DOI: 10.1148/rg.23si035504
(Radiographics. 2003;23:S167-S180.)
© RSNA, 2003
CT and MR Imaging of Pericardial Disease1
Zhen J. Wang, MD,
Gautham P. Reddy, MD, MPH,
Michael B. Gotway, MD,
Benjamin M. Yeh, MD,
Steven W. Hetts, MD and
Charles B. Higgins, MD
1 From the Department of Radiology, Box 0628, University of California, San Francisco, 505 Parnassus Ave, San Francisco, CA 94143-0628. Presented as an education exhibit at the 2002 RSNA scientific assembly. Received February 3, 2003; revision requested April 29 and received June 30; accepted July 2. Address corresponcence to G.P.R. (e-mail: gautham.reddy@radiology.ucsf.edu).
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Abstract
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In the evaluation of pericardial disease, computed tomography (CT) and magnetic resonance (MR) imaging traditionally have been used as adjuncts to echocardiography. However, CT and MR imaging are particularly useful as sensitive and noninvasive methods for evaluating loculated or hemorrhagic pericardial effusion, constrictive pericarditis, and pericardial masses. Both CT and MR imaging provide excellent delineation of the pericardial anatomy and can aid in the precise localization and characterization of various pericardial lesions, including effusion, constrictive pericarditis and pericardial thickening, pericardial masses, and congenital anomalies such as partial or complete absence of the pericardium. Both modalities provide a larger field of view than does echocardiography, allowing the examination of the entire chest and detection of associated abnormalities in the mediastinum and lungs. Soft-tissue contrast on CT scans and MR images also is superior to that on echocardiograms. Given the many potential applications of these modalities in the evaluation of pericardial diseases, familiarity with the CT and MR imaging features of these diseases is important.
© RSNA, 2003
Index Terms: Heart, MR, 50.1214, 55.1214 • Mediastinum, MR, 60.1214 • Pericarditis, 55.824 • Pericardium, fluid, 55.82 • Pericardium, abnormalities, 55.194, 55.30, 55.41 • Pericardium, CT, 55.1211
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Introduction
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The pericardium is a two-layered membrane that envelops all four cardiac chambers and the origins of the great vessels. The parietal and visceral layers are separated by a small amount of serous fluid—normally, about 15–50 mL—that is mainly an ultrafiltrate of plasma (1). The pericardium limits the spread of infection and inflammation from adjacent mediastinal structures and is thought to prevent excessive dilatation of the heart and to reduce friction between the heart and surrounding structures (2). Many disease processes can affect the pericardium, including infection, neoplasm, trauma, primary myocardial disease, and congenital disease. In this article, the characteristic imaging features of various pericardial diseases are reviewed, and the advantages and limitations of various modalities for the evaluation of pericardial diseases are discussed.
Echocardiography is the imaging modality most often used for the initial evaluation of pericardial disease, especially in patients suspected of having pericardial effusion or tamponade. Echocardiography is readily available and does not involve ionizing radiation. However, the restricted acoustic window limits the usefulness of this modality for imaging of the entire pericardium. Loculated pericardial effusions, especially those in unusual locations, can be difficult to diagnose with echocardiography (3). Routine transthoracic echocardiography is not highly accurate for the detection of pericardial thickening associated with pericarditis (4). Transesophageal echocardiography has shown more promise but is limited by the narrow field of view (5).
Computed tomography (CT) and magnetic resonance (MR) imaging offer distinct advantages in the imaging of the pericardium. Both modalities provide a larger field of view than does echocardiography, thus allowing the examination of the entire chest and detection of associated abnormalities in the mediastinum and lungs. Soft-tissue contrast on CT scans and MR images is superior to that on echocardiograms. CT and MR imaging provide excellent anatomic delineation and enable precise localization of pericardial masses. In addition, CT and MR imaging are performed in standard imaging planes and do not require use of a transducer; therefore, they are less operator dependent than echocardiography.
