy.[1,2] It is an important reversible cause of pulmonary hypertension (PH), which is frequently underdiagnosed.[1]. The exact mechanism behind thrombus formation is poorly understood, but it has been hypothesized that multiple factors may play a role These include shear stress on the vessel wall, chronic stasis in the aneurysmal pulmonary dilations, increase in blood viscosity, chronic hypoxemia and endothelial damage.[9,11,12] In congenital heart diseases, due to progressive right-sided pressure and volume overload from the shunting, there is increase in shear stress which leads to endothelial dysfunction and progressive vascular remodeling; shunt reversal develops over time leading to Eisenmenger’s physiology. PAS presents as a heterogeneously enhancing low-attenuation filling defect frequently occupying the entire diameter of the pulmonary artery trunk or the main pulmonary arterial branches (Fig. 3) causing expansion of the involved arteries, invasion of the tumor into the pulmonary arterial wall, and extravascular tumor extension.[19,22] While these findings are non-specific and can Pulmonary Circulation Volume 10 Number 1 | 3
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