Coronary Artery Evaluation
Goals in the assessment of coronary artery disease include identification of coronary plaques and flow-limiting coronary stenoses, measurement of atherosclerotic burden, and characterization of plaque components.18 Identification and quantification of calcified plaques can be performed using a noncontrast CT study. Further information on atherosclerotic burden, presence of noncalcified or mixed plaques, and assessment for stenoses requires a contrast CT study.
Noncontrast CT for Calcium Scoring
Atherosclerotic coronary calcifications are often found in patients with long-standing coronary atherosclerosis. Elevated levels of coronary calcification have been shown to correspond to increased risk of myocardial events.19-22 Current clinical indications for quantification of coronary calcium are in patients with atypical chest pain, as well as asymptomatic patients with traditional cardiovascular risk factors.23 Noncontrast CT is currently the only method available to accurately quantify the coronary calcium plaque burden. Coronary artery calcium is assessed through the measurement of the number of pixels in the CT image with a density ≥130 Hounsfield units (HU) to calculate a total calcium score,24 a calcium volumetric score,25 or an absolute calcium mass26 (Fig. 5–8). Each method has shown similar reproducibility,27-29 and most software processing programs can easily provide all three scores simultaneously. A high coronary calcium score is a sensitive but nonspecific marker for obstructive coronary artery disease (CAD), and changes in the calcium score have not been shown to correspond to changes in cardiovascular event risk.23
Coronary calcium scoring. CX, circumflex; LAD, left anterior descending; LM, left main; RCA, right coronary artery.
Noncalcified atherosclerotic plaques in the coronary arteries can be visualized using contrast-enhanced CT. The high spatial resolution and soft tissue delineation can provide information about the content of atherosclerotic plaques and coronary artery wall,30 including distinction between low-density lipid-rich (47 ± 9 HU) versus higher density fibrous (104 ± 28 HU) plaques.31,32 Several studies have demonstrated the high sensitivity (72%-99%) and specificity (86%-97%) and particularly the high negative predictive value (97%-100%) of MDCT when compared against the gold standards of x-ray coronary angiography and intravascular ultrasound for the detection of significant CAD.33-39 More importantly, with increasing number of detectors and faster gantry speeds leading to an improvement in image resolution, there has been a significant increase in the number of evaluable segments compared with early-generation scanners. The presence of coarse calcifications with related blooming and streak artifact, however, still remains problematic in regard to accurate interpretation of degree of luminal narrowing.
Anomalies of the coronary arteries affect approximately 1% of the population, with 87% of these individuals having anomalies of the origin and distribution and 13% having coronary artery fistulae.40,41 The true incidence of ectopic origin of the coronary arteries from the aorta in the population is unknown but estimated to be between 0.17% and 0.6%. Cardiac catheteri-zation has traditionally been the preferred imaging modality for characterization of coronary artery anomalies. However, given the complex 3D nature of these anomalies, not infrequently, conventional angiography incompletely delineates the anatomic origin and course of the coronary artery. CTA of the coronary arteries has therefore become one of the accepted standards for complete evaluation of coronary artery anomalies. With the high spatial resolution, volumetric acquisition, and orientation in any plane, CT can accurately depict the origin and course of coronary artery anomalies with high sensitivity, although specificity is reduced in patients with high heart rates due to the limited temporal resolution even with cardiac gating.42,43
Assessment of Stent Patency
With the growth of nonsurgical revascularization techniques, there has been an enormous increase in the number of patients with CAD who receive coronary artery stents.44,45 Hence, early identification of in-stent restenosis is important in the management of these patients. MDCT has shown variable success for evaluation of in-stent restenosis with steady improvements noted when using newer 64-slice systems offering improvement in spatial resolution, particularly when using dedicated reconstruction kernels.45-53 However, there is still high variability of stent lumen visibility depending on the stent type, size, orientation, and surrounding tissue (Fig. 5–9). Sharp reconstruction kernels, in addition to the routine medium kernels, may provide improvement in visible lumen diameter as well as more realistic intraluminal attenuation values.44,45
Oblique multiplanar reconstructed computed tomography images demonstrating patent (top row) and occluded stents (bottom row).