Multidetector CT enables motion-free imaging of the pericardium, as well as multiplanar reformation of images for better visualization of any pericardial disease. CT attenuation measurements also provide tissue characterization of some masses. Another advantage of CT over other modalities is the ability to detect pericardial calcification—a finding indicative of constrictive pericarditis in patients with constrictive or restrictive physiologic features. Disadvantages of CT include the use of intravenously administered iodinated contrast material and of ionizing radiation. If CT is performed without electrocardiographic (ECG) gating or triggering, as is often the case, then cardiac motion artifacts can limit evaluation of the pericardium. Another limitation of CT imaging of the pericardium is the occasional difficulty in differentiating fluid from thickened pericardial tissue.
MR imaging can provide comprehensive depiction of the pericardium without the use of either iodinated contrast material or ionizing radiation. Another advantage of MR imaging over CT and echocardiography is its superior ability to characterize pericardial effusions and pericardial masses with the use of a combination of T1-weighted, T2-weighted, and gradient-recalled echo (GRE) cine sequences. A disadvantage of using MR imaging with ECG gating is that arrhythmia, which is associated with pericardial diseases, can cause artifacts.
CT or MR imaging should be used when findings at echocardiography are nondiagnostic or difficult to interpret or when loculated or hemorrhagic pericardial effusion and pericardial thickening are suspected. CT and MR imaging also are useful for further characterization of pericardial masses detected at echocardiography.
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Normal Anatomy
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CT and MR imaging provide excellent visualization of the pericardium in most patients (6,7). The thickness of the normal pericardium, measured on CT scans and on MR images, is less than 2 mm (Fig 1) (8,9). Discrimination of the pericardium from the myocardium on radiologic images requires the presence of epicardial fat or pericardial fluid. Although the pericardium is visible over the right atrium and right ventricle in most individuals, it often is not visible over the lateral and posterior walls of the left ventricle. The left atrium is only partially covered by the pericardium; it has been suggested that this anatomic feature may contribute to the left atrial enlargement seen in patients with constrictive pericarditis (10). Several pericardial recesses may be visible on CT scans and MR images (11,12). Small amounts of fluid may be present in these structures in healthy individuals. The superior pericardial recess, a curvilinear structure wrapped around the right wall of the ascending aorta, may be mistaken for an aortic dissection, mediastinal mass, lymph node, or thymus (13–15) (Fig 2). The transverse pericardial sinus, which is dorsal to the ascending aorta, sometimes may be mistaken for aortic dissection or lymphadenopathy (16,17). The oblique pericardial sinus, which is situated behind the left atrium, may be misinterpreted as esophageal lesions or bronchogenic cysts (11). Knowledge of the locations of these recesses can help the imaging specialist differentiate them from abnormal lesions.
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Figure 1a. Normal pericardium. Axial contrast-enhanced CT scan (a) and axial ECG-gated spin-echo (SE) MR image (b) show a pericardium with normal thickness (arrows). Note the epicardial and anterior mediastinal fat outlining the pericardium in b.
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Figure 1b. Normal pericardium. Axial contrast-enhanced CT scan (a) and axial ECG-gated spin-echo (SE) MR image (b) show a pericardium with normal thickness (arrows). Note the epicardial and anterior mediastinal fat outlining the pericardium in b.
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Figure 2a. Normal superior pericardial recess. Axial contrast-enhanced CT scan (a) and ECG-gated SE image (b) show the superior pericardial recess (arrows) in a normal position, posterior to the ascending aorta.
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Figure 2b. Normal superior pericardial recess. Axial contrast-enhanced CT scan (a) and ECG-gated SE image (b) show the superior pericardial recess (arrows) in a normal position, posterior to the ascending aorta.
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Pericardial Effusion
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Pericardial effusion originates in the obstruction of venous or lymphatic drainage from the heart. Common causes of pericardial effusion include heart failure, renal insufficiency, infection (bacterial, viral, or tuberculous), neoplasm (carcinoma of lung or breast, or lymphoma), and injury (from trauma or myocardial infarction).
