DISCUSSION
The Gerbode defect is a rare communication between the heart chambers,which connects the left ventrical to the right atrium.It was named after Gerbode1successfully performed the operation in five patients in 1958.Initially,the author illustrated that the lesion consisted of a high ventricular septal defect associated with a defect of the septal leaflet of the tricuspid valve which allowed left ventricular blood to enter the right atrium. But gradually this special type of VSD causing a LV-to-RA shunt is all called Gerbode defect whether it accompany with the defect of the septal leaflet of the tricuspid valve or not2.The cause of the defect can be congenital or aquired.Aquired defect is often a complication of endocarditis3, myocardial infarction4, blunt chest trauma5 or cardiac surgery6. Acquired LV-RA communication is increasingly being reported. The LV-to RA shunt accounts for only 0.08% of intracardiac shunts7 and <1% of all congenital cardiac defects8. Congenital Gerbode defect is so rare that researchers observed only six cases at the Children’s Memorial Hospital in Chicago between 1990 and 20082. Riemenschneider and Moss9 have described two types of LV-RA communication based on whether the communication is direct or indirect(though the tricuspic valve). According to the location of the defect, Sakakibara and Konno10 classified it into 3 types.Type 1,also called the direct type without tricuspic regurgitation, is a supravavular defect occuring in the atrialventricular septum above TV.Type 2 is a infravavular defect occuring in the memberous, muscular intraventricular septum or endocardial cushion below the TV.The shunt of this type defect was often confused with the tricuspic regurgitation,so it was called the indirect type.Type 3 is an intermediate defect with both supravalvular and infravalvular components.The type 2 and 3 may have many variants to septal leaflet anomalies of the TV, including a cleft, widened commissural space, perforation,abnormal chordae and other deformities. Type 1 is common in acquired cases but congenital type is very rare. This case was a congenital type 1 defect2,11.
Echocardiography is the most useful diagnosis method and is noninvasive and radiation-free. In ordinary VSD, we could usually find the blood flow goes directly into the right ventricle during the systole but doesn’t last until diastole and the pulmonary artery congestion and right ventricle enlargement is usually happen before the right atrium enlargement. Silbiger12et al discribed clues suggesting the presence of a Gerbode shunt include (1) atypical jet direction, (2) persistent shunt flow into diastole, (3) the absence of ventricular septal flattening, (4) the absence of right ventricular hypertrophy, and (5) the presence of a normal diastolic pulmonary artery pressure estimated from the pulmonic regurgitant velocity. Cardiac magnetic resonance (CMR) is one of the adjuvant techniques to reveal further detailed anatomical and physiological information, but it is expensive and uneasy to obtain for children . Cardiac catheterization is invasive, so it is not necessary for diagnosis unless to evaluate the hemodynamics and pressure.
Some researchers recommend that the treatment of this defect is according to the severity of symptoms which is associated with the size ,location, magnitude of shunt, flow volume, development time magnitude of shunt. Asymptomatic, without circulatory overload or small defects with insignificant intracardiac shunt could be managed conservatively by following up rather than surgery2. But in our opinion, continuous shunt not only increase the load of the heart, but also increase the risk of infective endocarditis and the surgery is safe, so we advocate to treat it no matter whether the symptom is significant or not.The treatment includes the transcatheter closure and the patch closure surgery. The percutaneous transcatheter closure techniques has been used mostly in acquired cases11,13or high-risk surgical candidates due to previous valve replacement, advanced age, anticoagulation, and multiple comorbidities14. The LV-to-RA communication was corrected by surgery traditionally and surgical closure has been demonstrated to be with excellent outcome and recommended for closure of all direct defects2. In this case,the little girl had some symptoms of right ventricle overload including sweating and poor appetite.The size of the lesion(11.3mm) and the magnitude of shunt was large for 2-year-old girl.Thus,we chose the patch to close the lesion.