Assessment of Bypass Grafts
Surgical revascularization of CAD is accomplished by coronary artery bypass grafting in which a graft (arterial or venous) is used to bypass an occluded or stenosed coronary artery. Compared with the native coronary arteries, reversed saphenous vein and internal mammary artery grafts are easier to visualize due to the reduced overall motion, larger lumen, and less convoluted course. Familiarity with the common types of grafts used and placement can aid in both planning and interpretation of images (Fig. 5–10). Venous conduits are generally wider and longer than their arterial counterparts but have reduced long-term patency.
Volume-rendered computed tomography images demonstrating different bypass graft types including free saphenous vein grafts (black arrowheads), in situ internal mammary artery grafts (white arrowheads), sequential bypass grafts (white arrows), and "Y" or "T" grafts (black arrows). OG, occluded graft.
With the MDCT technique, special considerations must be taken into account during data acquisition. Because most patients have an in situ mammary artery graft, image acquisition must cover the entire thorax in order to visualize the proximal anastomosis and origin of the internal mammary arteries. Given the larger volume of coverage, adjustments in contrast dose and scan delay timing after contrast administration should be made to ensure adequate contrast enhancement of the bypass grafts and native coronary artery vessels during image acquisition. MDCT has been shown to have high sensitivity (97%-100%) and specificity (98%) for diagnosing graft occlusion, although somewhat lower sensitivity (75%-82%) and specificity (88%-92%) for detecting significant stenoses.54,55
Pulmonary Vein Evaluation
There has been an increase in the number of interventional procedures performed for the treatment of atrial arrhythmias. In particular, atrial fibrillation, which affects approximately 2 million people in the United States,56 can now be treated using an ablation technique, often pulmonary vein isolation. Imaging evaluation of the left atrial anatomy and pulmonary venous anatomy can aid the eletrophysiologist in preprocedural planning and can be used to asses for postprocedural complications. Three-dimensional visualization of the left atrium and pulmonary venous anatomy is often used to guide the electrophysiologist in navigating the left atrial cavity during catheter ablation.
The location, size, and number of pulmonary veins need to be defined. Ostial branches, which are venous branches noted within 5 mm of the atriopulmonary venous junction, are also important to note. Commonly, there are four pulmonary veins with separate ostia into the left atrium. Knowledge of aberrant pulmonary veins (Fig. 5–11) such as accessory or conjoined veins and incidental left atrial diverticula can help guide procedures to ensure isolation of the electrical potentials arising from all the pulmonary veins and avoid potential complications from attempts to enter atrial diverticula. Diagnosis of the presence of left atrial thrombus, especially prevalent in the left atrial appendage, is important to prevent iatrogenic systemic embolism (Fig. 5–12).
Volume-rendered computed tomography (left) and corresponding shaded surface reconstruction (right) of the interior of the left atrium demonstrating pulmonary venous anatomy with additional draining vein on the right.
Early (left) and delayed (right) first-pass perfusion computed tomography image in two-chamber view of the heart demonstrating persistent filling defect in the left atrial appendage representing thrombus (arrow).
Postprocedural complications of radiofrequency ablation include endocardial scarring (Fig. 5–13), pulmonary vein dissection, and perforation.57 Small pleural or pericardial effusions, small atrial septal defects, and pulmonary venous stenosis are also potential complications. Serious complications include stroke, hemopericardium, hemothorax, pulmonary vein thrombosis, and hemodynamically significant pulmonary vein stenosis, which can result in pulmonary veno-occlusive disease including focal pulmonary edema.58 Pulmonary vein stenosis may develop up to 8 months after the procedure. Current ablation techniques, however, have greatly diminished the complication rate of pulmonary venous stenosis.
Multiplanar reformatted computed tomography images demonstrating significant stenosis of the left superior (A) and left inferior (B) pulmonary vein ostia. Three-dimensional shaded surface endoluminal view (C) and volume-rendered (D) images demonstrate the anatomy. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein.
Imaging of the left atrial and pulmonary venous anatomy can be performed with CT or magnetic resonance imaging (MRI). CTA imaging can be performed as a gated or nongated study and should encompass the area from the aortic arch through the apex of the heart during a single breath-hold.59 Postprocessing of the image data sets, including 2D multiplanar reconstructions of the pulmonary venous ostia and atrial appendage, and 3D volume-rendered and shaded surface displays demonstrate the complex anatomy. Depending on the software vendor, volumetric CT data sets acquired through the left atrium can be synchronized and fused with electrical mapping systems in the electrophysiology laboratory (Fig. 5–14).
