Table 1.

Salient features of conditions mimicking CTEPH.

	CTEPH Mimic	Similarities on imaging tests	Dissimilarities on imaging tests	Conditions in which the mimic should certainly be considered
1	In situ thrombosis in congenital heart disease	Mosaic attenuation seen but less pronounced Bronchial collaterals seen but less common Central pulmonary artery thrombus	Gross disproportionate enlargement of the central pulmonary arteries Absence of other vascular signs, such as vascular webs, vessel beading or paucity of peripheral arteries, beyond the central pulmonary arteries VQ scan normal or mottled appearance	Patients with congenital heart disease Eisenmenger's physiology
2	Pulmonary artery sarcoma	Perfusion defects on VQ scan Pulmonary arterial intraluminal filling defect	Complete vessel occlusion Expansile mass Extraluminal extension Involvement of pulmonary valve and RVOT Heterogenous attenuation PET avidity Delayed enhancement on CTA and MRI	Increase in thrombus size despite anticoagulation Pulmonary nodules Movement with cardiac cycle
3	Pulmonary vein involvement: a) Fibrosing mediastinitis b) Pulmonary vein stenosis secondary to ablation for atrial fibrillation	a) Mismatched perfusion defects on VQ scan b) Mismatched perfusion defects on VQ scan	a) Mediastinal and hilar soft tissue masses Mediastinal calcification Central pulmonary artery stenosis Pulmonary venous stenosis Airway narrowing Mediastinal lymphadenopathy b) Filling defects in the pulmonary veins Interlobulat septal thickening, pleural effusions, Kerley B lines on CXR	a) Prior history of histoplasmosis History of recurrent pulmonary infections b) Prior history of ablation for atrial fibrillation
4	PVOD	Mosaic attenuation pattern in lung fields	VQ scan normal in most cases Smooth interlobular septal thickening Ground glass opacities Mediastinal lymphadenopathy	Development of pulmonary edema following pulmonary vasodilator therapy
5	Large vessel vasculitis	Collateralization of vessels	Abnormal aortic contour and mural thickening Pulmonary aneurysms Transmural arterial calcification Absent intraluminal thrombus PET avidity	Asian women (Takayasu's arteritis) Visual defects, limb claudication, fever Concomitant presence of stroke, myocardial ischemia
6	Sarcoidosis	Mismatched perfusion defects on a VQ scan Arterial webbing Intimal irregularities Vascular narrowing with post stenotic dilatation	Absence of filling defects in the pulmonary arteries Parenchymal involvement Upper lobe predominance Mediastinal lymphadenopathy causing extrinsic compression	Evidence of sarcoidosis in extra pulmonary organs
7	Malignancy	VQ scan with multiple mismatched perfusion defects	Lymphangitic carcinomatosis PET avidity in some cancers	Significant unintentional weight loss Current or prior malignancy Evidence of metastatic disease Mediastinal lymphadenopathy
8	Congenital anomalies of the pulmonary artery: a) Congenital proximal interruption of the pulmonary artery b) Peripheral pulmonary artery stenosis	a) Unilateral lung volume loss Mismatched perfusion defect on VQ scan b) Mismatched perfusion defects	a) Smooth abrupt cut off of the pulmonary artery within 1 cm of the hilum on CTA Unilateral perfusion defect on VQ scan Absence of findings of pulmonary hypertension b) Congenital anomaly Can be seen in Noonan's, Alagille's or William's syndromes	Presence of other cardiac anomalies

CTEPH: chronic thromboembolic pulmonary hypertension, VQ: ventilation perfusion, RVOT: right ventricular outflow tract, PET: positron emission tomography, CTA: computed tomographic angiography, MRI: magnetic resonance imaging, CXR: chest xray, PVOD: pulmonary veno-occlusive disease