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AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY |
1 Department of Radiology, University of Michigan Medical Center, Ann Arbor, MI
48109-0030.
2 Department of Radiology, University of Washington, Box 354755, 4245 Roosevelt
Way NE, Seattle, WA 98105.
Received February 16, 2007; accepted after revision February 16, 2007.
Address correspondence to F. S. Chew
(fchew{at}u.washington.edu).
The educational objectives for this self-assessment module on imaging of cardiac masses and myocardial disease are for the participant to exercise, self-assess, and improve his or her knowledge of imaging and the clinical features of cardiac masses and myocardial disease, with emphasis on CT and MRI.
Keywords: cardiac masses • MRI • myocardial disease
INTRODUCTION
This self-assessment module on imaging of cardiac masses and myocardial disease has an educational component and a self-assessment component. The educational component consists of six required articles that the participant should read. The self-assessment component consists of 10 multiple-choice questions with solutions. Links to all of these materials are available on the ARRS Website (www.arrs.org). To claim CME and SAM credit, each participant must enter his or her responses to the questions online.
EDUCATIONAL OBJECTIVES
By completing this educational activity, the participant will:
REQUIRED READING
(available at www.arrs.org)
INSTRUCTIONS
| QUESTION 1 Which of the following is the most common intracavitary cardiac mass?
QUESTION 2 Each of the following statements regarding cardiac myxomas is TRUE EXCEPT:
QUESTION 3 Each of the following statements regarding the imaging of cardiac masses and pseudomasses is TRUE EXCEPT:
QUESTION 4 Regarding cardiac masses, which one of the following statements is TRUE?
QUESTION 5 Each of the following statements regarding angiosarcoma of the heart is TRUE EXCEPT:
QUESTION 6 Regarding metastases to the heart, which of the following statements is TRUE?
QUESTION 7 Which of the following imaging techniques is most sensitive for the detection of small mural thrombi in the left ventricle?
QUESTION 8 Which of the following is the most common chamber for an intracavitary thrombus?
QUESTION 9 Which of the following statements is TRUE concerning MRI of cardiomyopathy?
QUESTION 10 Which of the following possible MRI findings is most suggestive of myocarditis?
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Solution to Question 1
Cardiac thrombi are overall the most frequent cardiac masses, mainly resulting from regional or global impaired wall motion (e.g., after myocardial infarction or in dilated cardiomyopathy) or from arrhythmia (atrial fibrillation) [1]. Option D is the best response. Metastases to the heart are more common than primary cardiac tumors. Option C is not the best response. Most primary cardiac tumors are benign myxomas. Option A is not the best response. Primary malignant cardiac tumors are rare and are usually sarcomas [2]. Option B is not the best response. Cardiac lipomas are much less common than myxomas; lipomas account for approximately 14% of benign cardiac tumors [3]. Option E is not the best response.
Solution to Question 2
Myxomas are the most common intracavitary primary neoplasm of the heart. Option E, which is true, is not the best response. Although the preferential location is the left atrium (75% of cases), 20% of myxomas occur in the right atrium [4]. Option B, which is true, is not the best response. A female preponderance is recognized. Option A, which is true, is not the best response. Myxomas can be familial in origin; they are sometimes associated with a specific clinical syndrome, Carney's syndrome, which consists of the clinical combination of abnormal pigmentation, cutaneous myxomas, and endocrine overactivity [5]. Option C, which is true, is not the best response. Although certain features, such as the presence of a stalk, attachment to the fossa ovalis, and location in the left atrium, can suggest a myxoma, there are no definite pathognomonic imaging features [4]. Option D, which is false, is the best response. The MR signal intensities of a myxoma depend on the composition of the mass and can overlap with those of other benign and malignant cardiac tumors and with thrombi. Most myxomas show heterogeneous signal intensity and enhancement due to their varying components of myxoid, hemorrhagic, cystic, calcified, ossified, and fibrous tissue. In the typical case, signal intensity increases on T2-weighted images with heterogeneous enhancement after contrast administration.
Solution to Question 3
The delayed-enhancement MR technique is particularly sensitive for detecting thrombi, which are seen as dark structures surrounded by contrast-enhanced blood [6]. Option A, which is true, is not the best response. Soft-tissue sarcoma is the most common primary malignant neoplasm of the heart, with the angiosarcoma subtype being the most common entity. Most cardiac angiosarcomas arise in the right atrium and present as single or multiple nodules, filling the right atrium or infiltrating the myocardium and pericardium [1]. Option B, which is true, is not the best response. Nodular thickening of the posterior right atrial wall is a common finding on MR images and may resemble a mass lesion [7]. Anatomically, this nodular thickening corresponds to the crista terminalis, which marks the embryologic division between the portion of the right atrium derived from the sinus venosus and that derived from the embryonic atrium. Option C, which is true, is not the best response. The crista terminalis extends as a prominent muscular ridge between the orifices of the superior and inferior venae cavae along the posterior lateral aspects of the right atrium. Lipomatous hypertrophy of the interatrial septum is a benign condition characterized by fat accumulation in the interatrial septum in continuity with the epicardial fat. Typically, there is sparing of the fossa ovalis, producing a dumbbell-shaped entity [8]. Option D, which is false, is the best response. Papillary fibroelastomas are rare benign cardiac tumors; however, they are the most common primary tumor of the cardiac valves [9]. They are usually small tumors that are pedunculated and mobile and are discovered accidentally or when neurologic or cardiologic complications occur because of embolic phenomena. Option E, which is true, is not the best response.