Synchronization of electrical voltage 3D map (left) and corresponding 3D volume-rendered computed tomography image (right) of the left atrium used for guiding electrophysiology intervention. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; RSPV, right superior pulmonary vein.
Over the past five decades, the number of adults with congenital heart disease has grown due to the advances in cardiac surgery, intensive care, and noninvasive diagnosis.60 Approximately 85% of infants with cardiovascular anomalies can be expected to survive into adulthood, and with further advancements in surgical techniques, this number may continue to grow.61 Although surgical correction of an anomaly may reestablish a relatively normal pattern of blood flow, these adult survivors still remain at significant risk for developing complications from their operative procedures or from lingering effects of the original anomaly. Hence, these patients need to be followed closely regardless of their stage of treatment. As such, comprehensive imaging evaluation of the cardiovascular anatomy, flow, and function is important in the management of these patients. Cardiac MDCT with its fast acquisition times and capacity to obtain volumetric 3D information with high spatial resolution has often been used in the anatomic evaluation of congenital heart disease (Fig. 5–15). Advantages of CT compared with other imaging modalities such as cardiac MRI include short examination, fewer requirements for sedation, simultaneous evaluation of airways and lung parenchyma, and high spatial resolution. Disadvantages include radiation exposure, use of iodinated contrast, and lack of hemodynamic information.
Multiplanar reformatted (top row) and three-dimensional volume-rendered (bottom row) computed tomography images demonstrating partial anomalous pulmonary venous return of the right-sided pulmonary veins (RPV) into the subdiaphragmatic inferior vena cava (IVC) with some narrowing noted at the ostium (red arrow).
CT imaging protocol is dependent on the structure of interest and information needed. For patients with abnormalities in the vascular system, image acquisition is usually started a few centimeters above the aortic arch and continued to the diaphragm. Because congenital heart disease often involves abnormalities in both the right and left heart chambers, the timing of data acquisition is set such that there is optimal contrast enhancement seen in both sides of the heart. In cases with intracardiac shunting, imaging can be performed early (within 5 seconds of contrast administration) and late (approximately 30 seconds after contrast administration) in order to determine the degree and direction of shunting.62 Images can be evaluated using multiplanar reconstructions, maximum intensity projections and 3D volume rendered image sets. Data can also be reconstructed in multiple phases through the cardiac cycle for calculation of cardiac volumes and function.
Diseases of the pericardium encompass a spectrum of disorders including congenital malformations and infection-related, infarction-related, metabolic, autoimmune, traumatic, neoplastic, and idiopathic disorders. Depending on the disease process, clinical manifestations of pericardial involvement can vary. Suspected pericardial disease is usually initially evaluated with echocardiography. However, CT imaging can also provide additional valuable information.
CT imaging has been widely accepted for the evaluation of structural changes in the pericardium. The best quality images in the evaluation of pericardial disease are obtained with the use of cardiac gating and fast imaging to minimize motion blurring, although more prominent pericardial disease findings may be evident even on conventional studies performed for other indications. On CT, the pericardium is usually well delineated from the adjacent low-attenuation fat. Anatomic features of pericardial disease such as pericardial thickening, pericardial calcification, and pericardial effusion or masses are easily detected and evaluated with CT. Limited tissue characterization of pericardial fluid/masses can make it difficult to differentiate thickened pericardium from an exudative pericardial effusion with high protein content. Functional and hemodynamic information is also limited with CT. However, CT is the most sensitive technique for detection of pericardial calcification.
The CT appearance of pericardial effusion is often not very specific for a particular etiology, and further evaluation is usually necessary to help narrow the range of differential possibilities. CT attenuation measurements can provide initial characterization of pericardial fluid. On CT, simple effusions have attenuation similar to that of water. In contrast, more proteinaceous fluid (exudates or inspissated fluid collections) will have attenuation greater than water on CT.63 CT characteristics of malignant effusions may be similar to hemorrhagic effusions, depending on blood content, and are often associated with an irregularly thickened pericardium or pericardial nodularity. In addition, because of the wide field of view, associated abnormalities of the mediastinum and lungs may also be detected during the examination.64
Acute pericarditis may or may not be accompanied by pericardial effusion and some degree of myocarditis depending on etiology. Clinical symptoms and serologic markers of inflammation can often support the diagnosis. CT imaging can be used to aid in the diagnosis, especially when other tests prove inconclusive. Structural changes of the pericardium such as thickening, inflammation, pericardial effusion, and associated myocarditis or other concomitant heart disease and mediastinal pathology can be demonstrated.
