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.