Solution to Question 4
Mural thrombus resulting from myocardial ischemia, valvular disease, dysrhythmias, or hypercoagulable states, is the most common intracavitary cardiac mass [10]. Tumors are much less common than thrombi. Malignant tumors are less common than benign tumors. Option A is not the best response. Among neoplastic cardiac lesions, metastatic tumors are 20-40 times more common than primary cardiac tumors [10]. Option B is not the best response. Although up to 70% of patients with melanoma may eventually have cardiac metastases, given the greater overall prevalence and proximity to the heart, lung cancer is statistically the most frequent source of metastases to the heart, followed by nonsolid tumors (i.e., leukemia, lymphoma, Kaposi's sarcoma) and breast cancer. Option C is not the best response. Given the presence of mineralized osteoid matrix in osteosarcoma metastases, CT would have an advantage over MRI in detection. With this exception, MRI, with its superior contrast of soft tissues, is generally the technique of choice when evaluating for cardiac metastases. Both CT and MRI offer advantages over echocardiography when evaluating for cardiac metastases because of the larger field of view and evaluation of contiguous thoracic structures [11]. Option D is not the best response. Rhabdomyoma is the most common primary heart tumor in children [10]. Rhabdomyomas often occur in association with tuberous sclerosis, von Hippel-Lindau disease, and neurofibromatosis type 1. Option E is the best response.
Solution to Question 5
Angiosarcomas are aggressive lesions that arise most commonly in the right atrium (80%). On imaging, they are typically hemorrhagic masses that frequently show right atrial wall invasion with extension into the pericardium or an adjacent chamber [12]. Patients often present with right heart failure or cardiac tamponade. When angiosarcomas extend from the heart into the pericardium and bleed, they may cause cardiac tamponade. Options A, B, and C are true, and are therefore not the best responses. Angiosarcoma occurs approximately twice as frequently in men as in women and is the most common cardiac sarcoma in adults. Option D is not true and is therefore the best response.
Solution to Question 6
Metastases to the heart usually occur in the context of wide-spread metastatic disease. Option A is not the best response. Metastases may reach the heart through hematogenous dissemination, direct extension, retrograde extension through lymphatics, or transvenous extension. The most common situations in which transvenous extension occurs are renal cell carcinoma extending through the inferior vena cava and lung carcinoma extending through the superior vena cava or a pulmonary vein [13]. Option B is true and is the best response. Metastases are typically distinguishable from thrombi on imaging because thrombi are intracavitary, do not show aggressive features such as cardiac wall invasion, and do not enhance on MRI after gadolinium injection. Option C is not the best response. Lung cancer usually metastasizes to the heart and pericardium by direct extension. The most common primary tumors that metastasize to the heart hematogenously are melanoma and hematologic malignancies such as lymphoma. Option D is not the best response.
Solution to Question 7
Two-dimensional transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are the most commonly used techniques for the initial identification and follow-up of left ventricular thrombi. However, they are limited in sensitivity and specificity for detecting small mural thrombi adhering to the wall of the left ventricle. Options A and B not the best responses. Although contrast-enhanced CT may reveal left ventricular thrombi as low-attenuation masses, it is limited in its contrast resolution compared with MRI, and small mural thrombi may be indistinguishable from adjacent myocardium. Option C is not the best response. Myocardial delayed contrast-enhancement MRI has been shown to be the most accurate technique for the detection of small mural thrombi [14-16]. Option D is the best response.
Solution to Question 8
Although the left atrium is the most common chamber for an intracavitary thrombus, it may occur in any chamber, within the atrial appendages, or within a ventricular aneurysm. Option C is the best response. The imaging appearance on MRI is variable, depending on the age of the clot and the stage of hemoglobin degradation [10]. Unlike tumors, thrombi do not enhance, although there may occasionally be a thin rim of enhancement that corresponds to a surrounding fibrinous pseudocapsule.
Solution to Question 9
In ischemic dilated cardiomyopathy, regional ventricular wall thinning occurs in one or more locations; in nonischemic dilated cardiomyopathy, the ventricular wall thickness is uniform [10]. Option A is not the best response. Hypertrophic cardiomyopathy is characterized by variably distributed thickening of the left ventricular wall without dilatation of the chamber. Option B is not the best response. Restrictive cardiomyopathy can be distinguished from constrictive pericarditis on MRI, on the basis of whether the pericardium is of normal thickness (cardiomyopathy) or of abnormally increased thickness (pericarditis). The distinction has management implications because constrictive pericarditis may be treated surgically. Option C is the best response. Blooming decreased myocardial signal intensity on gradient-recalled echo sequences in the clinical setting of restrictive cardiomyopathy is the hallmark of hemochromatosis. The signal changes are the result of deposition of iron in the cardiac myocytes. Although myocardial signal may be diminished by amyloid deposition, blooming on gradient-recalled echo sequences is not a feature. Option D is not the best response.
Solution to Question 10
Regional thinning and fatty infiltration of the right ventricular myocardium is the characteristic MR feature of arrhythmogenic right ventricular dysplasia (ARVD). Cine MRI would show right ventricular dyskinesia. Option A is not the best response. Myocarditis is characterized by interstitial edema of the myocardium with myocyte necrosis. This pathology correlates with increased T2 signal intensity and focal delayed enhancement after gadolinium injection. The delayed enhancement represents active inflammation and irreversible myocyte damage [10]. Option B is the best response. In the setting of restrictive cardiomyopathy, multiple intramural nodules should suggest sarcoidosis rather than myocarditis. Although the appearance of sarcoid nodules may be variable on MRI, they typically show high T2 signal intensity and delayed enhancement. Option C is not the best response. Diffuse, concentric thickening of the atrial and ventricular walls, along with reduction in myocardial signal intensity on both T1- and T2-weighted imaging, in the setting of restrictive cardiomyopathy, is characteristic of cardiac amyloidosis. Option D is not the best response.
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