Chronic inflammation of the pericardium can lead to constrictive pericarditis, which is characterized by impaired ventricular filling. The process may extend to involve the underlying myocardium, resulting in reduced ventricular function. The etiology of constrictive pericardial disease has often been attributed to antecedent acute pericarditis due to infectious, inflammatory, or idiopathic causes. However, other etiologies such as neoplastic diseases, postradiation therapy, postcardiac surgery, and remote nonpenetrating or penetrating cardiac trauma have been frequently seen. Accurate diagnosis and differentiation from restrictive cardiomyopathy are important because curative treatment for constrictive pericarditis is possible with surgical pericardiectomy. Initial diagnostic workup usually includes 2D, Doppler, and tissue Doppler echocardiography with analysis of respiratory changes associated or not with changes of preload. However, equivocal findings may be present in up to one-third of patients with possible pericardial constriction, and further testing is usually required.
Direct visualization of the pericardium can be performed with CT for measurement of pericardial thickness. However, the finding of a thickened pericardium is not necessarily confirmatory of constrictive pericarditis. In addition, up to 20% of patients with constrictive pericarditis may present with normal-thickness pericardium on current imaging methods.65 CT can also demonstrate characteristic anatomic features for constrictive pericarditis including a conical or tubular diastolic ventricular shape, an associated pericardial effusion, pericardial calcification (Fig. 5–16), and secondary sequelae including dilated atria, hepatic veins, and pulmonary veins, which can further support the diagnosis of constrictive pericarditis.
Multiplanar reformatted computed tomography image demonstrating pericardial calcifications (arrows) that can be seen in constrictive pericarditis.
The differential diagnosis of pericardial masses includes pericardial cyst, hematoma, neoplasm, loculated effusions, or pseudoaneurysms. Although often detected initially with echocardiography, evaluation with CT can be helpful in diagnosis and treatment. CT characteristics such as tissue attenuation, degree of contrast enhancement, and presence or absence of blood flow into the mass can help differentiate among pericardial masses. In addition, the size, anatomic extent, associated lesions, vascularity, and effects on cardiac function of the masses can be clarified. Furthermore, CT can guide other diagnostic testing, such as biopsy, and facilitate treatment and follow-up.
Congenital Pericardial Lesions
Congenital defects of the pericardium comprise partial left, right, or diaphragmatic or total absence of the pericardium. Most patients are asymptomatic, although approximately 30% may have additional congenital abnormalities. Complete absence of the pericardium poses a risk of homolateral cardiac displacement and amplified heart mobility and an increased risk of traumatic aortic type A dissection. Partial left-sided defects can be complicated by cardiac strangulation caused by herniation of the left atrial appendage, atrium, or left ventricle through the defect. Although the diagnosis can be suggested by chest x-ray and echocardiography, definitive diagnosis and complete evaluation of the pericardium can be performed with CT.
Cardiac masses may be divided into benign or malignant lesions. Benign cardiac tumors include cardiac neoplasms, pseudotumors such as thrombi, and normal structures that resemble masses. Malignant cardiac tumors include both primary and secondary malignancies that can affect the heart. Echocardiography is often the initial diagnostic test to evaluate cardiac masses but often provides limited information on tissue characterization and extent of extracardiac involvement or presence of metastatic disease. Therefore, cross-sectional imaging with CT can provide additional information including the precise location of cardiac tumors (eg, paracardiac, mural, or intracavitary), the extent of disease, the presence of associated effusions, and the presence of metastases66 (Fig. 5–17). Additionally, CT imaging findings including tissue characterization may suggest the tumor type, which can be important in treatment planning (Table 5–2).
