44
. CT FINDINGS IN DISEASES ASSOCIATED WITH PULMONARY HYPERTENSION k.s.suneetha 1 st yr P.G G.S.L

Pulmonary hypertension , dr.k.s.suneetha

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Page 1: Pulmonary hypertension , dr.k.s.suneetha

.

CT FINDINGS IN DISEASES ASSOCIATED WITH PULMONARY HYPERTENSION

k.s.suneetha 1st yr P.G

G.S.L

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Abstract•Pulmonary hypertension primarily affect arterial (precapillary) or the venous (postcapillary) pulmonary circulation.

•Pulmonary arterial hypertension may be :• idiopathic or •arise in association with chronic pulmonary thromboembolism; •pulmonary embolism caused by tumor cells,• parasitic material, or• foreign material; •parenchymal lung disease; •liver disease; vasculitis;• human immunodeficiency virus infection; or• a left-to-right cardiac shunt..

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•Features of pulmonary arterial hypertension that may be seen at computed tomography (CT) are

•central pulmonary artery dilatation the diameter of which frequently exceeds that of the ascending aorta

•dilatation of the right and left main pulmonary arteries

• abrupt narrowing or tapering of peripheral pulmonary vessels

•right ventricular hypertrophy

•right ventricular and atrial enlargement with inversion of the interventricular septum and dilatation of the tricuspid valve annulus .

•dilated bronchial arteries, and

• a mosaic pattern of attenuation due to variable lung perfusion.

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•. Pulmonary venous hypertension may result from •pulmonary veno-occlusive disease• pulmonary venous compression by extrinsic lesions (eg, mediastinal fibrosis), left-sided cardiac disease, or pulmonary vein stenosis.

•CT scan shows• pulmonary interstitial and alveolar edema with signs of pulmonary arterial hypertension.• High-resolution CT with standard axial and angiographic acquisitions is useful for identifying underlying disorders and differentiating among the various causes of secondary pulmonary hypertension.

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Introduction•Pulmonary hypertension is hemodynamically defined as a mean pulmonary artery pressure greater than 25 mm Hg at rest or greater than 30 mm Hg during exercise with an increased pulmonary vascular resistance .

• The diagnosis is based on a clinical assessment of hemodynamic parameters, medical history, results of pulmonary function testing, and radiological and histological findings.

• High-resolution computed tomography (CT) and CT angiography play a crucial role in the diagnostic work-up and are particularly important for identifying patients with chronic or recurrent pulmonary thromboembolism and for assessing the feasibility of pulmonary thromboendarterectomy .

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Pulmonary Arterial Hypertension

•In CT- distal main pulmonary artery diameter greater than or equal to 29 mm at its widest point has a positive predictive value of more than 95% and a specificity of 89%.

• and diameter exceeding that of the ascending aorta has a positive predictive value of more than 95% and a specificity of more than 90%, for a diagnosis of pulmonary arterial hypertension .

• Pulmonary arterial hypertension can be reliably predicted when (a) the CT-demonstrated diameter of the distal main pulmonary artery is greater than or equal to 29 mm and the segmental artery-to-bronchus ratio is greater than 1:1 in three of four pulmonary lobes (specificity, 100%) or

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•b.the ratio of the CT-demonstrated distal main pulmonary artery diameter to the aortic diameter is greater than 1:1, particularly in patients younger than 50 years .

•In a recently published ECG-gated multidetector CT study found that of all the ECG-gated CT parameters evaluated, right pulmonary artery wall distensibility, defined by the change in cross-sectional area between diastole and systole, was the most reliable parameter for identifying patients with pulmonary hypertension and showed the strongest correlation to mean pulmonary artery pressure.

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•Systolic right ventricular outflow tract diameter and cross-sectional area were found to differ significantly between patients with pulmonary hypertension and patients without it

•, whereas the diastolic values were not significantly different (10). These findings suggest that the measurement of right pulmonary artery wall distensibility at ECG-gated CT may help improve the accuracy of CT-based diagnoses of pulmonary hypertension and that the measurement of diastolic right ventricular outflow tract wall thickness, which correlates with the mean pulmonary artery pressure and is potentially reversible, may be useful in patients referred for CT evaluation of pulmonary hypertension.

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•Complications detectable with CT include :

•central pulmonary artery thrombosis,• premature atherosclerosis of the pulmonary arteries, •pulmonary artery dissection,•right heart chamber hypertrophy and dilatation .

