A 42-year-old male was transferred from an outside hospital for a wide complex tachycardia and concern for left ventricular mass. His ECG is shown (Fig. 1) and was concerning for a rapid VT (around 220 beats per minute), given the width of the QRS complex and positive concordance throughout the precordial leads. He was started on Amiodarone and underwent synchronized cardioversion, but by report his rhythm degenerated into VF and he underwent CPR for 1 minute before his rhythm stabilized. He was switched to procainamide and admitted to the hospital. He underwent a TTE which illustrated a large basal to mid posterior wall mass (Fig. 2). He had a past medical history of potential Wolff-Parkinson-White (WPW) syndrome (following a wide complex arrhythmia at age 17, declined electrophysiologic study at that time). He also had a history of hypertension, hyperlipidemia, and type 1 diabetes on insulin.
The differential diagnosis was broad, and including benign (cardiac fibroma, rhabdomyoma, myxoma, hemangioma, or lipoma) or malignant/metastatic etiologies for his mass which could result in his VT. Additionally, an atrioventricular re-entrant tachycardia was considered, given his potential history of WPW, but his baseline ECG lacked delta waves and no pre-excitation was visualized on telemetry (Fig. 1). Outflow tract or bundle branch re-entrant tachycardias were also considered, but less likely given the morphology of the VT.
A cardiac MRI was obtained for further tissue characterization of the mass. It revealed a large, well circumscribed mass in the basal to mid lateral wall, which measured 5.2x5.1x3.8cm (Fig. 3). Left and right ventricular function was preserved. There was poor uptake on first pass perfusion, and tissue mapping showed low T1 and T2 values for the mass, relative to native myocardium (Fig. 4). An FDG-PET was obtained to evaluate for metabolic activity of the mass and any concurrent masses or metastases. It showed hypointense uptake of the mass relative to native myocardium (Fig. 5) and no significant extra-cardiac uptake. A CCT was also obtained which showed no significant coronary involvement and no coronary calcification or stenosis. Given the hypointense uptake of the mass, low T1 and T2 values and association with VT, a working diagnosis of an intramyocardial fibroma was made.
A repeat MRI was obtained to ensure the mass did not infiltrate the atrioventricular groove or interfere with the mitral valve apparatus or papillary muscles. The MRI did not illustrate any involvement of the atrioventricular grove or mitral apparatus and did not appear to enter the cavity of the left ventricle. Given the localization of the mass without involvement of surrounding critical structures, surgical resection was recommended. He underwent successful surgical resection of the mass with primary closure of the left ventricle over felt (Fig. 6), and pathology was consistent with an intramyocardial fibroma. He had no recurrent sustained ventricular arrhythmias while hospitalized and was discharged on amiodarone and had a 30-day monitor placed to monitor for recurrences.