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REVIEW ARTICLE
Year : 2022 | Volume
: 32
| Issue : 2 | Page : 65-75
Imaging of cardiac masses: An updated overview
Vito Maurizio Parato, Silvio Nocco, Gianluca Alunni, Francesco Becherini, Serenella Conti, Umberto Cucchini, Giovanna Di Giannuario, Concetta Di Nora, Donatello Fabiani, Salvatore La Carrubba, Stefania Leonetti, Vincenzo Montericcio, Antonio Tota, Licia Petrella
Italian Society of Echocardiography and Cardiovascular Imaging, Milan, Italy
Correspondence Address:
Silvio Nocco
Silvio Nocco - SIECVI - 5, Via Giovanni Battista Sammartini, 20125 MILANO
Italy
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jcecho.jcecho_18_22
Studying cardiac masses is one of the most challenging tasks for cardiac imagers. The aim of this review article is to focus on the modern imaging of cardiac masses proceeding through the most frequent ones. Cardiac benign masses such as myxoma, cardiac papillary fibroelastoma, rhabdomyoma, lipoma, and hemangioma are browsed considering the usefulness of most common cardiovascular imaging tools, such as ultrasound techniques, cardiac computed tomography, cardiac magnetic resonance, and in the diagnostic process. In the same way, the most frequent malignant cardiac masses, such as angiosarcoma and metastases, are highlighted. Then, the article browses through nontumoral masses such as cysts, mitral caseous degenerative formations, thrombi, and vegetations, highlighting the differential diagnosis between them. In addition, the article helps in recognizing anatomic normal variants that should not be misdiagnosed as pathological entities.
Keywords: Noninvasive cardiovascular imaging, nontumoral cardiac masses, tumoral cardiac masses
Formations occupying space inside the cardiac structures, such as masses or pseudomasses, are sometimes detected occasionally by a routine echocardiographic examination or by a transthoracic echocardiography (TTE) performed in the emergency room. They require a correct assessment/interpretation that allows to establishing the location, shape, number, size, attachment, mobility, and relationship with adjacent structures.
The study of these cardiac formations initially involves a noninvasive approach, given that biopsy, although still a diagnostic gold standard, presents some nonnegligible problems. Due to its availability and ease of execution, TTE obviously represents the first step, and it can provide us very useful informations even though sometimes the procedure is limited by bad acoustic windows. Transesophageal examination and integration with second-level diagnostic procedures will therefore be necessary. Among these latter, photon emission tomography (PET)/computed tomography (CT) offers good results in the diagnosis of metastatic masses as well as in the confirmation of bacterial endocarditis vegetations. Magnetic resonance imaging (MRI) has proved to be very useful in the differential diagnosis between masses and neomasses, due to the possibility of carrying out a tissue characterization and because of its multiplanar assessment which also allow to provide useful informations to the cardiac surgeon.[1] These modern multimodal imaging techniques, suitably integrated, allow us to evaluate cardiac masses in every aspect, not only for a precise initial diagnosis but also in monitoring their evolution and even posttreatment.
The aim of this article is to focus on the modern imaging of cardiac masses proceeding through the most frequent ones.
MyxomaEpidemiology and pathogenesis
Myxomas are the most common primary cardiac tumor and represent approximately 50% of all benign cardiac tumors in adults.[2] The annual incidence is of 0.5 per million people, and they are most commonly diagnosed in 30-to 50-year-old adults, with a slightly higher incidence in women.[3] They are typically sporadic and isolated, while only in 5%–10% are familial. Cardiac myxomas are intracavitary masses, which are most commonly found in the left atrium attached by a stalk to the fossa ovalis. They might develop also in the right atrium (RA), and other less likely anatomical origins include the atrial free wall and mitral valve leaflet.[4] The pathogenesis is poorly understood: Gene expression and immunohistochemical studies established that cardiac myxoma is a benign neoplasm, and a recent study suggests that tumor cells arise from resident endogenous multipotent cardiac stem cells.[5] Clinical presentation: The clinical presentations of cardiac myxoma are determined by the size, texture, and location of the tumor.[6] In fact, tumors vary widely in size, ranging from some millimeters to 15 cm in diameter. Larger tumors are more likely to have a smooth surface and to be associated with symptoms and signs related to mitral (or tricuspid) valve obstruction with a “tumor plop” being occasionally heard on auscultation [Video 1]. In contrast, smaller myxomas may be friable or villous, and these tend to present with embolic events[7] [Video 2]. In addition, patients with myxomas frequently have constitutional symptoms (fever, weight loss, and fatigue) and laboratory abnormalities mimicking the presence of a connective tissue disease.[8]
Diagnosis
