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CASE OF THE MONTH

January 2011

Pseudoaneurysm of the Mitral-Aortic Intervalvular Fibrosa:

A Delayed Complication of Aortic Root Replacement

Entrikin DW, Shroff GS, Kon ND, Carr JJ

Wake Forest University School of Medicine

History

A 41 year old male with history of endocarditis underwent aortic root replacement with a cryopreserved aortic allograft. 16 months later transthoracic echocardiography (TTE) revealed moderate aortic insufficiency, distortion of the aortic root and left ventricular outflow tract (LVOT), and suggested a possible fistula from the aortic root to left atrium (LA). He was referred to our institution for possible redo aortic root replacement. A preoperative cardiac CT was performed to assess for coronary artery disease and to further evaluate this complex anatomy.

Cardiac CT & Operative Findings

Cardiac CT revealed no evidence of coronary artery disease, but clearly delineated a large pulsatile pseudoaneurysm of the mitral-aortic intervalvular fibrosa (MAIVF) originating immediately below the noncoronary cusp of the aortic valve (figures 1-3). Intraoperative transesophageal echocardiography (TEE) confirmed these findings (figures 1-2). Operative exploration demonstrated a large pseudoaneurysm extending posteriorly/superiorly from the LVOT towards the dome of the left atrium originating from a narrow neck that was a defect in the MAIVF. The allograft was removed, the annulus debrided, the pseudoaneurysm of the MAIVF excluded and allowed to drain into the pericardial space, and a freestyle porcine aortic root bioprosthesis was placed.

Figure 1: Oblique multiplanar reformatted (MPR) image (a) and TEE (b) image through the LVOT during systole demonstrating a narrow-necked pseudoaneurysm (PSA) of the MAIVF disrupting the fibrous continuity between the aortic and mitral valves (arrows). Corresponding diastolic images in (c) & (d) demonstrate decompression of the pseudoaneurysm into the LVOT. (LA - left atrium; Ao - aorta)

2011 Jan figure 2
Figure 2: Oblique MPR (a) and TEE (b) images oriented transversely through the LVOT during systole demonstrated the neck of the pseudoaneurysm as a discontinuity in the MAIVF closest to the septal portion of the LVOT (asterisks). Corresponding diastolic images in (c) & (d) demonstrate decompression of the pseudoaneurysm into the LVOT.

Discussion
The thin band of fibrous continuity between the aortic and mitral valves is the MAIVF. Pseudoaneurysms of the MAIVF are rare, typically occurring in the setting of aortic valve replacement or as a complication of infectious endocarditis, although more rarely can be congenital or seen as a complication of chest trauma ¹. Potential complications include rupture into pericardium with tamponade, LVOT-LA fistula, and symptomatic coronary artery compression^2-4.

2011 Jan figure 3

Figure 3: Systolic phase three-chamber MPR (a) demonstrating a large defect in the MAIVF, with a fully expanded pseudoaneurysm (PSA) extending posteriorly from the LVOT. Oblique thick-slab blood pool inversion 3D volume rendered image (b) through LVOT, aortic root and ascending aorta (Ao). The curved white lines demonstrate the region of the MAIVF, extending from the aortic root to the mitral annulus immediately above the anterior leaflet of the mitral valve (MV-A). Note the large defect in the MAIVF immediately adjacent to the septal portion of the LVOT (arrow).

References

1. Borges A. False aneurysm of the mitral-aortic intervalvular fibrosa after uncomplicated aortic valve replacement. Journal of the American Society of Echocardiography 2002;15:743-5.

2. Qizilbash AH, Schwartz CJ. False aneurysm of left ventricle due to perforation of mitral-aortic intervalvular fibrosa with rupture and cardiac tamponade: Rare complication of infective endocarditis. The American Journal of Cardiology 1973;32:110-3.

3. Bansal RC, Graham BM, Jutzy KR, Shakudo M, Shah PM. Left ventricular outflow tract to left atrial communication secondary to rupture of mitral-aortic intervalvular fibrosa in infective endocarditis: Diagnosis by transesophageal echocardiography and color flow imaging. Journal of the American College of Cardiology 1990;15:499-504.

4. Kim HW, Chung CH. Mitral-aortic intervalvular fibrosa pseudoaneurysm resulting in the displacement of the left main coronary artery after aortic valve replacement. The Journal of Thoracic and Cardiovascular Surgery 2010;139:e18-e20.