Echocardiography is considered the primary imaging modality for the evaluation of pericardial effusion because of its high sensitivity and specificity, lack of ionizing radiation, and low cost. CT and MR imaging are indicated when loculated or hemorrhagic effusion or pericardial thickening is suspected (8,18) or when findings at echocardiography are inconclusive. Loculated effusions, especially those in anterior locations, can be difficult to detect at echocardiography (3) but are readily demonstrated at CT or MR imaging, both of which provide a wider field of view (Fig 3). CT attenuation measurements also enable the initial characterization of pericardial fluid. A fluid collection with attenuation close to that of water is likely to be a simple effusion (Fig 4). Attenuation greater than that of water suggests malignancy, hemopericardium, purulent exudate, or effusion associated with hypothyroidism (Fig 5) (19). Pericardial effusions with low attenuation also have been reported in cases of chylopericardium (19). The appearance of pericardial fluid is different on SE and GRE cine MR images. Nonhemorrhagic fluid has low signal intensity on T1-weighted SE images and high intensity on GRE cine images (Fig 6) (20). Conversely, hemorrhagic effusion is characterized by high signal intensity on T1-weighted SE images and low intensity on GRE cine images (Fig 7) (20). When an effusion is secondary to malignancy, an irregularly thickened pericardium or pericardial nodularity may be depicted on MR images. Because most or all of the chest is evaluated during CT or MR imaging of the pericardium, associated abnormalities in the mediastinum and lungs also may be detected during the examination.
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Figure 3. Loculated pericardial effusion in a 65-year-old man with recent thoracotomy. Axial contrast-enhanced CT scan shows a loculated pericardial effusion that compresses the right atrium. The parietal pericardium (arrow) clearly separates the loculated pericardial effusion (*) from the pleural effusion (P).
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Figure 5. Pericardial effusion in a 46-year-old man with shortness of breath. Axial contrast-enhanced CT scan shows a moderate-sized enhancing (35 HU) effusion (*), which was identified at subsequent pericardiocentesis as serosanguineous fluid.
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Figure 6. Pericardial effusion in a 34-year-old woman with nephrotic syndrome. Cine GRE image shows a high-signal-intensity pericardial effusion (*) consistent with nonhemorrhagic fluid.
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Figure 7. Pericardial effusion in a 68-year-old woman with a recent history of myocardial infarction. Axial ECG-gated T1-weighted SE image shows an effusion with high signal intensity (*) suggestive of hemorrhage.
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Constrictive Pericarditis
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Patients with constrictive pericarditis frequently present with symptoms of heart failure, such as dyspnea, orthopnea, and fatigability, and occasionally may present with liver enlargement and ascites. The causes of constrictive pericarditis have changed over time; at present, the most frequent causes are cardiac surgery and radiation therapy (21). Other causes include infection (viral or tuberculous), connective-tissue disease, uremia, neoplasm, or idiopathic condition (Table 1) (22).
Clinically, it is difficult to differentiate between constrictive pericarditis and restrictive cardiomyopathy. These two entities are characterized by similar clinical manifestations and similar findings at cardiac catheterization and echocardiography. In both conditions, ventricular filling is restricted, leading to an increase in diastolic pressure in all four cardiac chambers and to equalization of atrial and ventricular pressure. It is important, however, to distinguish between constrictive pericarditis and restrictive cardiomyopathy, because patients with constrictive pericarditis might benefit from pericardial stripping, whereas those with restrictive disease would not.
Although transthoracic echocardiography is routinely performed for the evaluation of myocardial function in patients with symptoms of constrictive or restrictive physiologic change, it is not highly accurate in the depiction of pericardial thickening (4). Transesophageal imaging allows better visualization of the pericardium, and respiration-correlated Doppler techniques are particularly useful in the diagnosis of constrictive pericarditis (23). However, the transesophageal approach is limited by a narrow field of view and is relatively invasive.