TTE is the tool of choice for the initial evaluation. It can characterize the size, location, and mobility of the atrial mass. Real-time three-dimensional (3D) echocardiography can aid in identifying the stalk origin and analyzing mass heterogeneity using the cropping function and carefully using digital analysis to dissect the lesion.[9] Further evaluation with transesophageal echocardiography (TEE) will help to better visualize the implantation site and profiling mass. TEE allows to demonstrate the hemodynamic effects of the mass, among which the most frequent is mitral inflow obstruction. Cardiac MRI is another helpful diagnostic tool. A heterogeneous appearance on T1 and T2-weighted images are often found due to the composition of myxomas, which tend to have varying amounts of myxoid, hemorrhagic, ossific, and necrotic tissue.[10] Delayed enhancement is normally patchy in nature.[11] When cardiac MRI is not available or contraindicated, cardiac CT is a good alternative. CT can visualize calcification seen in approximately 14% of the patients and analyze arterial-phase contrast enhancement which is usually not present.[12] Even if histopathologic evaluation is necessary to confirm the diagnosis, a transvenous biopsy is usually avoided due to the risk of mobilizing emboli. Treatment and prognosis: Once a presumptive diagnosis of myxoma has been made on imaging studies, early surgical resection should be performed because of embolization risk or cardiovascular complications, including sudden death.[13] Surgical resection is associated with low operative mortality and good long-term outcome. When interatrial septum is the site of attachment, an atrial septal defect can be created during surgical resection. It can be safely repaired by a bovine pericardial patch, as it was demonstrated by Parato et al.[14][Figure 1]. Annual follow-up with TTE is recommended because myxomas might recur, especially in the first 4-year follow-up.[15]
Figure 1: Giant LA myxoma. Left panel: TTE 4-C view showing a round shaped and floating LA giant mass (7 cm × 4 cm) with broad attachment to the entire fossa ovalis, protruding into the mitral valve, with an enlarged LA. Central Panel: Histology of the resected myxoma showing amyxomatous tissue with acid-mucopolysaccharide matrix and polygonal cells. Right panel: surgical specimen of the giant resected myxoma (7 Å~ 4 cm) with attached interatrial septum. LA = Left atrium, TTE = Transthoracic echocardiography Cardiac Papillary Fibroelastoma Cardiac papillary fibroelastomas (CPFs) are the second most common primary cardiac tumors (after myxomas) but the most common cardiac valve tumors and account for 7.9% of benign primary cardiac tumors. Main characteristics: Sex: 55% male; highest prevalence: 6th to 8th decade of life; site prevalence: valvular endocardium; and most commonly involved valve: aortic valve (35%–63%), mitral valve (9%–35%), tricuspid valve (6%–15%), and pulmonary valve (0,5%–8%).[16]
Pathogenesis: Unclear
It has been described as hamartomas, organized thrombi, iatrogenic lesions (postradiation, surgery), giant form of Lambl's excrescence, inflammatory foci (unusual endocardial responses to infection or trauma), and postviral infection lesions. Size: 2–70 mm. Macroscopic anatomy: Typically short pedicle, a gelatinous surface, and multiple papillary projections (sea anemone-like). Microscopically: CPF is avascular and composed of collagen, elastin, and reticulin tissue. It is discovered incidentally in 47% of the patients. They are generally slow-growing tumors but may serve as a nidus, allowing the formation of large superimposed thrombi over a short period of time and, therefore, may result in life-threatening complications. The most common clinical presentation is by embolism to the cerebral, systemic or coronary arterial circulations, followed by heart failure and sudden death. Predictor of death or embolization: Tumor mobility. Need for surgery: It seems to be indicated for patients who have had embolic events, complications that are directly related to tumor mobility (i.e., coronary ostial occlusion), and those with highly mobile or large (>1 cm) tumors. In patients not eligible for surgery, there is a debate between anticoagulation therapy.[17]
Echocardiography
TTE is a useful tool for the initial evaluation of suspected CPF, but TEE is frequently required for a more accurate assessment (only masses measuring less than 2 mm cannot be clearly visualized, with sensitivity decreasing from 89% to 77%). Usually, we observe small, mobile, pedunculated or sessile valvular or endocardial mass, which flutters or prolapses into the cardiac chambers during systole or diastole. Echodensity of the tumor's central collagen core strongly supports the diagnosis and allows it to be differentiated from other intracardiac tumors, vegetations, or mural thrombi. In contrast to the appearance of myxoma, CPF usually appears as a homogeneous tumor. CPF may be found on any endocardial surface, usually located on the left-sided valves and the majority are less than 1 cm in diameter.
Computed tomography
Since the introduction of multi-slice scanners, CT has become the equal of echocardiography in the detection of small moving structures. Furthermore, the growing clinical use of cardiac CT may increasingly uncover CPFs in the near future.
