CASE 11745 Published on 09.08.2014

Aneurysm of a right coronary artery bypass graft (CABG): Saphenous Vein Graft (SVG)

Section

Cardiovascular

Case Type

Clinical Cases

Authors

Amir Awwad, Yutaro Higashi, Lisa Hamilton, Maruti Kumaran

Nottingham Univ. Hospitals,
Queen's Medical Centre,
Radiology Department,
Derby Road, Nottingham;
Email:amirawwad@hotmail.com
Patient

77 years, male

Categories
Area of Interest Cardiac, Cardiovascular system, Vascular, Arteries / Aorta ; Imaging Technique MR, MR-Angiography, CT
Clinical History
Patient with a history of quadruple coronary artery bypass surgery (25 years before) and angina presented to the medical team with cough, fatigue and poor appetite. Blood tests showed anaemia and thrombocytopaenia. Clinical assessment prompted a chest radiograph and subsequent cross-sectional imaging.
Imaging Findings
Comparison with previous radiographs show an exaggerated, dense and unusual contour adjacent to the right heart border. An urgent arterial phase scan of the chest and abdomen was performed which demonstrated a 7.5 x 6.4 x 10.2 cm mass right on the right side of the heart with localized mass effect indenting the right atrium (RA), right ventricle (RV) and atrioventricular (AV) groove.
ECHO cardiogram showed akinesia of the mid-basal cardiac wall and the mass turned out to be a pseudo-aneurysm containing some thrombus. No significant valvular disease was identified.
A cardiac MRI (Single-shot and late Gadolinium) demonstrated an aneurysmal right coronary artery graft as a mass adjacent to right heart border and compressing RA. However, there was normal RV size and function. The left ventricle was not dilated with mild inferior hypokinesia but overall good systolic function (ejection-fraction = 58%). No obvious valvular regurgitation. No abnormal enhancement on delayed Gadolinium imaging.
Discussion
Background

Saphenous Vein Graft (SVG) aneurysm is a rare (0.1%) but serious complication presenting post-CABG with a time-interval varying from two weeks to 20 years [1-3, 5]. While a distinction between true and false aneurysms (pseudo-aneurysms) is crucial to better manage and predict their sequelae, differentiating between the two may not be immediately clear. Late-presenting aneurysms are commonly true-aneurysms diagnosed > 5 years post-surgery with subtle or no early warning symptoms. However, aneurysmal rupture leading to haemo-thorax/haemo-mediastinum has been reported previously [3].

Pseudo-aneurysms present early though late presentations have also been reported. They usually arise at vascular anastomoses sites [5]. Pathological mechanisms include imperfect surgical technique, suture defects and graft infection in early post-operative course.
Developed graft (venous) wall weakness and focal dilatation at branching or valve-sites tend to cause true aneurysms [5, 7].

Clinical Perspective

Most cases present with intermittent chest pain, angina, infarction and aneurysm rupture [5]. If occult, with no ECG changes or biochemical abnormalities, detection as an incidental finding on imaging is possible [7]. Imaging may reveal a mediastinal or retro-sternal mass. Chest radiographs triggered by breathlessness/dysphagia, however, have low sensitivity and specificity. In the presented case, the initial interpretation of the mass was that of a hiatus hernia. Depending on clinical correlation, further cross-sectional & functional-imaging (CT, Cardiac-MR/ECHO) are necessary for diagnosis along with assessment of size/content of aneurysm (thrombus) along with evaluating cardiac functions [5].

Imaging Perspective

Cardiac CT/MRI are ECG-gated techniques to define the morphological and anatomical relationships of SVG aneurysm in the mediastinum [2]. CT was first requested in our case, which showed, following multi-planar reconstruction, the relevant anatomy of the aneurysm. Cardiac-MRI’s role is to dynamically define the content and mass effect of SVG aneurysm (impairing cardiac functions) and to assess its rupture risk [5]. Gadolinium-administration showed no enhancement, a feature required to exclude cardiac malignancies and areas of myocardial infarction. Given the presentation time, size and presence of intraluminal thrombosis, this was suspected to be a true SVG aneurysm. No aneurysm-related complications were identified at imaging, therefore no intervention was necessary. However, it is suggested in the literature to plan for follow-up [2, 5].

Outcome

Reported complications of SVG aneurysms may include rupture (causing tamponade &/or haemothorax), distal embolisation, infarction and fistulation [5-6]. With an unpredictable follow-up course, surgical resection &/or ligation are recommended in certain cases [5, 7]. Alternatively, if re-canalisation is possible to restore perfusion and chamber viability, cardiac catheter-stenting +/- coil-embolisation are two other options to prevent future complications [4-5].
Differential Diagnosis List
Aneurysm of right-sided saphenous vein bypass graft (SVG)
Hiatus hernia
Mediastinal mass
Cardiac mass
Lung pathology
Final Diagnosis
Aneurysm of right-sided saphenous vein bypass graft (SVG)
Case information
URL: https://www.eurorad.org/case/11745
DOI: 10.1594/EURORAD/CASE.11745
ISSN: 1563-4086