Gradual Enhancement of a Large Left Atrial Papillary Fibroelastoma on Cardiac Magnetic Resonance

A 70-year-old man underwent cardiac magnetic resonance (CMR) after a left atrial mass was discovered on echocardiography. A mobile, 3 × 2.6 × 2.9-cm, T₂-bright mass was present at the base of the left atrial appendage, abutting the opening of the left superior pulmonary vein. The mass was not visible either on pre-contrast T₁-weighted dark-blood images or on pre-contrast steady-state free precession bright-blood images (Fig. 1). Serial post-contrast imaging revealed very gradual centripetal enhancement (Fig. 2). Because the imaging features were not typical for thrombus, the mass was believed to be a benign tumor, such as a myxoma.

Fig. 1 Transaxial cardiac magnetic resonance images through the left atrium (LA), using A) T₁-weighted, B) steady-state free precession, and C) T₂-weighted imaging. The LA mass is not seen in A or B but is clearly identified in C (arrow).

Ao = ascending aorta

Fig. 2 Transaxial, T₁-weighted, inversion-recovery, gradient echo images of the left atrial mass at A) ∼30 sec, B) 3 min, C) 7 min, and D) 20 min after gadolinium-based contrast injection. Although A shows no enhancement of the mass, the subsequent images show progressive centripetal enhancement (arrows), confirming that the mass is not a thrombus.

The mass was excised. Intraoperative transesophageal echocardiography showed many important features of the mass (Fig. 3). On gross pathology, the mass was gelatinous and friable. Immunohistochemical staining led to the diagnosis of a very large papillary fibroelastoma, the 2nd most common benign primary tumor of the heart (after myxoma).^1–4

Fig. 3 Static transesophageal echocardiographic diastolic-phase image shows the relationship of the mass (arrow) to the left superior pulmonary vein (PV) and the left atrial appendage (LAA).

MV = mitral valve

Real-time motion image is available at www.texasheart.org/journal.

Comment

Papillary fibroelastomas are usually small (<1 cm) and mobile and are frequently attached to valve leaflets, although they can be found on any endocardial surface. Their enhancement is typically most distinct on CMR, and they usually have a low T₂ signal. The risk of embolization necessitates their prompt surgical removal after detection.^4,5

Cardiac magnetic resonance is useful for delineating most of the important aspects of masses in or around the heart, including their size, site, and breadth of attachment. It can also delineate their mobility, functional significance, tissue characterization, and enhancement pattern (which usually distinguishes a tumor from thrombus). However, this case reveals 2 important pitfalls of CMR: even large lesions might be stealthy on some pulse sequences, and serial post-contrast imaging might be necessary to determine the presence or absence of enhancement. As a consequence, typical papillary fibroelastomas—as well as other small, mobile masses—might be missed on routine CMR.