The diagnosis of constrictive pericarditis is greatly aided by the excellent depiction of the pericardium at CT and MR imaging. Normal pericardial thickness is less than 2 mm (Fig 1) (8,9). Pericardial thickness of 4 mm or more indicates abnormal thickening and, when it is accompanied by clinical findings of heart failure, is highly suggestive of constrictive pericarditis (Figs 8–11). MR imaging has a reported accuracy of 93% for differentiation between constrictive pericarditis and restrictive cardiomyopathy on the basis of depiction of thickened pericardium (
4 mm) (24). Pericardial thickening may be limited to the right side of the heart (Fig 11) or to an even smaller area, such as the right atrioventricular groove (25). An additional advantage of CT is its high sensitivity in depicting pericardial calcification, which is also associated with constrictive pericarditis (Fig 12). It is important to remember, however, that neither pericardial thickening nor calcification is diagnostic of constrictive pericarditis unless the patient also has symptoms of physiologic constriction or restriction.
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Figure 8. Constrictive pericarditis in a 55-year-old man who presented with symptoms of heart failure after mediastinal irradiation for Hodgkin lymphoma. Axial contrast-enhanced CT scan shows pericardial thickening (arrows).
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Figure 9. Constrictive pericarditis in a 51-year-old man who presented with symptoms of constriction. Coronal ECG-gated T1-weighted SE image shows abnormally thickened pericardium (arrows) outlined by epicardial and anterior mediastinal fat.
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Figure 10a. Constrictive pericarditis in a 65-year-old man who had had symptoms of right heart failure for 3 months. (a) Axial ECG-gated T1-weighted SE image shows pericardial thickening (arrows), which is most visible near the right ventricle. The right ventricle has a narrow tubular shape secondary to pericardial constriction. (b) Axial T1-weighted SE image obtained at a level slightly caudad to that in a shows dilatation of the inferior vena cava (IVC) and ascites (*).
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Figure 10b. Constrictive pericarditis in a 65-year-old man who had had symptoms of right heart failure for 3 months. (a) Axial ECG-gated T1-weighted SE image shows pericardial thickening (arrows), which is most visible near the right ventricle. The right ventricle has a narrow tubular shape secondary to pericardial constriction. (b) Axial T1-weighted SE image obtained at a level slightly caudad to that in a shows dilatation of the inferior vena cava (IVC) and ascites (*).
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Figure 11. Constrictive pericarditis in a 37-year-old man who presented with shortness of breath 20 years after undergoing irradiation for lymphoma. Axial ECG-gated T1-weighted SE image shows focal pericardial thickening over the right ventricle and right atrium (arrows). The right ventricle (RV) has a tubular shape caused by constriction.
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At both CT and MR imaging, the central cardiovascular structures may show a characteristic morphology in constrictive pericarditis. The right ventricle tends to have a reduced volume and a narrow tubular configuration (Figs 10a, 11). In some patients, a sigmoid-shaped ventricular septum or prominent leftward convexity in the septum can be observed (25). Systemic venous dilatation (particularly in the inferior vena cava), hepatomegaly, and ascites also are frequently seen (Fig 10b).
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Pericarditis without Constriction
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Pericardial thickening may occur in the absence of constrictive pericarditis. Pericardial thickening may result from inflammation caused by a variety of conditions, including acute pericarditis, uremia, rheumatic heart disease, rheumatoid arthritis, sarcoidosis, and mediastinal irradiation.
At contrast-enhanced CT, enhancement of the thickened pericardium indicates inflammation (Fig 13). A limitation of CT imaging of the pericardium is the occasional difficulty in differentiating a small effusion from pericardial thickening. Echocardiography may depict the effusion more clearly in such cases. The signal intensity of the thickened pericardium on ECG-gated MR images is variable. Normal pericardium is composed primarily of fibrous tissue and has a low signal intensity on both T1- and T2-weighted MR images. The purely fibrous or calcified pericardium in chronic pericardial disease also has low signal intensity. However, in subacute forms of pericarditis, the thickened pericardium has moderate to high signal intensity on SE images. Enhancement of the thickened pericardium after the administration of gadolinium-based contrast material alsosuggests inflammation (Figs 14–16). The effusive-constrictive form of pericarditis involves both pericardial thickening and pericardial effusion (Figs 14, 15).