Magnetic resonance imaging
MRI offers soft-tissue characterization and evaluation of valvular function. After administration of extracellular contrast, CPFs display no enhancement in the early perfusion phase but an intense enhancement in the delayed phase. This pattern of delayed enhancement is caused by the content of collagen in fibromas, similar to scar tissue after myocardial infarction [Figure 2]. Contrast-enhanced MRI offers thus a differentiation between tumor and thrombus. Cine-MRI allows an assessment of myocardial and valvular function comparable with echocardiography. However, the major disadvantage of MRI is the reduced spatial resolution compared with CT and echocardiography.[18]
Figure 2: MRI imaging of aortic valve papillary fibroelastomas in form of hyperintense rounded structure on the valve. MRI = Magnetic resonance imaging, T1W = T1-weighted imaging, LGE = Late gadolinium enhancement, T2W = T2-weighted imaging, bSSFP = Balanced steady state free precession, LCA = Left coronary artery Rhabdomyoma Rhabdomyoma is the most common cardiac tumor accounting for more than 60% of the cases in infancy and childhood.[19] Evidence suggests that rhabdomyomas are actually myocardial hamartomas or malformations that are composed of myocytes that resemble fetal cardiac myocytes rather than true neoplasms.[20] However, the true incidence in prenatal life is difficult to estimate as these tumors often regress over time. In addition, tumors can be small and may be difficult to recognize, and not all pregnancies are screened with ultrasound (US). Multiple tumors are highly associated (60%–80%) with tuberous sclerosis[21] and, vice versa, 47% of the tuberous sclerosis patients have cardiac tumors.[22] On histopathology, they appear as nodules of enlarged, glycogen-rich cardiomyocytes with clear cytoplasm, interspersed with “Spider Cells.” Cardiac findings associated with rhabdomyoma are related to the size and position of the tumor and vary widely.[23] They occur with equal frequency in the left and right ventricular and septal myocardium; nearly all are multiple. Approximately, one-third of them also involve either one or both atria. They are usually small and lobulated, with diameters in the range of 2 mm to 2 cm. On echocardiography, they appear as multiple homogenous, well-circumscribed, hyperechoic intramural masses [Figure 3]. 3D and speckle tracking echocardiography highlight the regional reduction in a longitudinal and circumferential strain that is consistent with fatty fibrotic tissue of the rhabdomyomas.[24] On MRI, they are isointense to slightly hyperintense relative to myocardium on T1-weighted images and hyperintense on T2-weighted images. They may enhance less than myocardium after administration of intravenous contrast material.[25] MRI is often used in rhabdomyoma to evaluate the brain, liver, and kidneys for evidence of tuberous sclerosis. The tumors can be clinically silent or cause hemodynamically significant obstructions, heart failure, cerebral embolization, arrhythmias, and sudden cardiac death. Symptoms can be due to a variety of anatomic prerequisites including displacement, mobility, space occupation, coronary infiltration, and flow obstruction.
Figure 3: Transthoracic echocardiography of left ventricle rhabdomyoma. It appears as multiple homogenous, well circumscribed, hyperechoic intramural masses Lipoma Second, in incidence to myxoma among benign cardiac tumors, lipoma is, however, a rare cause of cardiac mass in absolute terms. It is often asymptomatic and incidentally discovered during routine examinations performed for other reasons. Sometimes, it is accompanied by symptoms that can be rapidly worsening and life-threatening (like syncope or arrhythmias), depending on size and position. Lipoma may arise more frequently from subendocardium but can have also an intramural development or arise from epicardium (in this last case it may become particularly large).[26] Echocardiography is the front-line screening method: Lipoma appears like a homogeneous echogenic structure that, in case of intracavitary development, can be better delineated with contrast. As with other benign tumors, however, it presents limited perfusion after contrast enhanced US examination, so that other imaging modalities are necessary for defining the true nature. At cardiac CT, lipoma shows a low-density signal, equivalent to subcutaneous fat. Usually, it has a well-defined fibrous capsule, a feature that allows to distinguish it from lipomatous hypertrophy of the interatrial septum that seems to be related to a metabolic disorder [Figure 4]. The wide imaging field of CT allows to demonstrating the anatomic relationships of lipoma with surrounding chest structures, which is essential information in surgical planning. Tissue characterization is accurately defined by MRI. Cardiac lipoma shows increased intensity at T1-weighted images and typically the loss of signal with the corresponding fat-saturation sequence. After gadolinium contrast, no enhancement is detected in the early and late phase. Cardiac MRI is therefore fundamental to describe mass morphology and possible infiltration on the corresponding heart chambers.[27] Again, echocardiography has a well-established role in assessment of mass effect on cardiac hemodynamics. Despite the usually slow-growing, cardiac lipoma should be followed-up over time regardless of treatment strategy (surgical or conservative). In general, cardiac MRI appears to be the best choice, being CT a good alternative (with attention to cumulative radiation exposure).[28]
Figure 4: Lipomatous hypertrophy of the interatrial septum at transthoracic echocardiography and MRI imaging. MRI = Magnetic resonance imaging Hemangioma Hemangiomas are extremely rare, accounting for 5%–10% of benign cardiac tumors. They are classified histologically according to the size of their vascular channels into three types: Capillary, cavernous, and arteriovenous. They may occur in any part of the heart but more commonly are found in the lateral wall of the left ventricle (LV), the anterior wall of the right ventricle (RV), or the interventricular septum. Most often, they are incidentally detected. If symptomatic, cardiac hemangioma can present with arrhythmias, pericardial effusion, congestive heart failure, right ventricular outflow tract obstruction, coronary insufficiency, and sudden death. Diagnosis is usually made by echocardiography, MRI, and computed tomography (CT).
