1356822 - Multimodality Imaging Assessment of Mustard Venous Baffle Obstruction

A 20-year-old female patient with clinical history of  dextrocardia, {S,L,L} with pulmonary atresia status post Mustard atrial switch and Rastelli conduit repair, with MR conditional ICD presented with increasing fatigue and exercise intolerance. A recent CT Angiogram performed at a separate institution demonstrated concern for pulmonary baffle obstruction. Cardiac magnetic resonance (CMR) imaging was performed to evaluate function and volumes and assess candidacy for intervention. The referring cardiologists also requested a 3D model of patient anatomy to assess pulmonary venous and inferior baffle obstruction.

Diagnostic Techniques and Their Most Important Findings:

CMR was performed on a 1.5T Siemens Aera scanner (Siemens, Erlangen, Germany) with ferumoxytol enhancement. CMR data included MR Angiography and 4D Flow (48 slices, 77 x 160 matrix, Flip Angle 15°, TE/TR= 2.19/56.8, 3 segments, 2.5 mm isotropic voxel size). Clinically significant findings included moderate pulmonary venous baffle obstruction with narrowing down to 12 mm entrance at the level of the septum primum and flow acceleration (Figure 1). Additionally, the inferior systemic venous limb narrowed to 7 mm in the intracardiac portion inferior to pulmonary venous baffle obstruction. There was moderate conduit stenosis with no significant flow maldistribution. There were no baffle leaks visualized, and the measured Qp:Qs was 1:1. There was normal biventricular size and function. There was overall good visualization of cardiac structures despite the presence of metal artifact from ICD lead in the right ventricle.

A 3D model of the heart was segmented in Mimics (Materialize, Leuven, Belgium). The pulmonary veins, left atrium, left ventricle and aorta were primarily segmented from CT angiogram, however the systemic venous return lacked sufficient contrast to readily identify inferior systemic venous limb stenosis; the CMR MR angiography was segmented, followed by alignment of the respective masks. A 3D shell of the heart was segmented, and portions of the ventricles were removed for visualization of the interior structures of the heart. The entry points of the systemic venous baffles , and orifice of the stenotic pulmonary venous baffle were identified and delineated with 3D rings (Figure 2). After reviewing 4D flow data and 3D models, the patient underwent right and left heart catheterization which confirmed the regions of obstruction.

Learning Points from this Case:

Patients who have undergone Mustard atrial switch operations are at risk for stenosis/leaks in the systemic and pulmonary venous baffles. 4D flow CMR can also readily identify these regions, although  comprehensive anatomic delineation of these regions (with 3D printing) may require multimodality imaging, including both CT and CMR.