Table 5–2. CT Characteristic Features of Cardiac Masses ||Download (.pdf)
Table 5–2. CT Characteristic Features of Cardiac Masses
|Mass||CT Characteristics||Distribution and Features|
|Thrombus||Hypodense||Atrial appendage, left ventricular aneurysms|
|Myxoma||Heterogeneous hypodense||Attachment to interatrial septum; commonly in left atrium|
|Papillary fibroelastoma||Hypodense||Solitary, mobile, pedunculated|
|Lipoma||Hypodense||Encapsulated mass with smooth contour|
|Fibroma||Hypodense with areas of calcification||Large, solitary, intramyocardial|
|Rhabdomyoma||Hypodense||Multicentric masses, intramural or intracavitary|
|Teratoma||Heterogeneous often with calcification in the form of teeth||Multicentric|
|Hemangioma||Heterogeneous with interdispersed calcification||Commonly in epicardial layer of myocardium|
|Angiosarcoma||Hypodense nodular lesions||Commonly affect right atrium; frequent extension|
|Rhabdomyosarcoma||Hypodense||Pericardial infiltration rare|
|Lymphoma||Hypodense or isodense||Multiple circumscribed polypoid masses or ill-defined infiltrative lesion|
Axial computed tomography image demonstrating a large paracardiac mass (asterisk) with associated compression of the right atrium (RA). Further workup of the mass revealed a thymoma arising from the anterior mediastinum. Ao, aorta; LA, left atrium; PA, pulmonary artery; RV, right ventricle.
Depending on the size and location of the cardiac mass, CT image acquisition is tailored to obtain the necessary information. Noncontrast CT imaging can provide limited information regarding the nature of cardiac masses, but contrast CT imaging with cardiac gating can better assess the precise location, size, and extent of cardiac masses.
Benign cardiac masses include myxoma, papillary fibroelastomas, lipoma, and rhabdomyoma. Benign tumors tend to affect the left-sided chambers of the heart. Although these lesions are histologically benign, they can act malignantly via secondary effects on the heart and vasculature. Therefore, successful treatment depends on the early detection and characterization of these masses.
Myxomas on CT often demonstrate a distinct, intracavitary sphere, typically with calcification, heterogeneous hypoattenuation consistent with its gelatinous nature,67-69 and neovascularization.70 They commonly demonstrate a narrow base of attachment (somewhat pedunculated), and attachment to the interatrial septum virtually cements the diagnosis.76,71 Functional consequences of large myxomas can be seen in cine cardiac CT in which the tumor mass may prolapse into the ventricles or cause obstruction of the atrioventricular valves.
Papillary fibroelastomas are avascular papillomas lined with endothelium. Depending on the size, location, and mobility, these masses may not be well seen on CT, especially if cardiac gating is not used. However, on CT they often appear as small (<2 cm in diameter), solitary, mobile, pedunculated, hypodense,72 homogeneous valvular, or endocardial masses that flutter or prolapse with cardiac motion.69
Lipomas typically occur in adults, although they can also be seen in children. They generally occur as solitary masses that can arise from the epicardial surface spreading into the pericardial space73 or from the interatrial septum or endocardial surface as a broad base from which they can grow into any of the cardiac chambers.74 Lipomas are seen as encapsulated masses demonstrating the hypodense75 attenuation of fat on CT. There is often lack of contrast enhancement, but use of contrast can increase their conspicuity. In addition, a smooth contour and capsule can further distinguish benign lipomas from the irregular, multilobar liposarcomas.69
Although not a tumor, lipomatous hypertrophy of the interatrial septum can be confused with the truly neoplastic lipoma. Lipomatous hypertrophy results from an increase in cell number, or hyperplasia, seen in obese, elderly individuals as an unencapsulated fatty infiltration, defined formally as any deposit of fat in the atrial septum at the level of the fossa ovalis that exceeds 2 cm in transverse diameter.76 In addition to characteristic sparing of the fossa ovalis seen on echocardiography, this tissue may appear wedge shaped or as diffuse septal thickening on CT.
On CT, fibromas commonly appear as a large solitary, calcified mass within the ventricular myocardium. This is in contrast to other intramyocardial tumors including rhabdomyomas, which are often multicentric, and rhabdomyosarcomas, which are frequently cystic or necrotic.77 On CT, fibromas are commonly hypodense due to the dense, fibrous tissue with bright areas of calcification.78,79
Cardiac rhabdomyomas account for the majority of cardiac tumors seen in infants.71,77 Unlike other cardiac tumors, rhabdomyomas frequently regress over time and thus are treated conservatively. However, complications can result from an obstructive syndrome or from severe arrhythmias.80 On imaging studies, rhabdomyomas can be seen in both right and left ventricular myocardium and interventricular septum. They may be intracavitary or intramural and are often multiple rather than single. On CT, rhabdomyomas appear hypodense to myocardium after contrast administration.