Considering that cardiac hemangioma is not necessarily an indication for surgery, as spontaneous regression and successful medical treatment with corticosteroids have been reported, better noninvasive characterization is worthwhile. Differential diagnosis includes thrombi, myxoma, lipoma, fibroma, cysts, and malignant tumors, such as angiosarcoma.
Echocardiography
Hemangiomas appear as hyperechogenic, well-demarcated masses, ranging from 1 to 8 cm in size [Video 3]. In 30% of the cases multiple tumors are described.
Computed tomography
CT images may demonstrate a heterogeneous mass with foci of calcifications and avid enhancement after intravenous contrast administration. MRI: Isointense signal compared with myocardium on T1-weighted images and homogeneously high signal on T2-weighted images are typical signs for cardiac hemangioma.
AngiosarcomaAngiosarcoma is the most common primary cardiac malignancy of adulthood, accounting for approximately 9% of primary cardiac tumors. It is more common in men and occurs over a wide age range. Unlike other sarcomas, about 80% of the angiosarcomas involve the right atrial free wall and may extend to the pericardium, causing right ventricular inflow tract obstruction, pericardial tamponade, and lung metastasis.[26]
Pulmonary artery sarcomas tend to be confined to the pulmonary artery, often causing severe right heart failure and metastasizing later than right heart sarcomas. Treatment of cardiac sarcoma is challenging given the high likelihood of advanced disease at the time of diagnosis, whether it be extensive local disease or distant metastases. The treatment of choice is complete surgical resection. Surgery is feasible only if the benefits of excision outweigh the extent of myocardial tissue loss. Complete surgical resection has been shown to offer an improved median survival of up to 24 months, which compares to all other patients who had a median survival of up to 10 months.[29]
Echocardiography (especially radiotherapy-3D) is an excellent tool to assess the hemodynamic effects of the mass [Figure 5].
Figure 5: 3D trans-esophageal echocardiography showing right atrial angiosarcoma. 3D = Three-dimensionalThe extension of an intracardiac or pericardial mass in a cardiac wall is usually a marker of malignancy. Echo-contrast agents are useful to confirm the presence of contrast enhancement, which is a marker of vascularity, and to assess the myocardial infiltration.
Cardiac CT provides excellent high-resolution anatomic information about local invasion. Primary cardiac angiosarcoma often presents as a low-attenuation lesion with heterogeneous centripetal enhancement after intravenous contrast administration. Yu et al. argued that this phenomenon can be attributed to the lack of vascularity in the mesenchyma of angiosarcoma and abundant vascularity in the parenchyma.[30]
Cardiac MRI is a complementary imaging tool that provides further insight into tissue characteristics while also it evaluates the hemodynamic effects, invasion, and impact on the surrounding structures. Due to the propensity of angiosarcomas for necrosis and hemorrhage, they typically have heterogeneous signals on cardiac MRI. On T1-weighted fast spin echo (FSE) sequences, tumors are typically low-signal, and T2-weighted FSE images typically show increased signal and central areas of hyperintensity, consistent with hemorrhage and necrosis, and areas of moderate signal intensity in more peripheral regions. Due to their high vascularity, strong signal enhancement is seen after the administration of I. V. gadolinium.[31]
Cardiac MetastasesOnly 5%–6% of the primary tumors are malignant, most commonly sarcomas, lymphomas, and mesotheliomas. Cardiac metastases are up to 40 times more common than primary cardiac tumors. They are found in 6%–20% of autopsies of patients with malignant neoplasms.[32] The most common neoplasms that metastasize to the heart are malignant melanoma, lymphoma, and leukemia, but the relative numbers are greater with breast and lung cancers, reflecting the most common incidence of these cancers. Cardiac metastases are usually found late and are rarely seen as the first site of metastases.[33] The orders of frequency of neoplasms to metastasize to the layers of the heart are epicardium (75.5%), myocardium (38.2%), and endocardium (15.5%). Infrequency of cardiac metastasis may be due to some factors: The strong action of the myocardium, metabolic peculiarities of striated muscle, rapid blood flow through the heart, and lymph flow moving away from the heart.[34] Malignant tumors can metastasize to the heart by one of four different pathways: Lymphatic, hematogenous, direct extension, and transvenous extension through the superior or inferior vena cava (IVA).[35] Lymphatic spread often gives rise to pericardial metastases. The hematogenous spread has a propensity to migrate to the myocardium. Malignant melanoma, lymphoma, leukemia, and soft-tissue sarcoma are some of the neoplasms that spread through the hematogenous route. Tumors that are in close proximity to the heart, such as bronchial, breast, and esophagus, most often spread by direct extension and give rise to pericardial disease.
