CARDIOVASCULAR IMAGING: Coronary Arteries
Case Author: Eric Kimura-Hayama, MD, Instituto Nacional de Cardiologia Ignacio Chavez
History
65-year-old man with new onset of chest pain after surgical revascularization; CT angiography has been performed, and the next step must be determined.
Imaging Findings
Frontal (A) and left lateral (B) volume-rendered CT images show two left mediastinal vascular structures, one of which originates from the aorta (shown in a double oblique maximumintensity-projection image, C) and courses toward the left lateral wall of the heart. It has a nonuniform caliber and peripheral filling defects.
- Conventional angiography to assess size of aneurysm
- Follow-up CT angiography to assess rate of growth and patency of bypass graft aneurysm
- Medical management
- Surgical intervention to avoid rupture, fistula formation, embolization, and myocardial infarction
Diagnosis
Surgical intervention to avoid rupture, fistula formation, embolization, and myocardial infarction
Teaching Points
Aneurysms of vein grafts are rare and develop relatively late, on average 10 years after coronary artery bypass graft (CABG) surgery. The clinical presentation of vein graft aneurysms ranges from no symptoms with the incidental finding of a mediastinal or paracardiac mass on imaging to chest pain and myocardial infarction caused by thrombotic occlusion or distal emboli or mass effect on adjacent structures. However, most diagnoses of aneurysm and pseudoaneurysm are made as a result of a clinical event. As in other parts of the body, vein graft aneurysms are classified into true aneurysms and pseudoaneurysms. True aneurysms are composed of all three layers of the vessel wall, can be focal or diffuse, and involve any segment of the graft. They are secondary to atherosclerotic changes. Pseudoaneurysms are most commonly seen near anastomotic sites and can be the result of suture rupture due to tension at the graft anastomosis or of erroneous placement of a suture. They usually present soon after CABG surgery and are confined only by the adventitia, surrounding hematoma, or the pericardium. Contrast-enhanced CT is the best noninvasive imaging method for evaluating a mediastinal mass. It allows precise description of the extension, location, and morphologic characteristics of the aneurysm, such as the presence of thrombus and the size of the residual lumen. The true size and characteristics of the aneurysm are underestimated with invasive angiography because the images are lumenograms. However, because of the usual extensive calcification that necessitates CABG surgery, evaluation of native coronary arteries can be limited at CT. Because the rate of rupture of vein graft aneurysms appears to be high and associated with extensive morbidity and mortality, many centers recommend revascularization and surgical excision of large and patent vein graft aneurysms.
Suggested Readings
Frank L, Mueller GC, Attili AK. AJR teaching file: a right paracardiac mass in a patient with a history of coronary artery bypass grafting. AJR 2010; 195:S47–S49
Wigth JN Jr, Salem D, Vannan MA, et al. Asymptomatic large coronary artery saphenous vein bypass graft aneurysm: a case report and review of the literature. Am Heart J 1997; 133:454–460
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