Ventricular Septal Defect

Ventricular septal defects occur anywhere along the ventricular septum and their size and 
location determine the clinical manifestations. When viewed from right ventricular aspect, 
VSDs can be described as located at inlet, muscular, perimembranous, or outlet portions of 
the septum. The defects can be single, multiple or associated with other congenital heart 
disease. While exact prevalence is not precisely known, the defects comprise between 15 - 
30% of all congenital heart disease. Etiology is not known, but is likely multifactorial 
and different for the different types of VSDs. Rates for congenital heart disease among 
siblings of children with VSDs are between 0.5% and 2% . 
Embryologically, VSDs occur when there is a delay in closure of the ventricular septum 
beyond the first seven weeks of organogenesis. VSDs are more common in premature infants 
than full-term. Certain types of VSDs are found in persons of specific heritage, for 
example doubly committed subarterial VSD are more common in patients of Asian descent. 


NOTES:

Location
An inlet VSD lies in the posterior portion of the ventricular septum beneath the tricuspid 
valve. These defects may occur in isolation or may be associated with defects of the atrial 
primum and be a component of the atrioventricular septal defect (to be discussed below). 
Patients with inlet ventricular septal defects may demonstrate a superior axis on 
electrocardiogram. 
Defects may occur in the muscular portion of the trabecular ventricular septum, inferior to 
the septal band or superior to the septal band. These are referred to as muscular 
ventricular septal defects. They may be singular and small or alternatively can be multiple 
with significant hemodynamic effects. The former tend to have a high incidence of 
spontaneous closure, while the latter can be complicated, an in the most severe 
manifestation, give a "Swiss cheese" appearance to the ventricular septum. 
The most common type of ventricular septal defect is the perimembranous defect that is also 
referred to by some as conoventricular. These defects are of varying size, and occur 
beneath the aortic valve on the left side of the septum, entering into the right side under 
the septal leaflet of the tricuspid valve. This defect can be associated with congenital 
abnormalities of the aortic valve, or alternatively, the cause of structural abnormalities 
of the valve. These defects can be associated with the formation of aneurysm tissue along 
the right ventricular side of the septum. It is thought that this results from the 
apposition of the septal leaflet of the tricuspid valve against the ventricular septal 
defect. Over time, the progressive development of this aneurysm tissue may be responsible 
for the spontaneous closure of some perimembranous septal defects. At the same time, the 
close association of the septal leaflet of the tricuspid valve and the perimembranous 
septal defect may lead to structural and functional damage of the tricuspid valve. 
Defects of the perimembranous septum may be associated with malalignment of the great 
arteries and the ventricles. When the septum and great arteries are malaligned, two 
clinical ramifications may occur. First, there will be emptying of both ventricles into the 
overriding great artery, the degree of which depends on the size of the defect and the 
degree of malalignment and subsequent great artery override. Secondly, there is an 
increased likelihood of ventricular outflow obstruction. With anterior malalignment, the 
right ventricular outflow may become dynamically obstructed, and with posterior 
malalignment, the left ventricular outflow may become obstructive. 
Finally, defects may be found in the outflow portion of the right ventricle above the 
crista supraventricularis. These are known as doubly committed subarterial, conoseptal 
hypoplasia or supracristal ventricular septal defects. These defects are directly beneath 
the aortic valve on the left ventricular side of the septum and empty below the pulmonary 
valve in the infundibulum on the right ventricular side. These defects are associated with 
aortic valve prolapse, which may lead to aortic valve insufficiency. These defects are 
found more commonly in people of Asian descent. 

Hemodynamics:

During fetal development, ventricular septal defects, both large and small, do not 
generally cause hemodynamic difficulty. Because of the high pulmonary vascular resistance 
in the pulmonary circuit and the large ductus arteriosus allowing for equilibration of 
right and left ventricular pressures, there is typically minimal shunt across any 
ventricular septal defect in utero. In fact, small defects are notoriously difficult to 
visualize with fetal echocardiography, even with the use of color flow Doppler mapping, as 
there is very little shunt across the defect. 
With birth, the pulmonary circulation increases dramatically as the low resistance placenta 
is removed, the lungs inflate with air, the pulmonary vascular resistance begins to fall 
and the organ of oxygenation is transferred from the placenta to the lungs. As the ductus 
arteriosus closes in the first hours or days of life, there is separation of the pulmonary 
and systemic circulation allowing for discrepancy between the pulmonary and systemic 
resistances and the resulting changes and differences in right and left ventricular 
pressures. The pulmonary vascular resistance continues to fall in neonatal and early 
infancy as the pulmonary vasculature remodels, intra-acinar arterioles multiply and are 
arranged in parallel, and the infant develops a normal physiologic anemia. All of these 
changes lead to a systemic resistance that exceeds the pulmonary resistance, a 
corresponding decrease in the right ventricular pressure, and a pressure gradient between 
the left and right ventricle. Progressive shunting across a given ventricular septal defect 
will ensue as the pressure difference between the ventricles increases with the passage of 
time. The size of the defects and to some degree its location will determine the clinical 
manifestations. 
With small ventricular septal defects, the pressure gradient is well maintained between the 
left and right ventricle and with each systole, there shunt of blood from the high pressure 
ventricle to the lower pressure chamber. While the shunt may be small in the small defect, 
the high pressure gradient will produce significant turbulence of blood as it moves from 
left to right. This turbulence will produce the murmur on auscultation, and as a result, a 
small ventricular septal defect often has a loud, easily audible systolic murmur. This 
murmur is frequently holosystolic as there is flow throughout systole Ð from the onset of 
AV valve closure through the closure of the semilunar valves. 
With larger ventricular septal defects, the volume of the left to right shunt will increase 
as the pulmonary vascular resistance falls during infancy. Because the larger size of the 
defect does not restrict flow, the pulmonary arterial bed is exposed to this high volume of 
flow and to a higher pressure than would be present in the absence of a ventricular septal 
defect. In fact, in truly large ventricular septal defects, the pulmonary artery pressure 
will equal the aortic pressure (if there is no obstruction to either systemic or pulmonary 
blood flow), as the defect allows for equalization of pressures between the two ventricles. 
While the flow across the defect may be high in large ventricular septal defects, the 
turbulence is minimized, as there is no significant pressure gradient between the two 
ventricles. As a result, the large ventricular septal defect may not produce a significant 
murmur from its flow. However, one may appreciate turbulence across the pulmonary outlet 
from the increased volume of blood being ejected into the pulmonary artery. In addition, 
there may turbulence across the mitral valve during diastole as the volume of blood 
returning from the lungs is significantly increased. 
Ventricular septal defects produce almost all of their shunting during systole when the 
ventricles are exposed to increasing pressure as the ventricles are depolarized and then 
exposed their downstream resistances as the semilunar valves open. While the defect 
obviously exists during diastole, the ventricular pressures are often nearly if not equal 
so that there is essentially no shunting during this phase of the cardiac cycle. The 
isovolumic phase of ventricular systole does not truly exist as there is communication 
between the ventricles and their volumes will change. Shunting continues from this early 
phase of systole through its completion when the semilunar valves close. While ventricular 
septal defects do in fact shunt blood from the high pressure left ventricle to the lower 
pressure right ventricle, it is the pulmonary circuit that experiences the true volume 
load. Again, during systole, the right ventricle is contracting, ejecting its contents into 
the pulmonary artery so that it essentially serves as a conduit for the left ventricular 
blood to enter the pulmonary artery. As a result, the pulmonary artery, the pulmonary 
capillaries, the pulmonary veins, the left atrium and left ventricle all become volume 
loaded and dilate in response to a significantly large ventricular septal defect. 


Natural History:

Spontaneous Closure
Many ventricular septal defects become smaller and even close spontaneously with time. 
Defects in the muscular septum often close by what is thought to be a process on ingrowth 
of muscle at the margins. Some defects in the conoventriclular septum diminish in size by 
the development of fibrous tissue at the margins of the defect coupled with adhesion by 
some components of the septal leaflet of the tricuspid valve. This process has been 
referred to as aneurysm formation, and this is generally a favorable sign that the 
ventricular septal defect is becoming progressively more restrictive to flow and may even 
close spontaneously. 
The exact frequency with which ventricular septal defect closes is not clearly known, 
though it has been shown that as many as 70% of all ventricular septal defects diagnosed at 
birth will undergo resolution. This most typically occurs within the first year or two of 
life, but may continue to occur through childhood. Though most small defects undergo 
spontaneous closure during childhood, not all do. Therefore, a significant number of adults 
have small, asymptomatic ventricular septal defects. Some may continue to undergo closure, 
even well in to adulthood. 
Other ventricular septal defects are unlikely to close spontaneously. These would include 
the malalignment ventricular septal defects and the AV canal type or inlet ventricular 
septal defect among others. When these defects are not surgically addressed, morbidity and 
mortality are extremely likely to ensue. 
Pulmonary Hypertension 
In those patients that survive into adult life with an unrepaired large ventricular septal 
defect, pulmonary hypertension is almost always present and leads to significant morbidity 
and mortality in these patients. The clinical features of EisenmengerÕs syndrome with 
reversal of ventricular flow from right to left typically occur in late childhood or early 
adolescence. While these individuals may survive into their third and fourth decade, they 
will suffer from complications resulting from pulmonary vascular disease in the face of 
intracardiac shunting including cyanosis, resultant polycythemia, clubbing, risk of 
paradoxical emboli and other debilitating symptoms. 
Infective Endocarditis 
The risk of infective endocarditis in patients with ventricular septal defects, even those 
that are small is relatively high. In fact, small defects may be at higher risk than larger 
ones because of the increased turbulence at the margins of the small defect. The risk of 
endocarditis with a ventricular septal defect is in general on the order of 2.5 per 1000 
patient-years. Those patients with ventricular septal defect who have had a proven episode 
of infective endocarditis are most probably at higher risk for a recurrent infection. 
Aortic Valve Disease 
Ventricular septal defects of the conoseptal hypoplasia type, with little or no supporting 
tissue under the semilunar valves (so called doubly committed subarterial defects) may be 
associated with progressive aortic valve disease. As the high velocity stream of blood 
moves from the left ventricle to the right ventricle, there is a force applied to the 
aortic valve which forms a boarder of the defect. Over time, this force, known as the 
Venturi effect, distorts and pulls the aortic sinus and valve leaflet into the defect. 
While this process may serve to partially occlude the defect and minimize the shunt, it 
frequently leads to progressive damage to the aortic valve structure and valvular 
dysfunction. This is marked by aortic valve insufficiency, which steals blood from the 
aorta during diastole and by a progressive volume load on the left ventricle. This process 
usually begins in the first decade of life but may be seen later in life as well. While 
this is most commonly seen in defects of the doubly committed subarterial type, it can also 
be seen in defects of the conoventricular type if the defect lies immediately adjacent to 
the aortic valve. 