Diagnosis of cardiac metastasis is done primarily with the use of echocardiography and then with other imaging techniques (i.e. CT or MRI).[36] Echocardiography can provide information about cardiac tumors with regard to size, location, and response to treatment.[31] Cardiac MRI and CT provide complementary information and are able to identify extracardiac infiltration and also provide further tissue characterization. CT and MRI provide also valuable information in regards to anatomical definition for preoperative planning.
Echocardiography is the first-line technique to detect cardiac metastases. Two-dimensional (2D) echocardiography remains the primary diagnostic modality. Additional use of newer echocardiographic techniques such as 3D, strain, and contrast echocardiography better characterize tumor morphology, tissue characteristics and vascularity respectively. Frequently, transthoracic echocardiogram reveals secondaries in the form of pericardial effusion with or without tamponade, often associated with large intrapericardial masses.[37] Sometimes, transthoracic echocardiogram can detect secondaries in the form of large intracavitary masses. The metastatic masses can be so large to occupy the entire cardiac cavity, as it happened in the case report published by Crosca et al.[38] in which authors found a giant mass (7 cm × 4 cm) originating from RV apex with RV cavity obliteration, floating and protruding into RA through the tricuspid valve, with ellipsoid shape and “soft” composition [Video 4]. The mass provoked cardiogenic shock, and it was found to come from an adrenal carcinoma through inferior vena cava.
For metastasis to the right side of the heart, a transesophageal echo-guided biopsy is used for histological analysis.
Cardiac magnetic resonance (CMR)[39] imaging provides a high-resolution assessment of cardiac structure and function. Of particular relevance to cardiac metastases, CMR provides a reproducible cross-sectional assessment of cardiac geometry, enabling a comprehensive assessment of metastases location and functional sequelae. Beyond anatomic imaging, CMR enables tissue characterization of cardiac masses based on vascular supply. Differentiation of neoplasm from thrombus based on contrast uptake has been validated in relation to histopathology findings. Tissue characterization imaging of masses has also been shown to stratify clinical outcomes. CMR is increasingly used to assess cancer patients and has been used to study mixed patient cohorts with benign and malignant neoplasms. To date, CMR has not been routinely used to study cardiac metastases among patients with systemic cancer. Usually, it is used for selected cases.
CT is particularly useful for pericardial metastases.[32] For isolated or associated pericardial effusions, CT attenuation measurements can characterize pericardial fluid, with values close to water likely representative of simple fluid and those above water possibly representing malignant or hemorrhagic fluid.
Particularly, due to the implementation of faster CT scanners, cardiac metastases of malignant melanoma can be detected using routine whole-body staging protocols enabling exact delineation of cardiac structures even without electrocardiographic (ECG)-gating. Yet, the frequent presence of cardiac metastases in autopsy studies and rare detection by CT examinations suggest a significant underestimation of cardiac metastases in malignant melanoma by routine staging techniques.[40],[41] PET/CT scan can demonstrate cardiac metastases in the form of increased cardiac 18-fluoro-deoxy-glucose (18F-FDG) uptake in LV that should be differentiated from papillary muscle hypertrophy or thrombus.[42]
Cardiac CystsPericardial cysts
The pericardial cysts are uncommon benign congenital or acquired diseases of the pericardium or anterior mediastinum. They can be a result from aberrations in the formation of celomic cavities. They can occur as sequelae of previous pericarditis or an echinococcosis infection.[43] The cyst wall is composed of connective tissue and a single layer of mesothelial cells and usually contains clear fluid. Their etiology can be congenital or inflammatory. Rheumatic carditis or infection (bacterial like tuberculosis and echinococcosis), postcardiac surgery, or traumatic events can be the cause. The identification can be made with: (1) echocardiography with evidence of anechogenic space in the pericardium or (2) cardiac tomography scan in which the cysts appear as a well-defined, nonenhancing, fluid-attenuation, rounded mass next to the pericardium; or (3) MRI in which the signal characteristics are those of fluid and include: T1 mapping with typically low signal (occasionally can be a high signal if contains proteinaceous material), T2 mapping with a high signal. T1 C+ (Gd): No enhancement. They are benign lesions, and often the patients are asymptomatic, and surgical resection or aspiration may be performed for symptomatic selected cases [Figure 6].