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Figure 13. Infectious pericarditis in a 59-year-old woman with shortness of breath and chest pain. Axial contrast-enhanced CT scan shows enhancement of the pericardium (arrows), indicative of inflammation. Note the associated small pericardial effusion and large bilateral pleural effusions (P). Findings at subsequent pericardiocentesis confirmed exudative effusion.
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Figure 14a. Effusive constrictive pericarditis secondary to viral infection in a 65-year-old man with symptoms of heart failure. (a) Axial ECG-gated T1-weighted SE image shows a crescent-shaped area of intermediate signal intensity (arrows) surrounding the ventricles, which indicates either pericardial thickening or pericardial effusion. (b) Axial gadolinium-enhanced fat-saturated T1-weighted SE image shows marked thickening and enhancement in the pericardium (arrows), findings consistent with inflammation. A moderate-sized pericardial effusion is also depicted.
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Figure 14b. Effusive constrictive pericarditis secondary to viral infection in a 65-year-old man with symptoms of heart failure. (a) Axial ECG-gated T1-weighted SE image shows a crescent-shaped area of intermediate signal intensity (arrows) surrounding the ventricles, which indicates either pericardial thickening or pericardial effusion. (b) Axial gadolinium-enhanced fat-saturated T1-weighted SE image shows marked thickening and enhancement in the pericardium (arrows), findings consistent with inflammation. A moderate-sized pericardial effusion is also depicted.
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Figure 15. Effusive constrictive pericarditis secondary to Mycobacterium tuberculosis in a 44-year-old man with symptoms of heart failure. Axial gadolinium-enhanced ECG-gated fat-saturated T1-weighted SE image shows an enhancing thickened pericardium (arrows) and a moderate-sized pericardial effusion (*).
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Figure 16a. Inflammatory constrictive pericarditis in an 8-year-old boy with progressive shortness of breath after undergoing surgical repair of an atrial septal defect. Axial ECG-gated T1-weighted SE image (a) and axial gadolinium-enhanced fat-saturated T1-weighted SE image (b) show an abnormally thickened pericardium (arrows in a) that enhances after gadolinium administration (arrows in b).
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Figure 16b. Inflammatory constrictive pericarditis in an 8-year-old boy with progressive shortness of breath after undergoing surgical repair of an atrial septal defect. Axial ECG-gated T1-weighted SE image (a) and axial gadolinium-enhanced fat-saturated T1-weighted SE image (b) show an abnormally thickened pericardium (arrows in a) that enhances after gadolinium administration (arrows in b).
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Pericardial Masses
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The differential diagnosis of pericardial masses includes pericardial cyst, hematoma, and neoplasm (Table 2). Although pericardial masses are often detected initially with echocardiography, CT and MR imaging are useful for the further evaluation of these masses. CT attenuation or MR signal intensity characteristics, degree of contrast enhancement, and presence or absence of blood flow on cine MR images can help differentiate among pericardial masses. CT and MR imaging also can be used to accurately define the site and extent of masses.
Cysts
Congenital pericardial cysts are formed when a portion of the pericardium is pinched off during early development. Pericardial cysts usually have thin smooth walls without internal septa. At CT, they have the same attenuation as water and do not enhance after contrast material administration (Fig 17). At MR imaging, they typically have low or intermediate signal intensity on T1-weighted images and homogeneous high intensity on T2-weighted images. They do not enhance with the administration of gadolinium chelates (Fig 18) (7). Occasionally, a cyst may contain highly proteinaceous fluid, which may have a high signal intensity on T1-weighted images. Pericardial cysts may occur anywhere in the mediastinum, although they usually are found in the right cardiophrenic angle. A pericardial cyst in an unusual location may be indistinguishable from a bronchogenic cyst or thymic cyst.
