Large Systemic Right Ventricular Outflow Tract Pseudoaneurysm in a Pediatric Patient with Hypoplastic Left Heart Syndrome and Extracardiac Fontan

Presenting Author(s)

• 

  Stephen C. Ream, MD

  Pediatric Cardiology Fellow
  SSM Health Cardinal Glennon Children's Hospital
  ST. LOUIS, Missouri, United States

Primary Author(s)

• 

  Stephen C. Ream, MD

  Pediatric Cardiology Fellow
  SSM Health Cardinal Glennon Children's Hospital
  ST. LOUIS, Missouri, United States

Co-Author(s)

• LS

  Laura Schoeneberg, MD

  Clinical Assistant Professor of Pediatrics
  Children's Mercy Kansas City
  Kansas City, Missouri, United States
• CR

  Chetana Reddy, MD

  Associate Professor
  SSM Health Cardinal Glennon Children's Hospital, United States
• WK

  Wilson King, MD

  Cardiologist
  SSM Health Cardinal Glennon Children's Hospital
  St Louis, Missouri, United States

Description of Clinical Presentation: A 5 year old male with a history of hypoplastic left heart syndrome had previously undergone staged palliation consisting of: 1. pulmonary artery (PA) banding with concomitant prostaglandin E1, 2. Norwood procedure with placement of a 5 mm Sano (right ventricle to pulmonary artery) shunt and removal of the PA bands, 3. Glenn shunt and Sano takedown, and 4. fenestrated extracardiac Fontan at 4 years of age. Following Fontan, a systemic right ventricular aneurysmal dilation was noted on routine echocardiography. The patient was asymptomatic and had no evidence of ventricular dysfunction or dysrhythmias. Cardiac MRI was performed to better characterize this finding and assist with interventional planning.

Diagnostic Techniques and Their Most Important Findings: The patient was scanned with a GE 3T 750W Discovery scanner with a 24 channel pediatric InkSpace coil. The following sequences were performed: Three plane localizer, Cine IR, IR FGRE 3D whole heart (1.2 mm), 4D flow (1.6 mm, Nex 5, Hyperkat 6, resp comp 20%, Acquired phases 20, Reconstructed phases: 25, Venc 160 cm/s time: 17:36), 3D cine (1.0 mm, Nex 5, Hyperkat 6, Acquired phases: 25, Reconstructed phases: 30, respiratory compensation: 20). 50 mg of ferumoxytol (2.96 mg/kg) was administered as a slow infusion over 15 minutes. The scan revealed a large right ventricular outflow tract pseudoaneurysm (30.6mm x 13.8 mm). The pseudoaneurysm wall was thin at 3.3 mm in comparison to the normal surrounding myocardium (5.5 - 7.7 mm) and exhibited paradoxical motion, expanding during systole and contracting during diastole. Additionally, 4D flow sequences demonstrated moderate left common carotid stenosis near a previously placed aortic arch stent. Retrospectively, the aneurysm was present at cardiac catheterization as early as post-operative day 81 following Sano shunt. The aneurysm had grown 2.9mm (10.4%) in length over the 16 months prior to MRI.

Learning Points from this Case: The pseudoaneurysm location was at the site of the previous Sano shunt. At least 1 other case of a similar aneurysm has been reported, with the etiology thought to be related to aggressive coring out of the infundibulotomy site and incomplete incorporation of myocardial layers when suturing the shunt (1). Due to the progressive enlargement of the pseudoaneurysm, the patient underwent surgical resection and patching with Dacron hemashield in an attempt to minimize future risks of myocardial dysfunction, dysrhythmia, and rupture. Post-operative echocardiography showed successful patch repair with normal systemic right ventricular function. At 1 month follow up post-repair, the patient had recovered well and remained asymptomatic. Cardiac MRI was critical in the accurate 3D anatomical characterization of the aneurysm as well as evaluating its dynamic properties, ultimately assisting in a safe and successful surgical repair. Of note, only whole heart acquisitions were performed, enabling efficient image acquisition.

Figure1. Streamline sequence showing vortical flow at the RVOT pseudoaneurysm
Figure 2. High resolution SPGR cine at (1.0 x 0.47 x 0.47 mm).
Figure 3. 3D reconstructions (A, C) of RVOT pseudoaneurysm and (B) sagittal slice from 3D reconstruction