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Idiopathic Pulmonary Arterial Hypertension• is a subtype of pulmonary arterial hypertension without an identifiable cause.

•disease of young adulthood, occurring most often in those between the ages of 20 and 45 years .

•Women are more commonly affected than men ).

• The clinical manifestations are nonspecific and may include exertional dyspnea (60% of all cases), fatigue, angina, syncope, and cor pulmonale

• The average delay between the onset of symptoms and the diagnosis of idiopathic pulmonary arterial hypertension is 2 years.

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•CT features:•central pulmonary artery dilatation, usually in the absence of detectable intraluminal thrombi;

•small tortuous peripheral vessels representing plexogenic arteriopathy; and

•an abrupt decrease in the caliber of segmental and subsegmental arteries

•Wall-adherent apposition thrombi may form in the central pulmonary arteries in severe cases and usually are accompanied by massive enlargement of the pulmonary artery trunk and the right and left main pulmonary arteries .

•Additional CT findings may include right heart enlargement, pericardial effusion, and a mosaic pattern of attenuation in lung parenchyma..

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) Axial contrast-enhanced CT scan obtained at initial presentation shows central pulmonary artery dilatation with aneurysmal enlargement of the left lower lobe pulmonary artery (*) but no evidence of intraluminal thrombi.

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) Axial contrast-enhanced CT scan obtained 2 years later shows wall-adherent apposition thrombi (arrowheads) with recanalization (arrows) in the pulmonary artery trunk and the right main pulmonary artery. The left lower lobe pulmonary artery (*) remains enlarged.

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) Axial contrast-enhanced CT scan obtained at the level of the apical segment of the lower lobes shows corkscrewlike peripheral pulmonary arteries (arrows), findings indicative of plexogenic arteriopathy.

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•the pattern seen in idiopathic pulmonary arterial hypertension often is characterized by focal perivascular hyperattenuating areas in a peripheral or perihilar distribution (Fig 2 ) or small, scattered, well-defined areas of low attenuation corresponding to the anatomic unit of a secondary pulmonary lobule with adjacent areas of increased attenuation in a patchy and diffuse distribution (11).

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Pulmonary Arterial Hypertension Due to Chronic Thrombotic and/or Embolic Disease

•Pulmonary arterial hypertension may be caused by• thrombotic or

• thromboembolic obstruction of the pulmonary arteries (as in CTEPH or sickle cell disease) or by nonthrombotic embolic obstruction of the pulmonary vascular bed, which may be due to tumor emboli (originating from gastric carcinoma, carcinoma of the breast or prostate, hepatocellular carcinoma, malignant melanoma, choriocarcinoma, ovarian carcinoma, or right atrial myxoma), parasitic emboli (commonly produced by Schistosoma mansoni), or foreign material emboli.

• Fat emboli, amniotic fluid emboli, and septic pulmonary emboli rarely produce clinically significant pulmonary arterial hypertension (7

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CT Features of CTEPH•classified as vascular or •parenchymal changes.

• Vascular changes include signs of pulmonary arterial hypertension (central pulmonary artery dilatation, right heart chamber enlargement, atherosclerotic plaques), chronic pulmonary thromboembolism (complete or partial thromboembolic obstruction, bands or webs in the pulmonary arteries), and a systemic collateral supply.

•Parenchymal changes include mosaic lung perfusion and peripheral parenchymal opacities

•Directly visualized intraluminal thrombi in the pulmonary arteries are the vascular CT finding with the highest specificity for a diagnosis of CTEPH

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•The spectrum of CT findings that are due to partial vascular obstruction includes

• thickening of the pulmonary arterial wall;

•an irregular contour of the intimal surface; and

• intraluminal bands, webs, and wall-adherent soft-tissue formations, which may be masslike, interposed between the intimal surface and the column of contrast-enhanced blood .

• At conventional angiography, complete vascular obstruction appears as a convex margin of the contrast material bolus. This feature, which has been described as a “pouch defect,” is difficult to detect on axial CT sections .

•an abrupt decrease in vessel diameter and the absence of contrast material in the vessel segments distal to the obstruction .

