Large Mitral Annular Left Ventricular Pseudoaneurysm Detected by Cardiac Magnetic Resonance Imaging

Case Report. A 57-year-old white female school teacher had undergone mitral valve replacement 8 months earlier for streptococcal endocarditis and had required subsequent repair of a paravalvular leak 2 months later. The patient recently fell and fractured her right tibia bone and presented to the clinic for preoperative cardiac evaluation and clearance prior to orthopedic surgery. The patient denied chest discomfort or shortness of breath and reported mild intermittent palpitations without syncope or near-syncope. On physical exam, her blood pressure was 78/54 mmHg and her heart rate was 92 beats/minute and regular. The patient’s jugular venous pressure appeared normal and her chest was clear. The left ventricular apex impulse was diffuse on palpation. Heart sounds were distant and a 2/6 soft systolic murmur was best heard at the left ventricular apex. The electrocardiogram (ECG) showed nonspecific ST-segment changes and the chest X-ray revealed cardiomegaly. A tranesophageal echocardiogram (TEE) was performed which demonstrated mild mitral regurgitation, a left ventricular ejection fraction of 45% and a narrow-neck large pseudoaneurysm involving the base of the inferior and posterolateral left ventricular walls. Flow was present in the cavity of the pseudoaneurysm. A cardiac magnetic resonance image was performed using the 1.5 Tesla Philips Impera scanner (Philips Medical Systems, Andover, Massachusetts) with balance fast-field echo sequence, which confirmed the presence of a large posterior pseudoaneurysm measuring 70 mm x 50 mm. (Figures 1 and 2). At surgical exploration, dehiscence in the submitral valve area was observed along the entire posterior annulus. The patient underwent successful repair of the left ventricular pseudoaneurysm and was discharged from the hospital 1 week later in stable condition. Discussion. LVPA is the result of cardiac wall rupture contained by overlying adherent pericardium or scar tissue.¹ The common etiologies of LVPA are myocardial infarction (inferior infarct is most common), cardiac surgery (especially mitral valve repair²), trauma or infection.³ The most frequent symptoms of LVPA are related to congestive heart failure and include dyspnea or chest discomfort, but as was observed in the present case, up to 10% or more of patients can be asymptomatic.^3,4 Complications related to LVPA include rupture, congestive heart failure, thromboembolism and arrhythmias. The physical exam may demonstrate a new murmur and the ECG is usually nonspecific. The chest X-ray usually shows an enlarged heart. Transthoracic echocardiography (TTE) and TEE are useful first steps in establishing the diagnosis,⁵ and left ventriculography may be done for confirmation.⁶ Although echocardiography and contrast ventriculography may be useful in the evaluation of LVPA, the echocardiogram has field-of-view limitations, while angiography is invasive and has the potential for thrombus dislodgement. Cardiac MRI has emerged as a useful technique for diagnosing suspected LVPA.^7–9 A characteristic MRI feature of LVPA is the presence of markedly delayed enhancement of the pericardium which may be used to differentiate LVPA from a true aneurysm.⁷ Cine MRI also has the capacity to demonstrate blood-flow turbulence in the cardiac chambers, which is a hemodynamic feature of LVPA.⁸ As posterior and inferior left ventricular locations are most common for LVPA,^4,7 the tomographic format of MRI provides improved spatial resolution in comparison with TTE. As left ventricular mural thrombus is common in LVPA, Cardiac MRI may be superior to TEE for the detection of thrombi as well.¹⁰ Due to the risk of rupture, prompt surgical resection and repair of LVPA is the treatment of choice. In the present case, cardiac MRI contributed to the expeditious and definitive preoperative diagnosis of LVPA, and should be considered in the workup of patients in whom LVPA is a possibility.

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