Left Atrial Mass
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October 2014   

Dear SCCT Member:

 

As you know, the SCCT is the only professional medical membership organization dedicated to ensuring patient access to the appropriate use of cardiovascular CT. The SCCT Board of Directors thought that it would be beneficial to our members to create a Case of the Month series showcasing cardiac CTA in various clinical scenarios. this series will be spearheaded by the collective members of the SCCT FiRST committee. Please provide feedback or forward any questions to info@scct.org 

 

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 Multimodality Imaging of a Left Atrial Mass

Kim L. Sandler, MD (1), Murray J. Mazer, MD (1), Allison M. Wasserman, MD (2), Julian A. Noche Munoz, MD (3), Jennifer R. Williams, MD (1) 


1. Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN

2. Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN

3. Department of Internal Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN

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History
A 66-year-old female with past medical history significant for paroxysmal supraventricular tachycardia, asthma, Graves disease, and anxiety presented to an outside hospital with chest pain and worsening shortness of breath.   She reported shortness of breath that was progressive over a month, despite increased use of her rescue inhaler. This was accompanied by substernal chest pain that radiated to her left arm and neck.  History was also significant for fatigue, weight loss, abdominal distention, orthopnea and paroxysmal nocturnal dyspnea.  While admitted at an outside facility, she underwent evaluation including a cardiac MRI and PET/CT.  The patient was transferred to our institution in stable condition after imaging was obtained.  

Findings
Cardiac MRI performed at an outside hospital demonstrated a left atrial mass with extension into the pericardium and associated pericardial effusion.  The PET/CT demonstrated a large, intensely avid cardiac mass without additional foci of abnormal FDG uptake. (Figure 1)

Figure 1:  MRI demonstrating a large left atrial mass with extension into the pericardium and pericardial effusion.  Small bilateral pleural effusions are also demonstrated (A).  PET imaging is limited, but clearly demonstrates significant FDG uptake correlating with the left atrial mass (B).

Following transfer to our institution, the patient was further evaluated with gated cardiac CT angiography (CTA).  This helped to further characterize the mass as partially calcified and occupying the majority of the left atrium.  There was extension into the left posterolateral portion of the pericardial sac and exophytic extension in the region of the mitral valve.  The aortic valve was not involved.  Imaging of the pulmonary veins demonstrated occlusion of the left lower lobe pulmonary vein with compression and possible early invasion of the left upper lobe pulmonary vein.  Ejection fraction was calculated at 42%. (Figure 2)



Figure 2: CTA images demonstrating a large left atrial mass extending into the pericardial sac (A) with associated pericardial effusion and bilateral pleural effusions.  The left lower lobe pulmonary vein is occluded with early invasion versus compression of the left upper lobe pulmonary vein.  Color rendering (B) further illustrates the mass extending to the mitral valve without significant left ventricular involvement.

Imaging was most consistent with a primary cardiac tumor, suspected to represent sarcoma.  Metastatic disease was felt to be less likely, given the absence of additional foci of abnormal FDG uptake on PET/CT.  The patient underwent minimally invasive right anterior thoracotomy with biopsy of the left atrial mass and performance of a pericardial window.  Pathologic evaluation was consistent with high-grade sarcoma. (Figure 3)



Figure 3: Pathologic evaluation of the left atrial mass demonstrates abundant mitotic figures and occasional apoptoses amongst a background of spindle cells, consistent with high-grade sarcoma.

Discussion
Primary cardiac tumors are exceedingly rare, with an incidence of less than 0.03%, and greater than 75% of these are benign.(1) Nearly all primary malignant cardiac tumors are sarcomas.(2) Angiosarcoma is the most common pathologic subtype and typically involves the right atrium, while the less common undifferentiated sarcoma is more often seen in the left atrium.(3) Though patients may be asymptomatic until the disease reaches an advanced stage, they most often present with refractory heart failure, often with an associated pericardial effusion.(4)

Once detected, cardiac masses can be evaluated using a multitude of imaging modalities, including echocardiography, gated cardiac CTA, cardiac MRI, and even PET/CT as was performed in this case.  Gated cardiac CTA is particularly helpful in providing anatomic detail, assessing for the presence of calcifications, and for detecting vascular invasion.(5) While differentiation of benign from malignant cardiac tumors can be difficult, malignant features include size greater than 5 cm, associated pericardial effusion, broad-based attachment with ill-defined margins, and heterogeneous enhancement following contrast administration.

Commonly encountered benign lesions in the left atrium include atrial myxoma and thrombus.(1) Additionally, mass-like lipomatous hypertrophy of the interatrial septum can mimic a left atrial tumor, however fat within the lesion should be apparent on both CTA and MRI.  The prognosis for cardiac sarcoma is universally poor, with a mean survival of 9-11 months. Median survival ranges up to 24 months in patients who undergo complete resection, but remains 10 months following incomplete or no resection.(4)
References
1. Hoey ETD, Mankada K, Puppalaa S, Gopalan D, Sivananthanan MU. MRI and CT appearances of cardiac tumours in adults. Clinical Radiology. 2009;64:1214-30.

2. Tatli S, Lipton MJ. CT for intracardiac thrombi and tumors. The International Journal of Cardiovascular Imaging. 2005;21:115-31.

3. Araoz PA, Eklund HE, Welch tJ, Breen JF. CT and MR Imaging of Primary Cardiac Malignancies. Radiographics. 1999;19:1421-34.

4. Shanmugam G. Primary cardiac sarcoma. European Journal of Cardio-thoracic Surgery. 2006;29:925-32.

5. Buckley O, Madan R, Kwong R, Rybicki FJ, Hunsaker A. Cardiac Masses, Part 1: Imaging Strategies and Technical Considerations. AJR. 2011;197:837-41.

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