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Figure 17a. Pericardial cyst in an asymptomatic 68-year-old man. (a) Axial unenhanced CT scan shows a homogeneous mass (arrows) that has the same attenuation as water, adjacent to the pulmonary artery. (b) Axial contrast-enhanced CT scan shows no enhancement of this mass, a characteristic consistent with pericardial cyst.
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Figure 17b. Pericardial cyst in an asymptomatic 68-year-old man. (a) Axial unenhanced CT scan shows a homogeneous mass (arrows) that has the same attenuation as water, adjacent to the pulmonary artery. (b) Axial contrast-enhanced CT scan shows no enhancement of this mass, a characteristic consistent with pericardial cyst.
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Figure 18a. Pericardial cyst in an asymptomatic 56-year-old man. (a) Axial ECG-gated T1-weighted SE image shows a mass (*) with intermediate signal intensity, adjacent to the main pulmonary artery. (b) Axial gadolinium-enhanced T1-weighted image obtained at the same level as a shows no enhancement of the mass (*) after administration of gadolinium. (c) Axial T2-weighted fast SE image shows a mass (*) with homogeneous high signal intensity. PA = pulmonary artery.
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Figure 18b. Pericardial cyst in an asymptomatic 56-year-old man. (a) Axial ECG-gated T1-weighted SE image shows a mass (*) with intermediate signal intensity, adjacent to the main pulmonary artery. (b) Axial gadolinium-enhanced T1-weighted image obtained at the same level as a shows no enhancement of the mass (*) after administration of gadolinium. (c) Axial T2-weighted fast SE image shows a mass (*) with homogeneous high signal intensity. PA = pulmonary artery.
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Figure 18c. Pericardial cyst in an asymptomatic 56-year-old man. (a) Axial ECG-gated T1-weighted SE image shows a mass (*) with intermediate signal intensity, adjacent to the main pulmonary artery. (b) Axial gadolinium-enhanced T1-weighted image obtained at the same level as a shows no enhancement of the mass (*) after administration of gadolinium. (c) Axial T2-weighted fast SE image shows a mass (*) with homogeneous high signal intensity. PA = pulmonary artery.
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Hematomas
MR imaging is particularly useful for the diagnosis of pericardial hematomas, which have a characteristic signal intensity on T1-weighted and T2-weighted MR images: Acute hematomas demonstrate homogeneous high signal intensity (26,27), whereas subacute hematomas that are 1–4 weeks old typically show heterogeneous signal intensity, with areas of high signal intensity on both T1-weighted and T2-weighted images (Fig 19a) (26,28). On T1-weighted and gradient-echo images, chronic organized hematomas may show a dark peripheral rim and low-signal-intensity internal foci that may represent calcification, fibrosis, or hemosiderin deposition (Fig 20) (29,30). High-signal-intensity areas on T1-weighted or T2-weighted images often correspond to hemorrhagic fluid (31). Coronary or ventricular pseudoaneurysms or neoplasms may resemble hematomas on MR images. However, the administration of gadolinium chelates allows the differentiation of these entities, because hematomas do not enhance (Fig 19b). Additionally, velocity-encoded cine MR imaging may be used to detect internal flow in pseudoaneurysms (32) and thus to differentiate pseudoaneurysms from hematomas (Fig 19c, 19d).
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Figure 19a. Organized pericardial hematoma in a 70-year-old woman with a history of coronary artery disease and angioplasty of the right coronary artery. (a) Axial ECG-gated T1-weighted SE image shows a mass (M) with heterogeneous signal intensity in the right atrioventricular groove. (b) Axial gadolinium-enhanced T1-weighted image shows no enhancement of the mass (M). (c, d) Magnitude (c) and phase velocity-encoded (d) cine images show no blood flow in the mass (M), a finding indicative of hematoma rather than pseudoaneurysm.
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Figure 19b. Organized pericardial hematoma in a 70-year-old woman with a history of coronary artery disease and angioplasty of the right coronary artery. (a) Axial ECG-gated T1-weighted SE image shows a mass (M) with heterogeneous signal intensity in the right atrioventricular groove. (b) Axial gadolinium-enhanced T1-weighted image shows no enhancement of the mass (M). (c, d) Magnitude (c) and phase velocity-encoded (d) cine images show no blood flow in the mass (M), a finding indicative of hematoma rather than pseudoaneurysm.
