Key points
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CT has emerged as an important imaging modality in the evaluation of cardiac and paracardiac neoplasms. CT has several advantages including wide availability, rapid acquisition time, excellent isotropic spatial resolution, and multiplanar reconstruction capabilities.
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CT is a robust technique for assessment of the relationship of the mass to the myocardium, cardiac valves, pericardium, coronary arteries, great vessels including pulmonary and systemic, and adjacent tissues, such as lung and lymph nodes, in a way that no other imaging modality can often reach.
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Cardiac CT possesses a fairly good capability for tissue characterization through assessment of the lesion density (distinguishing calcium and fat components from soft tissue). Cardiac CT is the best modality for determining calcification.
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Myxomas are the most common and lipomas are the second primary cardiac tumor in adults.
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The most common primary cardiac tumors in pediatric are rhabdomyoma and fibroma.
Tissue characterization
Primary benign cardiac neoplasms are more common than the primary malignant ones, most of them being myxomas. The CT features of the tumor that help distinguish benign from malignant neoplasms include location, size, margins, the presence of a feeding artery, calcification, or pericardial effusion ( Table 11.1 ).
Technical issues
The scan protocol used can vary given the variety of clinical scenarios that may precede referral to CT.
If possible, clinical history and any available prior imaging (echocardiography, prior CT of the chest, or PET scan) should be reviewed before CT imaging. Our routine protocol for most examinations on patients sent with cardiac mass is to obtain three-phase imaging (gated nonenhanced, coronary CT angiography phase, and 20-second delay phase).
Prospective ECG triggering is the default mode due to lower radiation exposure, but retrospective ECG gating is recommended if ventricular functional estimation, mass mobility, and valvular motion need to be evaluated. We use retrospective gating with tube current modulation and iterative reconstruction to reduce radiation dose .
If available, dual energy or perfusion techniques are selectively used to gain additional information about the mass characteristics or usefully display that information to referring clinicians. If the scan is to be combined with imaging of the chest or abdomen and pelvis, we generally scan the whole chest on the delay phase outlined previously and can obtain abdominal and pelvic phase imaging with the same contrast bolus on the portal venous phase, 70 s after contrast injection .
For cardiac masses, it is advantageous to use a triphasic injection protocol that enables visualization of all the cardiac chambers and reduction of streak artifacts in the SVC and right atrium. This involves initial contrast injection at a flow rate of 5–7 mL/s to opacify the left heart, followed by either a contrast injection at a slower rate of 2–4 mL/s or injection of a mixture of contrast and saline (50: 50 or 60:40 ratio) at the same flow rate of 5–7 mL/s to opacify the right heart and finally by saline bolus injection to minimize streak artifact .
Myxoma
Myxomas are the most common primary cardiac tumor in adults . They are benign lesions characterized by myxoid tissue and spindle cells, often arising along the left side of the interatrial septum, sometimes with a stalk. They are more common in women than men, by a nearly 2:1 ratio.6.
CT typically demonstrates a low-attenuation (usually water values for Hounsfield units) lobular mass with or without a stalk, usually attached to the left side of the atrial septum ( Figs. 11.2 and 11.3 ). Enhancement is typically absent or minimal. Calcification may be present in some cases .
Prospective ECG-gated cardiac CTA from a young male with syncope displays a huge mobile mass arising from the ventricular aspect of the mitral valve and protrudes into LVOT. A late image acquisition shows mild enhancement at some parts of the tumor.
Left upper extremity CT angiography reveals a filling defect at the distal part of the brachial artery. Due to critical limb ischemia, surgery was done for the patient, and metastatic myxoma was excised.
Lipoma
Lipoma is the second most common primary benign cardiac neoplasm (8%–12%) and most commonly occurs in middle-aged and older adults. Half of the cardiac lipomas originate from the subendocardial layer, and the other half arise from the subepicardial or myocardial layers and grow into the pericardial sac. Endocardial lipomas are small with a broad base of attachment and usually occur in the left ventricle or along the septal wall or roof of the right atrium.
On CT, lipomas are well defined, homogeneous, nonenhancing masses with fat attenuation (Hounsfield units less than − 50) located within the cardiac chamber ( Fig. 11.4 ), the myocardium, or in the pericardium. Large tumors can cause cavitary obstruction, compressive effects, and cardiac dysrhythmias .
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