A Gerbode defect is a very rare congenital anomaly. It is a ventricular septal defect communicating directly between the left ventricle and right atrium. This is anatomically possible because the normal tricuspid valve is more apically displaced than the mitral valve.
The definition of a Gerbode defect, according to the STS Congenital Heart Nomenclature and Database Project, is a true left ventricular-to-right atrial communication. The blood in the left ventricle goes through the small area of the membranous septum where there is the potential for a left ventricular-to-right atrial shunt. This communication is above the tricuspid valve.
The indirect type of communication is where the flow of blood is from the left ventricle through a ventricular septal defect into the right ventricle and then through a defect in the tricuspid valve into the right atrium. The source of this communication occurs below the tricuspid valve.
The first description of a direct communication between the left ventricle and the right atrium was reported by Buhl in 1857. The first successful closure of such a defect was first reported by Kirby (using hypothermia and inflow occlusion) at the Hospital of the University of Pennsylvania in 1956. The first successful series of patients operated on with a left ventricular-to-right atrial shunt was reported by Frank Gerbode, a noted surgeon at Stanford University.
The large systolic pressure gradient between the left ventricle and the right atrium would expectedly result in an unmistakeable high velocity systolic Doppler flow signal. Yet, the diagnosis is rarely reported in the literature.
One diagnostic echocardiographic pitfall is the mistaken diagnosis of Gerbode defect in a patient with a membranous ventricular septal defect. The flow from left ventricle to right ventricle can continue into the right atrium as a regurgitant jet.
A Gerbode defect should be suspected on echocardiogram when there is an unusually dilated right atrium. The other sine qua non of the Gerbode defect is the high Doppler gradient between the left ventricle and the right atrium. The mean gradient in our series was 95 mm Hg.
We recommend closure of essentially all Gerbode defects. In our experience, and surveying other pediatric cardiologists and cardiac surgeons, the spontaneous closure of these defects is very rare. The left ventricular-to-right atrial shunts cause these patients to have significant symptoms, and all of our patients had either congestive heart failure, failure to thrive, or exercise intolerance. The operation to close these defects is quite safe. The defect is away from the conduction system and in our series all patients were in normal sinus rhythm. There were no residual defects, no reoperations, and no significant tricuspid valve insufficiency. The Gerbode ventriculo-atrial defect is a rare defect with excellent surgical results.
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