Is that a post ablation thrombus?...Well, it could be calcium (QF_TH_065)

A 56 year old male with double-outlet right ventricle (DORV) and normally related great arteries status-post complete repair was admitted for an episode of left sided ventricular tachycardia (VT). Additional surgical history is notable for a Konno procedure with mechanical aortic valve replacement (AVR), ventricular septal defect (VSD) patch revision, and tricuspid valve ring annuloplasty. He had a successful electrophysiologic study (EPS) with VT pathway ablation. He was referred for cardiac MRI (CMR) prior to assess his ventricular size and function, valve regurgitation, and ventricular scar burden to assist in risk stratification for ICD placement.

Diagnostic Techniques and Their Most Important Findings:

CMR was performed on a 1.5T scanner. Axial images were obtained as gradient echo (GRE) sequences and multiplane cine images were obtained with bSSFP. The axial GRE images demonstrated a round, well circumscribed MR dark lesion on the inferior left ventricular (LV) wall, mid-myocardium, measuring 11 x 12 mm. The mass was non-mobile and remained MR dark on T2 weighted bSSFP (Figure 1). First pass perfusion imaging did not demonstrate any contrast uptake. The mass remained dark on inversion recovery FLASH angiography as well as on prolonged inversion time phase sensitive inversion recovery (PSIR), where a second smaller mass located in the trabeculations of the anterior mitral valve papillary muscle was noted (Figure 2). The mass appeared less well organized on the PSIR, raising the possibility of calcium deposition in the ventricle given the patient’s age. Delineation was done using non-contrast computed tomography which was negative for calcium in the LV. Given the patient’s recent EPS with LV VT ablation and the negative calcium on the CT the findings were deemed thrombus and therapy was initiated.  

PSIR further demonstrated substantial late gadolinium enhancement (LGE) along the ventricular septum and throughout the right ventricular outflow tract and right ventricular anterior wall. Prior to discharge a subcutaneous defibrillator was placed.

Learning Points from this Case:

Post EPS thrombus is a rare, but documented, procedural complication, and cardiac MR imaging is well-suited to identify these lesions in most cases. However, in adult patients who are at risk for intracardiac calcium deposition delineating between the two can be difficult. Calcium is diamagnetic and demonstrates many of the same tissue characterization properties as a thrombus. CT without contrast can help delineate these findings as calcium demonstrates a high signal on CT imaging compared to thrombus.