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Figure 19c. Organized pericardial hematoma in a 70-year-old woman with a history of coronary artery disease and angioplasty of the right coronary artery. (a) Axial ECG-gated T1-weighted SE image shows a mass (M) with heterogeneous signal intensity in the right atrioventricular groove. (b) Axial gadolinium-enhanced T1-weighted image shows no enhancement of the mass (M). (c, d) Magnitude (c) and phase velocity-encoded (d) cine images show no blood flow in the mass (M), a finding indicative of hematoma rather than pseudoaneurysm.
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Figure 19d. Organized pericardial hematoma in a 70-year-old woman with a history of coronary artery disease and angioplasty of the right coronary artery. (a) Axial ECG-gated T1-weighted SE image shows a mass (M) with heterogeneous signal intensity in the right atrioventricular groove. (b) Axial gadolinium-enhanced T1-weighted image shows no enhancement of the mass (M). (c, d) Magnitude (c) and phase velocity-encoded (d) cine images show no blood flow in the mass (M), a finding indicative of hematoma rather than pseudoaneurysm.
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Figure 20a. Chronic organized pericardial hematoma in a 39-year-old man who presented with syncope and chest discomfort and had a history of blunt chest trauma 8 years prior. (a) Axial ECG-gated T1-weighted SE image shows a well-circumscribed mass (M) with intermediate signal intensity in the left atrioventricular groove; the mass compresses the left atrium and ventricle. (b) Axial cine GRE image shows a mass (M) with low-signal-intensity foci and a low-signal-intensity rim (arrows), which are indicative of central and peripheral calcifications. These findings were confirmed at subsequent surgery.
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Figure 20b. Chronic organized pericardial hematoma in a 39-year-old man who presented with syncope and chest discomfort and had a history of blunt chest trauma 8 years prior. (a) Axial ECG-gated T1-weighted SE image shows a well-circumscribed mass (M) with intermediate signal intensity in the left atrioventricular groove; the mass compresses the left atrium and ventricle. (b) Axial cine GRE image shows a mass (M) with low-signal-intensity foci and a low-signal-intensity rim (arrows), which are indicative of central and peripheral calcifications. These findings were confirmed at subsequent surgery.
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Neoplasms
Pericardial metastases are much more common than primary pericardial tumors and are discovered at autopsy in 10%–12% of all patients with malignancy (33,34). Tumors may seed the pericardium via the lymph system or the blood stream or may invade directly from the lung or mediastinum (35). Breast and lung cancers are the most common sources of metastases in the pericardium, followed by lymphomas and melanomas (34). Metastatic involvement of the pericardium may be suggested by CT findings of effusion and irregularly thickened pericardium or pericardial mass (Fig 21). On MR images, an intact pericardial line may be observed if an adjacent tumor extends to the pericardium but not through it. Tumors that have invaded the pericardium may be recognized by focal obliteration of the pericardial line and the presence of pericardial effusion. Hemorrhagic pericardial effusions secondary to metastases usually have high signal intensity on SE images (20). Most neoplasms have low signal intensity on T1-weighted images and high signal intensity on T2-weighted images (36). Metastatic melanoma is an exception; it may have high signal intensity on T1-weighted images because of the paramagnetic metals bound by melanin (37,38). Sites of malignant disease usually enhance significantly after the administration of contrast material (Fig 21) (25,39).
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Figure 21. Metastatic pericardial lymphoma in a 36-year-old man. Axial contrast-enhanced CT scan shows a large heterogeneous anterior mediastinal mass (M) with central necrosis, which has invaded the pericardium (arrowheads). A moderate-sized pericardial effusion (*) and associated enhancement of the pericardium (arrow) also are evident.