Cardiac teratomas generally occur in infants and children as a predominantly right-sided pericardial mass.81 Although considered benign, these tumors are often accompanied by pericardial effusions, which may progress to cardiac tamponade with subsequent respiratory distress and cyanosis.81,82 However, surgical resection is often curative.83 CT imaging of teratomas demonstrates a heterogenous, multicystic appearance with calcification, often in the form of teeth, and can confirm the diagnosis of teratoma over other tumors.71,77
Cardiac hemangiomas are rare, benign, vascular tumors of the heart. They usually occur in the epicardial layer but can involve all the cardiac chambers. Symptoms are usually the result of tumor compression of surrounding structures or embolization.84 On noncontrast CT, cardiac hemangiomas have a heterogeneous density with occasional interspersed calcification.69 In addition, they enhance intensely with contrast, which may be inhomogeneous due to interspersed calcification and fibrous septa within the mass.85
Malignant Cardiac Neoplasms
Malignant cardiac masses include metastatic neoplasms, primary cardiac sarcomas, and primary cardiac lymphoma. Although no single finding is specific, malignant cardiac tumors commonly affect the right-sided chambers of the heart, demonstrate inhomogeneity of tumor tissue, appear infiltrative, and are associated with pericardial or pleural effusion.86
Most metastases to the heart occur from lung or breast cancer, but they can also occur from melanoma, lymphoma, and leukemia.87-89 Involvement of cardiac structures primarily occurs through the lymphatic pathway, although hematogenous, contiguous, or transvenous extension does occur.90 Cardiac involvement is commonly seen as a late manifestation of primary tumor extension,91 but characteristic vascular involvement signs may help facilitate diagnosis. Pulmonary vein extension may signal bronchogenic carcinoma, inferior vena caval extension can be seen with renal cell and hepatocellular carcinoma, and superior vena caval extension may indicate supracardiac tumors such as thymic carcinomas.92 CT imaging of metastases can demonstrate nodular masses or pericardial thickening often with contrast enhancement due to vascularity of the lesions.93,94 Other common features of malignancy include right-sided involvement, ventricular infiltration, and hemorrhagic pericardial effusion.95
Cardiac sarcomas are extremely rare tumors occurring in less than 0.2% of the population but represent the most common primary malignant cardiac tumor seen in adults.96 These tumors may originate in the epicardium or pericardium, involve the myocardium and cardiac valves, and cause nonspecific signs and symptoms that make clinical diagnosis difficult. There are several subtypes of sarcomas including angiosarcoma, osteosarcoma, fibrosarcoma, malignant fibrous histiocytoma, leiomyosarcoma, myxosarcoma, synovial sarcoma, neurofibrosarcoma, lymphosarcoma, reticulum cell sarcoma, and undifferentiated sarcoma.
