A marble in the heart: CMR for the diagnosis of a rare intracardiac mass

Description of Clinical Presentation: A 76-year-old male patient with a history of hypertension, chronic kidney disease due to hypertensive nephrosclerosis, gout, and hypothyroidism undergoing evaluation for knee replacement underwent regadenoson Single Photon Emission Computed Tomography Myocardial Perfusion Imaging due to intermittent exertional dyspnea. This did not demonstrate any evidence of ischemia but noted a left ventricular ejection fraction of 46%. He underwent a transthoracic echocardiogram which demonstrated a left ventricular ejection fraction of 50-55% with moderate asymmetric left ventricular hypertrophy and a hyperechoic mass in the septal basal segments measuring 2.2 x 1.9 cm. He underwent Cardiac Magnetic Resonance (CMR) imaging for further evaluation. This demonstrated signal characteristics consistent with calcification, supportive of a diagnosis of idiopathic cardiac osseus metaplasia. He additionally underwent Position Emission Tomography to evaluate for intramyocardial inflammation, which was negative but did demonstrate a small, severe perfusion defect in the basal septal wall, consistent with the previously reported mass. He also underwent coronary angiography which was negative for epicardial coronary artery disease.

Diagnostic Techniques and Their Most Important Findings: CMR demonstrated a well-circumscribed, circular, and isointense mass within the basal anteroseptal segment, measuring 1.5 cm in diameter, on steady-state free precession (SSFP) imaging. The native T1 of the mass was significantly reduced at 363 msec. This mass was hypointense on T2 weighted turbo spin echo (TSE) imaging, demonstrated no uptake on first pass perfusion imaging, and no signal intensity on early or late gadolinium enhancement (EGE or LGE) imaging. These signal characteristics were most consistent with intramyocardial calcification.

Learning Points from this Case: This case showcases the ability of CMR to non-invasively and accurately characterize intramyocardial masses. We present a case of idiopathic osseus metaplasia which is a rare condition with a natural history that has been infrequently described. CMR provides both diagnostic and prognostic information which helps dictate optimal patient management of this rare entity, avoiding invasive biopsies or surgical resection. While prognosis has been reported to be poor in this condition due to the development of heart failure and conduction system disease, CMR is the optimal imaging modality to diagnose and serially monitor for any interval changes, in addition to enhancing our clinical understanding of such rare diseases.

Collage demonstrating the tissue signal characteristics of the myocardial mass on SSFP, T2 TSE, native T1, first-pass perfusion, EGE, and LGE sequences.