Aneurysm of the atrioventricular septum mimicking a right atrial mass with thrombus is uncommon and a handful of reports have been described [1, 2]. We present a rare case of an incidental finding in transthoracic echocardiography (TTE) of a right atrial tumor mimicking myxoma above the septal leaflet of the tricuspid valve in the membranous septum, in a 65-year-old male asymptomatic patient. No left-to-right shunt was observed (Figures 1 A, B). The TTE was performed as part of preventive examinations. Intraoperatively, a left ventricular-right atrial communication (Gerbode-type defect), accompanied by an aneurysm of the atrioventricular septum filled with thrombus, was found in the right atrium (Figure 1 C). Histology confirmed the finding (Figure 1 D). He underwent successful extirpation of the tumor and closure of the communication between the right atrium and the left ventricle. Moreover, other right atrial masses that can present as myxoma on imaging include benign and malignant primary cardiac tumors, metastatic cardiac tumors, a prominent eustachian valve, sessile or mobile thrombi, vegetations of the tricuspid valve, and different intracardiac objects (pacemaker leads, central venous catheters, needles, and even bullets) [3].
Figure 1
A, B – Echocardiographic images showing the right atrial atrioventricular septal aneurysm; C – intraoperative image; D – histological image showing the thrombus and the interventricular septum
RV – right ventricle, RA – right atrium, LVOT – left ventricular outflow tract, LA – left atrium, SVC – vena cava superior, TV – tricuspid valve, IVS – interventricular septum.
In conclusion, we have presented a rare form of a Gerbode-type defect, accompanied by an aneurysm of the membranous septum. This case is of importance because the Gerbode-type defect was atypical, asymptomatic, with no left-to-right-shunt, accompanied by an aneurysm of the membranous septum filled with thrombus. The mechanism of the septal perforation is contradictory. The supravalvular form of the Gerbode-type defect, as in our case, is more likely to be acquired, whereas membranous septal aneurysm usually appears with congenital-type ventricular septal defects [4].
