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From the *Department of Pediatrics (Section of Pediatric Cardiology), Division of Congenital Heart Surgery, Department of Anesthesiology, Baylor College of Medicine, Texas Children’s Hospital, Houston, Texas.
Address correspondence to Wanda C. Miller-Hance, MD, TX Children’s Hospital, Division of Pediatric Cardiovascular Anesthesiology, 6621 Fannin St., WT 19345H, Houston, TX 77030. Address e-mail to: wmh{at}bcm.tmc.edu.
A 6-mo-old infant was referred for closure of a ventricular septal defect (VSD). Transthoracic echocardiography obtained for evaluation of a cardiac murmur at 2 mo of age demonstrated a large perimembranous VSD. Subsequent examination revealed partial occlusion of the defect by surrounding aneurysmal tissue, billowing of this tissue into the right atrium (RA), and the concern for a left ventricular (LV)-to-RA communication. Surgical intervention was undertaken in view of the clinical evidence of a moderate intracardiac shunt.
After induction of anesthesia, transesophageal echocardiography (TEE) was performed. Two-dimensional imaging demonstrated a large, septated, cystic mass in the posteroinferior aspect of the RA (Fig. 1; please see video clip available at www.anesthesia-analgesia.org). Color flow Doppler interrogation identified shunting from the LV into the saccular structure, and from this into the right ventricle (RV) (Please see video clip available at www.anesthesia-analgesia.org). No tricuspid inflow obstruction was detected. A second area of left-to-right shunting was noted in the adjacent membranous ventricular septum.
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Surgical inspection demonstrated aneurysmal fibrotic degeneration of the atrioventricular (AV) membranous septum protruding into the RA. Fenestrations in the aneurysmal sac, in immediate proximity to the tricuspid valve (TV), appeared to allow for the egress of blood directly into the RV. Two distinct anatomic communications were identified in the membranous septum: one between the LV and aneurysmal sac within the RA, and another between the ventricles. The intervention consisted of pericardial patch closure of the defects and repair of a TV leaflet incision required for anatomic exposure. Because of the concern for creating AV block, the aneurysmal tissue could not be resected in its entirety and a few fenestrations remained on the septal aspect of the tricuspid annulus. Postoperative TEE demonstrated a smaller aneurysmal sac, mild tricuspid regurgitation, and no evidence of residual septal defect shunting. Agitated saline injection into a central venous catheter showed a small systolic stream from the RV into the aneurysm, consistent with residual fenestrations along the septal TV leaflet (Please see video clip available at www.anesthesia-analgesia.org).
The membranous ventricular septum is divided by the attachment of the septal leaflet of the TV into two components: the AV portion, or region immediately superior to the TV separating the LV from the RA, and the interventricular portion, located inferiorly (Fig. 2A). The location of the aneurysm in this case was considered atypical as these are more likely to occur in the interventricular septum in association with perimembranous defects (Fig. 2B) (1,2). Aneurysms may limit intracardiac shunting and, in some cases, result in spontaneous defect closure. Associations include tricuspid regurgitation, obstruction to blood flow, systemic embolization, endocarditis, and conduction disturbances. The characteristic outpouching or windsock appearance on echocardiography results from aneurysmal distension during ventricular systole. The etiology of this anomaly is poorly understood; however, theories suggest either abnormal embryologic development or weakness of the affected tissues. Although unusual, we suggest that an aneurysm of the AV membranous septum may be considered in the differential diagnosis of a RA cystic mass.
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A LV-to-RA communication, also referred to as a "Gerbode defect," is a rare lesion. The malformation has been classified based on whether the defect that allows for shunting is located above (supravalvular) or below (infravalvular) the level of the TV (Fig. 2C) (3). In rare cases, both types may be present. In the more common defect, blood courses from the LV into the RV through an interventricular communication (infravalvular defect), being quickly diverted through an associated deficiency in the TV into the RA. The valve abnormality may result from a congenital malformation, cleft, perforation, or widened commissure. This produces the physiologic effect of a LV-to-RA shunt. In the least common form, a communication is present in the AV septum (supravalvular defect) (4). This may result from endocarditis, trauma, valve replacement, or ischemic heart disease. Echocardiography typically demonstrates systolic expansion of the RA and a high systolic pressure gradient across the defect as the high-pressure LV ejects into a low-pressure RA (5).
Although, in this case, a defect was present in the AV septum, the aneurysmal tissue contained the blood flow, functionally resulting in a ventricular shunt as LV blood coursed through the defect into the aneurysmal sac and from this into the RV. This was in addition to shunting through an adjacent defect in the interventricular membranous septum (perimembranous VSD). A ruptured sinus of Valsalva aneurysm into the RV or RA was considered an unlikely diagnosis based on the clinical course, in addition to findings such as a normal-appearing aortic valve and sinuses, the absence of continuous flow from the aorta into the cardiac chambers, and the multiple septations and areas of shunting identified.
Cross-sectional TEE views particularly useful in the assessment of defects in the membranous septum include the midesophageal four chamber, long axis, aortic valve short axis, and RV inflow–outflow views. A frame-by-frame analysis of the images is essential when multiple color Doppler jets are identified. Guided by the location of the communication, associated pathology, and the nature of the surgical intervention, the examination should consider the evaluation of valvar competency, assessment of patency of outflow tracts, and determination of ventricular systolic function. The immediate postbypass examination should consist of imaging of the ventricular septum in multiple planes, coupled with color flow Doppler interrogation to exclude residual shunts. Saline contrast echocardiography is of benefit in the assessment of complex defects or when equivocal color Doppler signals suggest residual shunting. Although the identification of contrast material within the LV should have raised concerns for a residual shunt (right-to-left direction), the more likely finding in this setting would be that of a negative contrast effect as noncontrast-containing blood from the higher pressure LV displaces contrast-containing blood in the RV (left-to-right shunt).
As demonstrated through extensive clinical experience and documented in the literature, this report illustrates the utility of TEE in the structural assessment of congenital heart disease and the intraoperative evaluation of intracardiac shunts.
Footnotes
Accepted for publication August 10, 2007.
Reprints will not be available from the author.
This article has supplementary material on the Web site: www.anesthesia-analgesia.org.
REFERENCES
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