Figure 6: A pericardial cyst located in the anterior mediastinum at TTE and MRI imaging. TTE = Transthoracic echocardiography, MRI = Magnetic resonance imagingHeart cysts
Congenital blood cysts of the heart valves are found most commonly on the tricuspid and mitral valves of fetuses and infants. Usually, they haven't a clinical relevance, but sometimes, mainly the mitral valve cysts located on the anterior leaflet, can cause left ventricular outflow tract obstruction and heart failure and need surgical resection.[44] The cardiac hydatid cyst can lead to various cardiac symptoms in endemic areas. The most commonly observed site of infestation within the heart was the LV, and this can be explained by this cardiac site's high vascularization and muscle bulk [Figure 7]. The presence of cysts in the pericardium was also common, due to partial rupture of the hydatid cyst, but most hydatid cysts are located in the myocardium near the pericardium, while the involvement of the RV is less frequent. Although at first asymptomatic, hydatid cysts of the heart can cause symptoms at later stages, which will vary depending upon the location of the infestation within the heart. Echocardiography is the most sensitive and specific tool to diagnose hydatid cysts in terms of location, size, presence of scolices, and to calculate the pressure on the vital parts of the heart. Other available important tools of investigation are cardiac CT-scan and MRI for a better demarcation and lineation of the cysts.[45] The treatment is reserved only to symptomatic patients with hemodynamic alterations.
Figure 7: Giant hydatic cist inside LV at TEE (courtesy of Anita Sadeghpour). LV = Left ventricle, TEE = Transesophageal echocardiography Intracardiac Thrombi Left ventricular thrombi
TTE is the diagnostic modality most commonly used for assessing the presence, size, and shape of left ventricular thrombi (LVT). LVT are recognizable as echodense mass with margins, distinct from the endocardium, varying considerably in size, texture, and mobility.[46] Large, mobile thrombi may be morphologically indistinguishable from tumor masses. The most useful discriminating feature is the coexistence of underlying abnormalities of regional or global left ventricular wall motion. According to Virchow's triad, the left ventricular thrombus must be suspected when it appears to be contiguous to areas of LV wall akinesis or dyskinesis, especially in patients with a large infarct size or LV aneurism and most commonly located in or near the apex or in those with a marked sistolic dysfunction [Video 5].
Newly formed thrombi are usually highly mobile and protruding into a ventricular cavity, whereas older thrombus tends to have a smooth cavitary surface and is typically less mobile. More chronic thrombus may show calcifications and central cavitation.[46]
Yet, despite a specificity of 95% to 98%, a low sensitivity of approximately 21% to 35% for LV thrombus diagnosis suggests that many thrombi will be missed using TTE alone.
The addition of intravenous contrast to TTE may improve delineation of the LV endocardial border, facilitating improved sensitivity. The utility of TEE for diagnosing LV thrombus is limited because the apex is often not well visualized.
The most accurate modality for diagnosing LV thrombus is delayed-enhancement CMR, with a sensitivity of 82% to 88% and specificity of 99% to 100% (relative to surgical or pathological validation). Gadolinium contrast will demonstrate uptake within infarcted and, to a lesser extent, viable myocardium, but not in thrombi owing to their avascular composition.[47]
Left atrial thrombi
Transesophageal echocardiography (TOE) has been the standard of care when the primary aim is to exclude left atrial (LA) and left atrial appendage (LAA) thrombus prior to cardioversion and pulmonary vein isolation. Computed tomographic angiography is a reasonable alternative, with excellent sensitivity and specificity comparable to TEE, in patients in whom the risks associated with TEE outweigh the benefit.[48]
Further, there was no significant difference in the sensitivity and specificity of Cardiac Computed Tomography (CCT) versus CMR, suggesting that both modalities can be considered reasonable alternatives to TOE in the identification of LAA thrombi. CMR imaging may be especially beneficial when TOE and CCT cannot be performed.
These types of thrombi, usually located in the appendages, are most commonly identified in the setting of atrial fibrillation or mitral stenosis [Video 6]. The presence of spontaneous echo contrast provides important supportive evidence to the thrombotic nature of an intracardiac mass. Thrombi in the absence of underlying cardiac diseases are distinctly less common, but may occur in the setting of hypercoagulable states such as autoimmune disease, pregnancy, and certain malignancies. These thrombi may be difficult to distinguish from myxoma on the transthoracic study. Several characteristic features may assist in the distinction between thrombi and myxomas. For example, myxomas are rarely calcified and usually present as a solitary mass; left atrium is the most common site, and an attachment stalk is often identified in or near the fossa ovalis.[47] Old and well-organized thrombi may have a robust fibrotic coating and a central hemolytic area, giving them a “doughnut appearance” [Figure 8].