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Primary neoplasms of the pericardium are rare. Benign pericardial tumors include lipoma, teratoma, fibroma, and hemangioma; malignant tumors include mesothelioma, lymphoma, sarcoma, and liposarcoma. Lipoma typically has low attenuation on CT images and high signal intensity on T1-weighted SE images. Depiction of calcium or fat in a pericardial mass at CT suggests teratoma. Fibroma characteristically has low signal intensity on T2-weighted images and often shows either no enhancement or heterogeneous enhancement because of poor vascularization (39,40). Primary malignant mesothelioma of the pericardium may manifest as pericardial effusion (Fig 22), occasionally accompanied by pericardial nodules or plaques. Malignant pleural mesothelioma also may invade the pericardium directly. Lymphoma (Fig 23), sarcoma (Fig 24), and liposarcoma typically appear as large heterogeneous masses frequently associated with serosanguineous pericardial effusion. Biopsy and histopathologic analysis are necessary to achieve a definitive diagnosis of most pericardial tumors.
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Figure 22. Biopsy-proved primary pericardial mesothelioma in a 60-year-old man with fatigue and dyspnea on exertion. Axial contrast-enhanced CT scan shows a large pericardial effusion (*) and no pericardial nodules. Pericardial nodules occur in this disease but are rare.
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Figure 23. Biopsy-proved primary pericardial lymphoma in a 45-year-old man with shortness of breath. Axial contrast-enhanced CT scan shows an irregular enhanced soft-tissue mass (*) that has infiltrated the entire pericardium.
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Figure 24. Biopsy-proved primary pericardial sarcoma in an asymptomatic 57-year-old man. Axial contrast-enhanced CT scan shows an enhanced soft-tissue mass (*) in the pericardium adjacent to the left atrial appendage.
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Congenital Absence of the Pericardium
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Congenital absence of the pericardium is rare. Most pericardial defects are partial and occur on the left side. Infrequently, defects also occur on the right side or at the diaphragmatic surface. Normally, the aortopulmonary window is covered by pericardium and contains some fat. Left-sided absence of the pericardium allows interposition of lung tissue between the aorta and the main segment of the pulmonary artery, and, occasionally, bulging of the left atrial appendage through the defect. As a result of these abnormalities, the heart usually rotates toward the left. Although radiographs may show evidence of this condition, a definitive diagnosis can be obtained with either CR or MR imaging (Fig 25).
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Figure 25a. Congenital absence of the pericardium. Axial contrast-enhanced CT scan (a) and ECG-gated T1-weighted SE image (b) show interposition of lung tissue between the aorta and the main segment of the pulmonary artery (arrow), indicating the absence of the pericardium in this area. Note the rotation of the heart toward the left.
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Figure 25b. Congenital absence of the pericardium. Axial contrast-enhanced CT scan (a) and ECG-gated T1-weighted SE image (b) show interposition of lung tissue between the aorta and the main segment of the pulmonary artery (arrow), indicating the absence of the pericardium in this area. Note the rotation of the heart toward the left.
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Patients with pericardial defects also may have one or more associated congenital abnormalities, including atrial septal defect, patent ductus arteriosus, mitral valve stenosis, or tetralogy of Fallot (41), which also are detectable on CT or MR images. Patients who have a pericardial defect without associated congenital abnormalities are often asymptomatic. Complications of congenital pericardial defect may include herniation and entrapment of a cardiac chamber, especially the left atrial appendage. Surgical closure or enlargement of the defect is sometimes necessary to alleviate herniation.
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Conclusions
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Infection, neoplasm, injury, and congenital disease all may affect the pericardium. Although echocardiography is the primary imaging modality used to examine the pericardium, CT and MR imaging provide various advantages, especially in cases of loculated or hemorrhagic effusion, constrictive pericarditis, and pericardial masses. CT and MR imaging should be used when findings at echocardiography are difficult to interpret or conflict with clinical findings.
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Footnotes
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Abbreviations: ECG = electrocardiographic,
GRE = gradient-recalled echo,
SE = spin-echo
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References
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Abstract
Introduction
