Combined severe baffle obstruction and baffle leak, resulting in a significant right-to-left shunt in an adult with D-transposition of the great arteries after Mustard operation

Description of Clinical Presentation: Patient is a 55-year-old male with history of D-transposition of the great arteries. He underwent initial palliation with a Blalock-Hanlon atrial septostomy, followed by repair with a Mustard atrial switch operation at age 2. His baseline saturations have been in the mid to high 80s since early childhood, though no further investigation was performed as he remained active with few perceived limitations. Upon transfer to a new cardiologist, echocardiogram revealed a severely dilated and hypertrophied right ventricle with moderately decreased (systemic) systolic function, suspected mild systemic and pulmonary venous baffle obstruction (mean gradient 4-5mmHg), and mild aortic valve regurgitation, none of which explained the hypoxemia. Cardiac MRI was ordered to further evaluate the systemic and pulmonary venous baffles and assess sources of hypoxemia.

Diagnostic Techniques and Their Most Important Findings: Cardiac MRI was performed on a 1.5-T scanner. Cine SSFP images were acquired in the short axis, long axis, axial, and coronal planes. Phase contrast images were acquired for flow assessment. 3D MR angiogram was acquired after administration of intravenous gadolinium. MRA sequences showed complete obstruction of the superior limb of the systemic venous baffle with a large (18mm x 26mm) decompressing baffle leak into the right atrial appendage. SSFP cine sequences confirmed presence of the baffle leak and demonstrated severe right ventricular dilation with severely decreased right ventricular (systemic) systolic function (RV EF = 19%). Flow quantification in the main pulmonary artery and aorta confirmed a Qp:Qs of 0.83:1 (breath-held) to 0.90:1 (free-breathing).

Learning Points from this Case: Based on the findings from the cardiac MRI, the patient was referred for transcatheter treatment with the goal of improving his resting oxygen saturation and decreasing systemic right ventricular volume load. Angiography revealed obstruction of flow through the superior limb of the systemic venous baffle with flow of contrast via a fistula into the right atrial appendage and right atrium. The inferior limb of the systemic venous baffle had no obstruction. The patient underwent successful transcatheter recanalization of the superior limb of the baffle and covered stent placement to close the baffle leak. Room air oxygen saturation following the procedure was 95%. This case highlights the importance of cardiac MRI as an essential tool in guiding management for adult patients with complex congenital heart disease.

Figure 1: MR angiogram in the coronal (A) and sagittal (B) planes with 3D reconstruction (C), demonstrating obstruction of the superior limb of the systemic venous baffle with a decompressing baffle leak to the right atrial appendage.
Figure 2: Invasive angiograms from transcatheter stent placement in the superior limb of the systemic venous baffle. Initial contrast injection in the SVC in (A) AP and (B) lateral views demonstrates severe stenosis of the superior limb of the systemic venous baffle with baffle leak into right atrial appendage proximal to the obstruction. Repeat injection after intervention with multiple bare metal and covered stents in (C) AP and (D) lateral views demonstrates unobstructed flow through the superior baffle limb with no residual baffle leak.