Figure 8: 3D-TEE image of a giant (4 cm × 4 cm) left atrial old and organized thrombus with robust fibrotic coating and central hemolytic area. 3D = Three-dimensional, TEE = Transesophageal echocardiographyCMR offers superior advantages in the detection of cardiac thrombi. The thrombus in cine-MR image can appear as iso or hypointense. Acute thrombus usually is hyperintense on T1-and T2-weighted imaging due to oxygenated hemoglobin. Hemoglobin is transformed into methemoglobin in subacute thrombus, leading it to be hyperintense on T1-weighted imaging and hypointense on T2-weighted imaging. In the chronic period, the thrombus is replaced by fibrous tissue. As the fibrosis content increases, the thrombus is characterized by hypointensity on T1-and T2-weighted imaging. It has been shown that the thrombus does not uptake the gadolinium contrast medium, and there is no enhancement on early gadolinium enhancement and late gadolinium enhancement imaging. Peripheral enhancement can be occasionally seen in chronic organic thrombus due to fibrotic components.[49]
Right ventricular thrombi
Right ventricular thrombus (RVT) is an infrequent and most likely under-diagnosed life-threatening condition. There are two major types of RVT. Type A is a serpiginous and highly mobile thrombus that mostly originates in the peripheral veins in the context of pulmonary embolism, and it is associated with high mortality. Type B is believed to develop in situ, is not mobile and could be related to underlying cardiac abnormalities.[50]
While TTE and transoesophageal echocardiography reach high sensitivity and specificity for detection of left ventricular thrombus, sensitivity and specificity for RVT appear to be lower [Video 7].
Echocardiography is not able to provide additional information for the differential diagnosis of cardiac masses. In contrast, CMR offers accurate and nonexaminer-dependent images.
The thrombus size's reduction after anticoagulation therapy can confirm the differential diagnosis toward a cardiac tumor.[50]
Right atrial thrombi
Atrial thrombi are infrequently seen on transthoracic study, but have been observed in the setting of pulmonary embolism. The differential diagnosis of RA masses includes benign or malignant primary or metastatic tumors, tricuspid valves, and vegetations. RA thrombi are in transit having migrated from the venous system to the heart, in this case, take the tubular form.
Patients with mechanical valves, right-sided pacemaker leads, ventricular or atrial septal closure devices, and central venous lines are also at higher risk for RA thrombi.[51]
RA thrombi are most commonly diagnosed with TTE. However, in a study of 16 patients with RA thrombi, size, mobility, and site of attachment of thrombus were better defined by TEE than by TTE[51][Figure 9].
Figure 9: Transthoracic and transesophageal echocardiography images showing a right-sided large thrombus through the tricuspid valve Vegetations Valve endocarditis (VE) is one of the most important life-threatening infectious diseases, and its timely diagnosis, antibiotic treatment, and management of complications is critical to optimal outcomes, both on native (NV) and prosthetic valves (PV). The presence of an echocardiogram generating a suspicion of infective endocarditis, such as valvular or mural vegetations or perivalvular abscesses, is one of the major standardized Duke criteria, thus the imaging evaluation plays a key role in the diagnosis of this disease.
Echocardiography remains the first choice in every suspect of VE, due to is wide availability, low cost, rapid interpretation, and safety. In suspected NV endocarditis, TTE is moderately sensitive (75%) and specific (more than 90%) for detection of vegetations. In patients with an equivocal or negative TTE, but high clinical likelihood of infective endocarditis, TOE is necessary and has a sensitivity of more than 90%. A normal TOE strongly predicts the absence of disease, but if clinical suspicion is high, the exam should be repeated 7–10 days later. Moreover, the evaluation of the PV could be more arguing, and the sensitivity of TTE is lower (36%–69%), therefore TOE is usually necessary in all cases of suspected PV endocarditis for detection of vegetations, perivalvular abscess, prosthesis dysfunction or dehiscence, fistulas, or unexpected and premature structural degeneration of the valve.[51] Moreover, 3D echocardiography is a complementary modality which provides valuable information on the assessment of the vegetation size and location, destructive changes, perforations, abscess characterization, prosthetic dehiscence, and associated regurgitant jets [Videos 8 and 9].
Cardiac computed tomography
Increasing data have accumulated on the role of CCT in VE with high accuracy for large vegetations, perivalvular complications, and for exclusion of coronary artery disease to avoid invasive angiography. CCT can further help to clarify the etiology of infective prosthetic valve dysfunction, especially in cases of malposition, abscess, leak, vegetation or mass, for its excellent correlation with TOE.
