Teaching Case

A diabetic patient with history of myocardial infarction, 8 years before treated with PTCA and stenting of the right coronary artery, needed pre-surgery chest X-ray for ophtalmologic surgery (proliferative haemorragic retinopathy). In general he appeared to be in good health.

Chest X-ray showed middle mediastinal mass, with positive "silhouette sign" with the left heart wall, not identifiable in a chest X-ray performed 9 years before (Fig. 1a, b and 2a, b). The differential diagnosis for this finding comprises: aneurysm or pseudo-aneurysm of left ventricle, pericardial cyst or lung disproliferative lesion.
A thorax CT-scan with iodine contrast media was requested to clarify the pertinence of the mass.
CT scan revealed a wide aneurysmatic dilatation of postero-lateral wall of the left ventricle (8x5 cm) at mid-basal level (Fig. 3a and b), associated with large endocavitary thrombus and a thin wall with focal small calcifications (Fig. 4a and b), that correspondend to the mediastinal mass seen at chest X-ray.
Transthoracic echocardiography confirmed the findings and demonstrates mitral valve regurgitation and akinesia of the infero-posterior segments. Coronary angiography found restenosis of the right coronary artery and a sub-stenosis of the proximal part of the left anterior interventricular artery.

Left ventricular aneurysm and pseudo-aneurysm are two severe complications of myocardial infarction, since they can manifest with sudden cardiac death (23% [1]) or lead to congestive heart failure, embolic events and ventricular arrhythmias. Differentiation of these two pathologies can be difficult, since pseudo-aneurysm is contained only by an adherent pericardium [1].
Left ventricular aneurysm is a dilatation of the ventricle with fibrotic wall that results from healed transmural myocardial infarction. The involved wall is either akinetik or dyskinetik during systole [2].
Left ventricular aneurysms occur in 8% of patients with previous history of myocardial infarction [3], of which the majority are found at the apical level and only 3% are at posterior or inferior wall level [1]. Anterior wall aneurysms are often more fatal than posterior ones, which by the way can involve papillary muscles and cause severe valve regurgitation. The more posterior the aneurysm is, the more difficult is its detection [1]. Left ventricular aneurysms are often asymptomatic and discovered incidentally; they have a low rate of rupture (7%) and are often treated with medical therapy or elective surgery [1].
Pseudo-aneurysms occur after a rupture in the free left ventricle wall and are contained by the overlying pericardium; they have higher chance of rupture (30-45% [4]) and require urgent surgical resection.
At transthoracic echocardiography almost 80% of people with pseudo-aneurysm, unlike patients with aneurysm, have a orifice-to-pseudoaneurysm diameter ratio < 0,5 [4].
CT and MRI can help in making differential diagnosis [5-6]: CT-scan can show the narrow neck of the pseudo-aneurysm and the endocavitary thrombus, if present; MRI with late gadolinium enhancement can show the myocardial fibrosis and the characteristics of the ventricular wall. Also with cine-cardiac MRI is possibile to evaluate the heart contractility.
Angiography of the left ventricle remains the most reliable method for diagnosis [4], since, in case of a pseudoaneurysm, the narrow neck connecting the ventricle to the cavity permits the contrast liquid to remain for several beats after injection into the ventricle cavity.
In some cases, like the one reported, surgical exploration is necessary to have a clear and certain diagnosis and, if needed, taking a histological sample to be analysed.
Our patient underwent double coronary bypass and the aneurysmectomy of the left ventricle via medial sternotomy, confirming a large aneurysm of the postero-lateral wall (Fig. 5 a, b). The aneurysm consisted of a very thin myocardium layer with overlying thrombus of about 5.5 x 2.5 cm.