Case Author(s): Eric Hutchins, M.D. and Tom R. Miller, M.D., Ph.D. , 10/1/04 . Rating: #D3, #Q5

Diagnosis: Aortic Pseudoaneurysm

Brief history:

62 year-old woman with known coronary artery disease (CABG four years ago) presents to the emergency department with chest pain.

Images:

Raw projection data from a myocardial perfusion scintigraphy performed with Tc-99m sestamibi (L LAT-LAO-RAO)

View avi cine image (2 meg)

View main image(mi) in a separate image viewer

View second image(mi). Slice display from SPECT myocardial perfusion scintigraphy

View third image(mi). ECG-gated display from SPECT myocardial perfusion scintigraphy

Full history/Diagnosis is available below

Diagnosis: Aortic Pseudoaneurysm

Full history:

62-year old woman with known coronary artery disease who underwent 2-vessel coronary-bypass grafting 4 years ago, now admitted from the emergency department with a 3-4 day history of chest pain exacerbated by swallowing.

Radiopharmaceutical:

2.5 mCi Tl-201 chloride i.v. and 21.2 mCi Tc-99m sestamibi i.v.

Findings:

The projection images demonstrate a focal area of decreased activity within the mediastinum just superior to the heart.

The slice display shows a large, moderately reversible perfusion defect of mild severity in the lateral wall indicating a mixed lesion of infarction and ischemia. There is also a moderate-sized, nonreversible perfusion defect of moderate severity in the anteroapical wall due to infarction.

The ECG-gated images demonstrates moderate to marked left ventricular enlargement and a left ventricular ejection fraction of 33%.

Discussion:

The photopenic structure in the mediastinum could represent a relatively hypovascular mass. Alternatively, it could be a blood-containing structure because the activity of Tc-99m sestamibi in the blood is minimal at the time of cardiac imaging.

This is an obvious abnormality only if you look at the projection images. It is preferable to begin evaluation of myocardial perfusion images with the cine display of these images, typically to assess for motion or prominent liver or bowel uptake, although as in this case other important abnormalities may only be seen in this format.

Followup:

The patient went for an emergency CT which showed a 6.8 x 6.5 x 9 cm enhancing structure containing eccentric thrombus most consistent with an aortic pseudoaneurysm from the patient's previous aortotomy site.

At subsequent cardiac catheterization, the pseudoaneurysm was found to be superior to and not involving the coronary arteries or the bypass grafts. Also, the left anterior descending artery was occluded after small septal and diagonal branches. The left internal mammary artery to LAD graft was patent but the distal LAD was thread-like and small with marked diffuse plaque. The circumflex coronary artery was small and diffusely diseased. The radial artery graft to several distal circumflex vessels was without significant lesion.

Surgical repair confirmed there was no involvement of the coronary arteries or bypass grafts by the pseudoaneurysm.

View followup image(ct). CT images of the thorax

Major teaching point(s):

Evaluation of myocardial perfusion images should begin with the cine display of the projection data where important findings are sometimes made.

Differential Diagnosis List

A blood-containing structure or any relatively avascular structure in the mediastinum, including hematoma, cyst, abscess, necrotic tumor, etc.

ACR Codes and Keywords:

References and General Discussion of Myocardial Imaging (Anatomic field:Heart and Great Vessels, Category:Effect of Trauma)

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Case number: mi029

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