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• CT scans viewed at lung window settings demonstrate segmental and subsegmental vessels with diameters that are abnormally narrowed in comparison with the diameters of the accompanying bronchi, abrupt vessel cut-offs, and marked variation in the size of segmental vessels (35). Findings of disparity in the size of segmental vessels and mosaic lung attenuation reliably distinguish CTEPH from nonthromboembolic pulmonary arterial hypertension (19). Mild pericardial thickening or pericardial effusion may be seen in patients with severe CTEPH (17). Lymph node enlargement is common and

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) Axial contrast-enhanced CT scan shows an eccentric wall-adherent thrombus (arrow) in the right interlobar pulmonary artery and extending into the right upper and lower lobe pulmonary arteries, producing an irregular contour of the intimal surface

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) Axial contrast-enhanced CT scan obtained at the level of the lower lobes shows right atrial and ventricular enlargement with an inverted interventricular septum, right ventricular hypertrophy, and an eccentric chronic thrombus causing a crescent-shaped intraluminal filling defect (arrow) in the left lower lobe pulmonary artery. There are multiple small filling defects in the subsegmental branches of both lower lobes

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Axial contrast-enhanced CT scan obtained in a 61-year-old woman with a systolic pulmonary artery pressure of 80 mm Hg shows a common pattern of mosaic lung attenuation, with segmental and subsegmental perfusion defects

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Pulmonary Arterial Hypertension Associated with Lung Disease•Lung disease is the most common cause, and the presence of pulmonary hypertension in this setting is an unfavorable prognostic sign

•Patients typically present with signs and symptoms related to the specific underlying disease.

•Restrictive lung diseases associated with pulmonary hypertension include idiopathic interstitial pneumonias (eg, idiopathic pulmonary fibrosis, in which pulmonary hypertension is reported to occur with a prevalence as high as 46%) ( ); secondary interstitial pneumonias due to connective tissue disease, sarcoidosis ), vasculitis, drug toxicity, and exposure to various environmental toxins; and a heterogeneous group of conditions such as thoracic cage deformities (due to kyphoscoliosis, thoracoplasty, or restrictive pleural disease), diaphragmatic disorders, neuromuscular diseases, and spinal cord injuries.

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) Axial contrast-enhanced CT scan shows massive dilatation of the pulmonary artery trunk and the right main pulmonary artery

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) Axial contrast-enhanced CT scan (lung window settings) shows severe emphysema with multiple bullae and blebs, decreased vascularity, and loss of lung parenchyma. A subtle mosaic attenuation pattern is visible, with areas of hyperattenuation (arrows) indicative of blood flow redistribution to relatively preserved lung regions.

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Pulmonary Arterial Hypertension Associated with Cardiac Disease

•Pulmonary arterial hypertension due to

• sustained cardiac left-to-right shunt and shunt reversal (Eisenmenger syndrome)

• congenital cardiac abnormalities such as ventricular septal defect, atrial septal defect and patent ductus arteriosus.

• transposition of the great arteries •

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Axial contrast-enhanced CT scan shows a right-to-left cardiac shunt caused by a large atrial septal defect.

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) Axial contrast-enhanced CT scan obtained at the level of the carina shows moderate dilatation of the pulmonary artery trunk and the right and left main pulmonary arteries. The lung parenchyma (not shown) had a normal appearance

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Pulmonary Hypertension Associated with Arteriovenous Shunts•Pulmonary arteriovenous malformations may occur sporadically but are most commonly seen in association with Osler-Weber-Rendu disease (hereditary hemorrhagic telangiectasia), an autosomal dominant disorder that is characterized by cutaneous and mucosal telangiectasia and arteriovenous malformations in other organs (5).

• Diffuse pulmonary arteriovenous shunting also is seen in pregnancy, polysplenia syndrome, liver cirrhosis, and complex cardiac malformations .

• Untreated or occult arteriovenous malformations may increase in size over time, causing a hyperdynamic circulatory status with severe hypoxemia due to high shunt volumes, with the eventual development of pulmonary hypertension.

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•CT in combination with a mosaic pattern of lung perfusion , an appearance produced by secondary small-vessel arteriopathy or by thromboembolic obstruction of the pulmonary arteries because of emboli originating in or passing through arteriovenous connections.

• Other frequent CT findings include small, rounded parenchymal opacities in the lung periphery with a dilated, tortuous feeding artery and an enlarged draining vein, features that represent CT-detectable macroscopic arteriovenous shunts ).

