Left Ventricular Outflow Tract to Right Atrial Fistula Diagnosed by Intraoperative Transesophageal Echocardiography
2007-01-19

A 68-yr-old male with increasing shortness of breath and a history of aortic stenosis was admitted. A transthoracic echocardiographic examination (TTE) revealed an aortic valve (AV) area of 0.62 cm2. The patient was subsequently scheduled for an AV replacement (AVR). Cardiac catheterization performed on the morning of surgery demonstrated single vessel coronary artery disease involving the right coronary artery. The patient underwent an uncomplicated AVR (#23 Carpentier-Edwards Magna) with a single vessel coronary artery bypass graft. His initial postoperative course was uncomplicated, but on postoperative day 3 he became febrile to 38.7°C. Blood cultures were positive for Staphylococcus aureus and antibiotic therapy was initiated. TTE at that time was inconclusive, however transesophageal echocardiography (TEE) performed in the intensive care unit on postoperative day 7 was interpreted as a fistulous communication between the aorta and right atrium (RA) associated with a periannular abscess in the vicinity of the AVR. The patient returned to the operating room where intraoperative multiplane TEE demonstrated that the fistula actually communicated between the left ventricular outflow tract (LVOT) and the RA. In the midesophageal four-chamber view at 0° rotation, the diameter of this tract was approximately 0.5–0.8 cm. (Fig. 1 Top). Color flow Doppler in the midesophageal (Fig. 1 Bottom) and deep transgastric long-axis (Fig. 2) views confirmed the presence of turbulent flow from the LVOT to the RA just above the tricuspid valve (see video loop for midesophageal TEE views available at www.anesthesia-analgesia.org). Therefore, the surgical approach was changed to a replacement of the original AV prosthesis and aortic root with a #22 homograft (LifeNet), and the fistula closed by sewing bovine pericardial patches to both sides of the tract. The patient was discharged from the hospital in good condition after a subsequent uneventful postoperative course.Figure 1.: Top: Midesophageal four-chamber transesophageal echocardiographic (TEE) view at 0° rotation demonstrating a fistula (→) from the left ventricular outflow tract (LVOT) to the right atrium (RA). Bottom: Midesophageal four-chamber TEE view at 0° rotation with color flow Doppler showing turbulent flow from the LVOT into the RA.Figure 2.: Deep transgastric transesophageal echocardiographic (TEE) view at 0° rotation showing a communication between the left ventricular outflow tract (LVOT) and right atrium (RA). Turbulent flow from the LVOT into the RA at the level of the tricuspid valve is demonstrated (→).Communications between the LVOT and RA are mostly congenital and are known as "Gerbode's defect" (1). This anomaly accounts for <1% of all congenital heart lesions. Similar acquired shunts may develop after chest trauma, mitral and AV replacement, or infective endocarditis (2). The communication results from a defect in the interventricular septum, inferior to the crista supraventricularis. Patients with this lesion can present with hemodynamic deterioration, myocardial injury, prosthetic valve dysfunction, or perivalvular leaks. Symptoms of right-sided heart failure dominate the clinical picture and depend on the magnitude of the shunt as a reflection of the size of the defect. Physical findings include a harsh holosystolic murmur and right ventricular heave. Only patients with small shunts remain asymptomatic. Collateral injury associated with a perivalvular infection can involve the subannular region and membranous interventricular septum (3). TTE often fails to identify the involvement of these subaortic structures (4). The creation of a TTE window to visualize the membranous septum can be technically challenging because of patient anatomy and beam orientation. An overlying aortic prosthesis that overshadows the lesion can also complicate transthoracic imaging. Therefore, a comprehensive TEE examination using two-dimensional and color flow Doppler imaging can be useful for delineating the location of the pathology and for guiding the surgical procedure.