1352840 - Not All LV Hypertrophy Is HCM - That's #WhyCMR

Description of Clinical Presentation: In this case series, we emphasize the role of cardiac MRI in the evaluation of suspected hypertrophic cardiomyopathy (HCM) which may portend multiple differential diagnoses.

Diagnostic Techniques and Their Most Important Findings: Case 1 – 27-year-old male was referred to cardiac MRI for suspected HCM due to asymmetric LV septal hypertrophy seen on echocardiogram. Cardiac MRI showed a focal 30 x 15 mm thickening of the basal anterior and anteroseptal walls without extension into the myocardial fibers of the mid inferior septum, and with a prominent late gadolinium enhancement (LGE) pattern. This suggested an alternate diagnosis such as fibroma or sarcoma. A recommendation for myocardial biopsy was made based on this study. Pathology later showed this to be a fibroma.

Case 2 – 40-year-old female with nonischemic cardiomyopathy (LVEF 30-40%) and non-sustained VT was referred to cardiac MRI due to LV hypertrophy and focal RV free wall hypertrophy. Cardiac MRI showed asymmetric septal hypertrophy 20 mm in diameter, with a myocardial perfusion defect and LGE in the basal septum on the RV side. The LGE pattern did not fit HCM. Other differentials considered included cardiac sarcoid given the RV involvement, and her history of arrhythmia. She underwent right heart catheterization with biopsy of this region which was positive for cardiac sarcoidosis. Therapy was initiated and follow up PET/CT FDG myocardial scan showed minimal FDG uptake in the mid-basal septum with hypokinesis and a mild corresponding perfusion defect; likely representing resolving cardiac sarcoidosis given interval therapy.

Case 3 – 51-year-old male with palpitations and dizziness was evaluated by Holter monitoring and echocardiogram. The Holter monitor was unrevealing. Echo showed normal LV function with apical hypertrophy. Due to suspected apical hypertrophic cardiomyopathy, he was referred for cardiac MRI which showed a 40 mm mass in the distal septum with a perfusion defect and dense LGE in this area. This was thought to most likely reflect a fibroma, but other differentials including metastatic neoplasms could not be ruled out. It was decided to surgically excise the mass. A 45x26 mm mass was excised from the distal septum which was shown to be a fibroma on histology.

Learning Points from this Case: This case series emphasizes the additive diagnostic value of Cardiac MRI as a non-invasive imaging tool. Various underlying pathologies may initially present as variants of hypertrophic cardiomyopathy. Echocardiography is hampered by limited views and the inability to characterize tissue or assess for scar or inflammation. Cardiac MRI bridges that gap and should be considered as an important early step in the evaluation of LV hypertrophy.