Angiosarcoma is a tumor of endothelial cells and represents the most prevalent subtype. These tumors most commonly affect the right atrium; are highly vascular lesions with hemorrhagic, necrotic foci; and frequently invade the pericardium with associated hemorrhagic effusion that can lead to cardiac tamponade.97 On CT, angiosarcomas appear as hypodense irregular or nodular lesions, often arising from the right atrial free wall with heterogeneous enhancement, or in the case of pericardial infiltration, they may appear as pericardial effusion or thickening.98
Rhabdomyosarcomas are striated muscle tumors that represent the most common cardiac malignancy in infants and children.99 These tumors may arise anywhere within the heart, involving any cardiac chamber or valve,100 although pericardial infiltration is rare.71 On CT, these tumors demonstrate low attenuation with a smooth or irregular contour that enhances with contrast.101 Extracardiac extension into the pulmonary arteries, aorta, or valvular structures can be demonstrated with CT.100
Fibrosarcomas consist primarily of malignant fibroblasts and comprise 5% of all primary cardiac tumors.102,103 They commonly affect the left atrium, and valvular involvement is found in as many as 50%. On CT, fibrosarcomas appear as a low-attenuation, often obliterative mass. Fibrosarcomas may infiltrate the pericardium by direct invasion104 or tumor deposition nodules,105 or they may primarily involve the pericardium, appearing similar to malignant mesothelioma.96
Osteosarcomas in the heart consist of malignant bone-producing tumor cells.96 Primary osteosarcomas commonly arise in the left atrium usually accompanied by signs and symptoms of congestive heart failure.106 CT may show dense calcifications within a low-attenuation, left-sided mass.107 However, early lesions may have minimal calcification and can be mistaken for dystrophic calcifications. Other distinguishing features include a broad base of attachment and an aggressive growth pattern with extension into the pulmonary veins or atrial septum or infiltrative growth along the epicardium.108-110
Leiomyosarcoma is a malignant tumor with smooth muscle differentiation. It may arise from the subendocardium of the cardiac chambers but more commonly arises from smooth muscle of the pulmonary veins and arteries and then spreads into the heart.96 CT imaging demonstrates lobulated, irregular, low-attenuation masses.111
Liposarcoma is a malignant mesenchymal tumor that consists of lipoblasts. These tumors are extremely rare.96 They tend to arise in the atria but have been reported to occur in any cardiac chamber, the pericardium, and cardiac valves.112,113 Unlike benign lipomas, liposarcomas have little or no macroscopic fat.69 CT imaging demonstrates a large, multilobular, heterogeneous mass with areas of necrosis and hemorrhage.100
Primary cardiac lymphoma includes lymphoma that is mostly confined to the heart or pericardium,96 as opposed to the more common cardiac spread of non-Hodgkin lymphoma.114 These lymphomas are commonly aggressive B-cell lymphomas.71,115 Although there is increased prevalence in immunocompromised patients, these lymphomas are also seen in immunocompetent patients.115 Cardiac lymphoma may appear as either multiple circumscribed polypoid masses116 or an ill-defined infiltrative lesion.117,118 Cardiac lymphomas are less likely than sarcomas to have necrosis.96 They commonly arise in the right side of the heart but may involve any chamber. Pericardial effusions are common and may be the only finding at the time of imaging. On CT, lymphomas appear hypodense or isodense relative to myocardium and demonstrate heterogeneous contrast enhancement.115,118
Normal Cardiac Structures
Due to the complex nature of the cardiac anatomy and the unique individual variations seen, normal cardiac structures can often be mistaken for cardiac tumors. In particular, fetal remnants (eg, Eustachian valve, Chiari network) or normal variants (eg, prominent trabeculations, false tendons) may give the impression of a cardiac tumor. Given the 3D nature of cross-sectional imaging with CT, differentiation of normal cardiac structures from cardiac tumors can be made. In addition, the distinction between cardiac neoplasms versus other cardiac masses can also be made.
Intracavitary cardiac thrombi probably represent the most common masses seen in cardiac imaging. In patients with atrial arrhythmias or other predisposing factor for atrial blood flow stasis (eg, mitral stenosis), they can frequently be seen along the posterolateral wall of the left atrium or within the left atrial appendage.119 In patients with cardiomyopathy, ventricular thrombi can form in areas of slow blood flow such as ventricular aneurysm or regions with dysfunctional myocardium. On CT, thrombi generally exhibit homogeneous hypodense attenuation after contrast administration.120 Care should be taken to distinguish slow flow with incomplete opacification, which may be seen on first-pass imaging, from true thrombi, which in general will remain hypodense on delayed imaging after contrast administration. (see Fig 5–12)
Intracardiac masses related to infective endocarditis are usually diagnosed with echocardiography in the appropriate clinical setting. However, in cases where the diagnosis is uncertain, CT imaging can aid in excluding a cardiac tumor. In general, vegetations exhibit CT imaging characteristics similar to thrombi. Because vegetations are often nonvascular, they generally do not enhance with contrast administration. Although distinction from cardiac tumor is possible, tissue differentiation between thrombi and vegetations is generally not possible with CT, and accurate diagnosis relies on incorporating the patient's accompanying clinical features and the effect on cardiac structures (eg, location and/or evidence of destruction) (Fig. 5–18).
Multiplanar reformatted computed tomography images demonstrating a bioprosthetic valve in the aortic position with thickened leaflets, large vegetation (black arrow), thickening of the aortic annulus (asterisks), and disruption suggestive of aortic root abscess (white arrowheads).