1355614 - Role of cardiac MRI in diagnosis of contained left ventricular rupture and differentiating it from true aneurysm.

Left ventricular wall rupture is a rare but serious complication of acute myocardial infarction (1). The rupture can rarely be contained by pericardium, fibrous tissue and thrombus forming a pseudoaneurysm(2). 

86-year-old male with no known prior co-morbidities presents with acute chest pain, dyspnea and features of heart failure. ECG showed sinus rhythm and minimal ST elevation in anterior leads; myocardial infarction suspected. PCI of RCA moderately narrowed was done and LCx which was occluded. He clinically improved and echocardiogram was scheduled. ECHO showed inferolateral pseudoaneurysm with thrombus just below the mitral valve apparatus, EF 25-30%. Cardiac MRI was ordered to confirm ECHO findings. Patient was discussed in the cardiothoracic multi-disciplinary meeting for possible surgical intervention. Due to his age, he was considered a poor candidate for surgical intervention and discharged home on medical therapy. Patient passed on 6 months later.

Diagnostic Techniques and Their Most Important Findings:

Cardiac MRI was done in a 3T scanner with pre and post contrast images obtained. Balanced Turbo Field Echo-Breath Hold (BTFE-BH) four chamber and short axis cine loops showed global LV hypokinesia with basal dyskinetic motion and basal inferior and inferolateral wall akinesia. Wide-necked (measuring 2 cm) 'aneurysmal' sac of the basal inferior and inferolateral LV wall was seen with the aneurysmal sac diameter of 3 cm. The aneurysmal wall appeared thick when compared to the rest of the myocardium mimicking a true aneurysm with all three layers. However, on closer look and adjusting the window level of the BTFE-BH images it was noted that the aneurysmal sac wall had a higher signal than the rest of the myocardium. Delayed post contrast images (PSIR-TFE-BH), 10 minutes after Gadolinium contrast administration demonstrated signal drop out within the ‘aneurysmal wall’ in keeping thrombus with marked delayed enhancement of the pericardium. These findings were in keeping with LV basal inferior and inferolateral wall pseudoaneurysm where the thrombus and the enhancing pericardium were containing the LV contents. No pericardial fluid or hemopericardium. Reduced LVEF; 18%. RVEF 42%.

Learning Points from this Case:

<1Although the appearances mimicked those of a true aneurysm the following features supported this this to be a pseudoaneurysm.  
1. Location of aneurysm: Contained rupture mostly involves the posterior wall followed by lateral wall (4). True aneurysms are mostly anterior or apical.  
2. Thrombus and enhancing pericardium: These are pathognomonic for contained LV rupture.
3. Slightly increased wall thickness compared to the rest of the myocardium and increased signal are unlikely in true aneurysm and were suggestive of thrombus. This is useful in cases where contrast cannot be administered.
4. Low ratio of maximal internal width of the orifice to maximal parallel internal diameter of the pseudoaneurysm 0.6 (< 0.9) (4,5).