Oral Case
Abdulmajeed Alruwaili, MD
Pediatric Cardiology MRI fellow
Children's Hospital of Philadephia
Kevin K. Whitehead, MD, PhD
Cardiologist
Children's Hospital of Philadelphia
Danish Vaiyani, MD
Cardiologist
Children's Hospital of Philadelphia
David M. Biko, MD, MBA, FSCMR, FAHA
Chief, Body imaging
Children's Hospital of Philadelphia
Sara Partington, MD
CARDIOLOGIST
CHILDREN'S HOSPITAL OF PHILADEPHIA
Mark A. Fogel, MD, FACC, FAHA, MSCMR, FNASCI, FAAP
Professor
University of Pennsylvania
Matthew A. Harris, MD
Associate Director, Cardiac MRI
Children's Hospital of Philadelphia
Allen Kelleman, MD
MD
Children's Hospital of Philadelphia
A 5-month-old infant was evaluated for a cardiac murmur and desaturations. Based on echocardiography there was sub-pulmonary and pulmonary valve stenosis that was not amenable for catheter-based intervention. At surgery a mass in the right ventricle outflow tract (RVOT) causing RVOT obstruction was identified and observed infiltrating the right atrioventricular (AV) groove encompassing the right coronary artery (RCA). Given the ambiguity of the diagnosis and difficulty with resection, the surgeon biopsied the mass and performed a RV to PA conduit bypassing the obstruction. The patient was referred to cardiac MRI for further anatomic and tissue characterization. The regional biopsy was consistent with myofibroma.
Diagnostic Techniques and Their Most Important Findings: MRI on 1.5T delineated a cardiac mass on the anterior surface of the RV, extending to the RVOT cavity causing significant obstruction. The mass measured 1.8x1.5x1.2 cm. T1-weighted imaging, raised concern for involvement of the proximal right coronary. On tissue characterization of the mass, compared to remote myocardium, the mass appeared uniformly isointense on T1-weighted imaging and hyperintense on T2-weighted imaging. There was no obvious first pass perfusion, or delayed enhancement (DE) on traditional bright-blood technique viability imaging. The tumor MRI characteristics suggested a benign mass despite its invasive nature and provided the differential diagnosis of rhabdomyoma or myxoma. Fibroma seemed unlikely given the absence of DE. The patient returned for follow-up CMR at which time both traditional bright and dark blood viability techniques were performed. Only the dark blood technique clearly delineated the extent of the mass by demonstrating the DE within the RV cavity and along the RVOT. The blood pool obscured the DE using bright blood technique. The patient ultimately underwent cardiac mass excision, right ventricular outflow tract muscle bundle resection, pulmonary valve replacement, tricuspid valvuloplasty and revascularization of the right coronary artery with an internal mammary graft.
Learning Points from this Case:
This case represents an unusual presentation for myofibroma with failure of initial echocardiographic study to demonstrate the cardiac mass as well as coronary involvement. MRI could demonstrate the mass but could not identify fibrosis or the full extent of DE using traditional bright-blood technique since the bright signal from the blood pool obscured the bright signal of the DE. This study underscores the importance of using dark blood technique for characterization of cardiac masses adjacent to blood pool as well as using this technique to identify fibrosis within the RV cavity where trabeculae and masses are surrounded by blood pool signal.
Figure A. Long-axis view of the RV. Traditional bright-blood technique DE does not clearly identify DE. There are multiple regions of signal inhomogeneities within the RV cavity (arrows).
Figure B. In the same view as Figure A, dark blood viability clearly identifies and delineates the extent of the delayed enhancement thereby correctly confirming the surgical biopsy results. 