•Diffuse macroscopic arteriovenous shunting typically manifests at CT as dilatations of the pulmonary arteries and veins with a weblike, reticular vascular pattern in the lung periphery and centrilobular vessel-associated micronodules connected by arcadelike, dilated vascular branches.

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Axial contrast-enhanced CT scan shows massive right atrial and ventricular enlargement and an inverted interventricular septum

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) Axial contrast-enhanced CT scan obtained at the level of the carina shows a mosaic perfusion pattern consisting of sharply demarcated regions of decreased parenchymal attenuation with reduced vessel diameters and adjacent regions of increased parenchymal attenuation. The pulmonary artery trunk and the left main pulmonary artery are markedly dilated

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Axial contrast-enhanced CT scan shows multiple hyperattenuating nodular features suggestive of hepatic arteriovenous malformations; enlarged hepatic arteries; and early enhancement of the hepatic veins (arrowheads) during the arterial phase, an effect of arteriovenous shunting.

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Pulmonary Venous Hypertension•caused by compromised pulmonary venous drainage , mediastinal fibrosis (which may affect the arterial circulation, as well), •pulmonary veno-occlusive disease, or• an extrinsic lesion compressing the pulmonary veins.• Other causes include a left atrial neoplasm,• mitral valve stenosis,• left ventricular failure, and ,• congenital venous stenosis or• an anomalous venous connection •The characteristic CT features of pulmonary venous hypertension are interlobular septal thickening, pleural effusion, and, occasionally, airspace opacities.• Evidence of coexistent pulmonary arterial hypertension due to retrograde transmission of elevated venous pressures across the capillary bed

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• Pulmonary Venous Hypertension Associated with Cardiac Disease

• frequently caused by left-sided cardiac disorders such as left ventricular failure, its most common cause both in adults and in children.

• Less frequent causes are left atrial thrombus, left atrial neoplasm (myxoma, sarcoma, or metastasis), mitral stenosis, and congenital cardiac anomalies

• Left-sided cardiac disease may display imaging features similar to those of pulmonary veno-occlusive disease. The distinguishing feature is left atrial enlargement, which is frequently seen in left-sided cardiac disease but not in pulmonary veno-occlusive disease

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Axial contrast-enhanced CT scan shows discrete interlobular septal thickening and multiple ill-defined centrilobular ground-glass opacities, findings indicative of interstitial and early alveolar edema. The central pulmonary veins (arrows) appear narrowed

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Axial contrast-enhanced CT scan obtained at the level of the carina shows a dilated main pulmonary artery and mediastinal lymphadenopathy. The CT-based diagnosis of pulmonary veno-occlusive disease was confirmed by hemodynamic measurements and histologic findings.

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• Pulmonary Veno-occlusive Disease• The condition primarily affects children, distributed equally between the

sexes, and young adults ).• Its etiology is unknown. • Clinical associations with high estrogen levels during pregnancy, oral

contraceptive use, viral infection, bone marrow transplantation, and drug (eg, bleomycin, mitomycin) toxicity have been described .

• Patients present with slowly progressive dyspnea and episodes of acute pulmonary edema, sometimes complicated by hemoptysis (4).

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• At CT, the combination of features

• features of pulmonary arterial hypertension with interstitial and alveolar edema is virtually diagnostic of pulmonary veno-occlusive disease.

• CT scans show markedly small central pulmonary veins, interlobular septal thickening, and patchy centrilobular ground-glass opacities representing interstitial and alveolar edema .

• Additional CT findings include dilatation of the central pulmonary arteries, right ventricular enlargement, a normal-sized left atrium, pleural effusion, and mediastinal lymphadenopathy .

• The diagnosis is based on a combination of anatomic findings at CT and hemodynamic findings at cardiac catheterization with conventional angiographic evidence of delayed filling of small pulmonary veins; however, histologic analysis may be necessary to confirm the diagnosis .

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• Conclusions

• Pulmonary hypertension is a frequent clinical diagnosis associated with high patient morbidity and mortality.

• Diseases that can induce pulmonary hypertension display a wide spectrum of partially overlapping CT features, and definitive diagnosis may require correlation of CT imaging findings with clinical, histopathologic, and angiographic findings.

• To allow appropriate therapeutic management, awareness of the various disease entities associated with pulmonary hypertension and knowledge of the entire spectrum of their imaging features are essential.

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