Elsevier

Clinical Radiology

Volume 60, Issue 6, June 2005, Pages 687-692
Clinical Radiology

Left ventricular aneurysm: comprehensive assessment of morphology, structure and thrombus using cardiovascular magnetic resonance

https://doi.org/10.1016/j.crad.2005.01.007Get rights and content

AIM

To demonstrate that cardiac magnetic resonance (CMR) techniques provide unique and definitive information on the presence, location, size and nature of left ventricular aneurysm and pseudoaneurysm, the presence of thrombus and the viability of myocardium.

METHOD

A retrospective study of 27 patients with a final diagnosis of left ventricular aneurysm or pseudoaneurysm, who underwent CMR at a tertiary referral centre in the period between 2000 and 2003.

RESULTS

In 7 cases the correct diagnosis of true aneurysm was confirmed; in 7 cases previously unsuspected thrombus was identified; in 7 cases an unsuspected pseudoaneurysm was identified; and in a further 6 cases a previously unsuspected aneurysm was identified.

CONCLUSION

CMR refined the diagnosis in the majority of patients with left ventricular aneurysm, and should be considered in all cases of confirmed or suspected left ventricular aneurysm.

Introduction

The formation of a left ventricular aneurysm or pseudoaneurysm occurs most commonly secondary to myocardial infarction.1, 2

A true left ventricular aneurysm is an out pouching of the infarcted left ventricular myocardium which moves dyskinetically in systole. The key feature of a true aneurysm is that its wall consists of continuous myocardium. Abnormal flow in the aneurysmal sac predisposes to thrombus formation which carries a risk of thromboembolism. Once identified, a true left ventricular aneurysm may either be treated medically (with anticoagulation and treatment for heart failure, as appropriate) or surgically if there are haemodynamic consequences, intractable heart failure or ventricular dysrhythmias.

False left ventricular aneurysm is a result of rupture of the left ventricular free wall. In many cases cardiac tamponade follows swiftly and is a cause of sudden death in the first few days following myocardial infarction. In some cases, however, the pericardium contains the rupture locally and a sac is formed bounded by pericardium and inflammatory tissue, causing false aneurysm formation.3

The presence of an aneurysm predisposes to heart failure, arrhythmias and thrombus formation. True and false aneurysms are managed differently, because of the risk of rupture in the case of false aneurysm. This risk is perceived to be high, and consequently identification of a pseudoaneurysm is important and generally indicates surgical repair.4

The diagnosis of left ventricular pseudoaneurysm is a challenge. Imaging features that help to differentiate false from true aneurysms include the neck-to-body diameter ratio (smaller in false aneurysm);5 distribution of the aneurysmal sac; and discontinuity of myocardium at the neck of the aneurysm. These features are most frequent in the inferior left ventricular wall which may, however, be difficult to demonstrate with echo techniques.6 Coronary angiography may distinguish pseudoaneurysms by the absence of coronary arteries near the affected territory.7

Thrombus formation is a common complication of a true left ventricular aneurysm.8 Clot presents a systemic embolic risk, and it is common clinical practice to institute anticoagulation to reduce this risk once identified. In a false aneurysm, thrombus formation is part of the process which contains the ventricular rupture so, at least acutely, anticoagulation is contraindicated.9 It is therefore important to identify the presence of thrombus as well as to differentiate true from false aneurysm, as a guide to whether anticoagulation should be instituted.

If surgical repair is being contemplated for either true or false aneurysm, the identification of viable myocardium is important. Using the technique of late enhancement CMR following intravenous gadolinium administration, areas of myocardium can be identified which are unlikely to improve function following revascularization, in addition to areas of transmural infarction.10 This information allows the cardiac surgeon optimally to plan the procedure.

The presence of left ventricular aneurysm may be established by a number of other methods. Persistent ST segment elevation on electrocardiography has a low sensitivity and specificity for the presence of aneurysm. Echocardiography provides comprehensive assessment of structure and function. Left ventricular opacification by transpulmonary bubble contrast agents allows a clearer endocardial definition.11 However, this is often hampered by, for example, suboptimal echo windows or the limited number of imaging planes available. Aneurysm formation occurs most commonly on the inferior aspect of the left ventricle, where it is more difficult to demonstrate using echocardiography. Transoesophageal echo often has better image quality, but is semi-invasive and does not show the apical regions of the left ventricle easily.12 The presence of a true or false left ventricular aneurysm is usually obvious on left ventriculography. This, however, is an invasive procedure requiring a catheter to be manipulated in the left ventricular cavity, and carries an associated risk.

There have been many advances in CMR over recent years. CMR presents a comprehensive assessment of the morphology of the aneurysm and adjacent myocardium. Tissue characterization by CMR provides additional important information not available with other techniques. An additional benefit of CMR is that it does not involve exposure to ionizing radiation.

Section snippets

Patient characteristics

Patients were identified by searching the database of our tertiary CMR centre for individuals with a final diagnosis of left ventricular aneurysm or pseudoaneurysm, in the period between 2000 and 2003. All such patients were included and had all undergone routine investigations, including echocardiography, before referral for CMR imaging. The clinical details were collated from the clinical case notes, referral letters and our records from the time of radiography. Ethical approval was not

Results

Table 2 presents the final diagnoses following CMR imaging. In all, 7 cases were referred with the correct diagnosis of true LV aneurysm; 7 had intracardiac thrombus not apparent on echocardiography; and 7 were shown to have a false aneurysm which had not been identified before the CMR, including 3 cases where an aneurysm was not suspected. A further 6 patients who underwent imaging for unrelated reasons were found to have a true left ventricular aneurysm. The diagnosis of pseudoaneurysm was

Discussion

The most recent review in the literature of the diagnostic yield of various imaging techniques for left ventricular aneurysm was in 1997. This reported a retrospective series identified from a literature search of 290 patients with a final diagnosis of pseudoaneurysm, in the period between 1966 and 1997.16 During this time, invasive angiography was the most sensitive method of establishing the diagnosis in 172 of 197 cases, and m-mode echocardiography was the least effective, identifying a

Conclusions

Contemporary CMR techniques provide a comprehensive assessment of the presence and nature of left ventricular aneurysms without involving exposure to ionizing radiation.

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