Cardiac magnetic resonance imaging
MRI can be of help in visualization of valve or mural vegetations that may not be visible on dark-blood imaging, while they are better depicted on cine-MRI, manifesting as low-signal areas following the cusps. The differentiation from thrombus may be difficult, because both usually do not show contrast enhancement. However, a peripheral rim of late gadolinium enhancement has been observed in vegetations and may indicate irreversible myocardial damage or fibrosis. Conversely, the role of MRI for diagnosis of PVE is limited for the incompatibility with some implantable cardiac devices, reduced availability and significant artifacts caused by metallic leaflets.[52],[53]
PET 18F-FDG PET/CT. 18F-FDG PET/CT is a useful complimentary imaging modality for the diagnosis of VE, especially in challenging cases related to PV.[54] Thus the presence of abnormal activity of 18F-FDG PET/CT around the perivalvular region of a PV has become a new major criterion for diagnosis of VE and has significantly increased the sensitivity of the modified Duke criteria from 70% to 97% without affecting the specificity. However, it is useful to know that the reactive inflammatory activity in the early stage after prosthesis implantation could create false positive findings, thus 18F-FDG PET/CT is advisable >3 months after prosthesis implant.
Mitral Annulus CalcificationMitral annulus calcification (MAC) is a chronic, degenerative process in the fibrous base of the mitral valve. It more commonly affects posterior than anterior annulus. Echocardiography is the more frequent method to demonstrate MAC.[55] The 2D echo-technique clearly demonstrates the localization of MAC to the angle between the LV posterior wall and the posterior mitral leaflet usually visualized as an echo-dense, shelf-like structure with an irregular, lumpy appearance involving the mitral valve annulus, with associated acoustic shadowing [Video 10]. Cardiac CT is a useful tool to predict the extent and location of MAC and to quantify MAC objectively in order to assess the severity of this pathological entity.[55]
Caseous calcification of the mitral annulus (CCMA) is a rare variant of Mitral Annulus Calcification (MAC). Since most cardiologists are unfamiliar with CCMA, it is commonly misdiagnosed as an abscess, tumor or infective vegetation on the mitral valve. CCMA represents a rare evolution of a calcified mitral ring due to caseous transformation of the inner material.
Echocardiography shows a large, round, echo-dense mass with smooth borders situated in the periannular region, with no acoustic shadowing artifact. It contains central areas of echo-lucencies resembling liquefaction. It may appear as a semilunar mass in the parasternal short-axis view. The mass is usually located in the posterior region, at the junction between the left atrium and the LV, bulging into the LA cavity or into the adjacent left ventricular posterior wall.
On CT scan, CCMA appears as a well-defined oval or crescent-shaped hyperdense mass with peripheral calcification, usually along the posterior mitral annulus. It has very high Hounsfield units, and lacks contrast enhancement. The central hyperdensity is thought to be secondary to the liquefactive material that fills the center of the mass.[56]
Cardiac MRI is considered to be the technique of choice in doubtful cases. Findings of CCMA on cardiac MRI include a well-defined mass with hyperintense center and hypointense rim, discrete from the adjacent myocardium and posterior mitral valve on T1-weighted fast spin-echo imaging. A similar centrally hyperintense mass with a peripheral rim of hypointensity is also visualized with T1-weighted spoiled gradient-echo imaging techniques. On T2-weighted MRI sequences, CCMA appears as a mass devoid of a central signal but with a ring of high intensity compared with the surrounding myocardium.[56]
Normal Anatomic Variants and PitfallsSeveral anatomic variants can be occasionally detected and should not be misdiagnosed as pathological entities. The most common ones are summarized in the latest EACVI recommendations on diagnosis of cardiac sources of embolism.[57]
The atria are particularly prone to normal anatomic variants. The Eustachian valve More Details is a semilunar musculo-membranous remnant of the valve of IVC, which direct oxygenated placental blood towards left atrium during intrauterine life. It can be appreciated at the posterior margin of IVC. Considered a variant of the Eustachian valve, the Chiari network appears as a free-floating fenestrated reticulum with variable attachment sites along the ridge connecting IVC and interatrial septum [Figure 10]a, whereas crista terminalis is a dense muscular ridge separating the smooth and trabeculated part of the RA. A fat deposition within the interatrial septum is also known as lipomatous hypertrophy. The fossa ovalis is typically spared with a classic hourglass appearance. Another variant involving interatrial septum is atrial septal aneurysm, defined as a septal bulging >10 mm in either right or left atrium. LA appendage examination allows the visualization of pectinate muscles that should be distinguished from thrombotic formations. Other anatomic variants within the LA are the suture line following cardiac transplants and the so-called Coumadin ridge (the ridge between the upper pulmonary vein and the LA appendage).
Figure 10: (a) Apical 4-chamber view showing Chiari network within the RA (asterisk). (b) Moderator band (arrow). (c) Pacemaker lead crossing RA and RV (arrows). (d) Parasternal long axis view showing calcification of posterior mitral valve leaflet (asterisk). (e) Reverberation artifact projected into the LV (arrow). LA = Left atrium, LV = Left ventricle, RA = Right atrium, RV = Right ventricleCalcifications of mitral annulus and leaflets are frequently seen in elderly patients and rarely associated with relevant valvular disease [Figure 10]d. Lambl's excrescences, typically located on the ventricular side of the aorti
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