Clinical Notes:PRESENTATION

Patients with ventricular septal defect have a history, presentation and physical 
examination that typically reflects the size of the ventricular septal defect. Most infants 
with a ventricular septal defect are symptomatic in the neonatal period regardless of the 
size of the defect as their pulmonary vascular resistance is still relatively high, and the 
volume of shunting is relatively low. Most will feed and thrive in the first weeks of life. 
However, as the pulmonary vascular resistance continues to fall through the first month of 
life, the volume of left to right shunting progressively increases and signs and symptoms 
will become apparent. 
It is important to note that while ventricular septal defects typically occur in otherwise 
normal children, they can be seen in a wide variety of chromosomal defects and non-cardiac 
pathologies. Therefore, a complete and thorough history and physical examination is 
essential when evaluating a child suspected on having a ventricular septal defect. 
Small ventricular septal defects 
The most common finding in a patient with a small ventricular septal defect is a systolic 
murmur noted by the primary care provider, often at the two week or week visit, when the 
pulmonary vascular resistance has fallen more significantly. The history is most often 
remarkable only for the completely normal growth, development, and behavior and feeding 
pattern of the infant. The family history may reveal others with a history of ventricular 
septal defect. 
On physical examination of the patient with a small ventricular septal defect, the 
precordium is quiet on palpation. With auscultation, the first and second heart sounds are 
normal. A harsh, high-pitched systolic murmur, which may be short or pansystolic is usually 
heard over the area of the defect. There may be a thrill noted as well, particularly as the 
pulmonary vascular resistance continues to fall. The pulses and perfusion should be normal. 
There should not be findings in pulmonary system and the liver is not enlarged. 
Large ventricular septal defects 
In patients with a larger ventricular septal defect, symptoms may develop toward the end of 
the first month of life. As the pulmonary vascular resistance continues to fall, there is 
increasing pulmonary blood flow. This increasing flow leads to increased pulmonary venous 
return to the left atrium, which begins to dilate, and as it does, its pressure rises. This 
leads to increasing congestion of the pulmonary veins and pulmonary capillaries which may 
become engorged. Tachypnea will be common in these infants, as will dyspnea and feeding 
difficulties. In fact, the tachypnea leads to increased calorie consumption and also makes 
sucking and obligate nose breathing much more difficult Ð leading to decreased caloric 
intake. This produces a marked discrepancy between caloric supply and demand, and it is 
typical for such infants to present with failure to feed well, gain weight and thrive. The 
combination of the increasing pulmonary symptoms and the feeding and growth disturbance is 
characteristic of congestive cardiac failure in the infant and these symptoms typically 
occur between 2 and 6 weeks of age. 
On physical examination, the infant with a large ventricular septal defect is usually found 
to have a hyperdynamic precordium. This may be associated with a palpable systolic impulse 
as the left sternal edge. This is the result of the high pressure right ventricle. As the 
volume of the shunt increases, there may be a mid-diastolic murmur at the apex resulting 
from increased flow across the mitral valve. The second heart sound may become accentuated 
and P2 may become loud as pulmonary hypertension progresses. As congestive failure 
progresses, a gallop rhythm may become evident. 
Non-cardiac findings on examination include the findings of tachypnea, subcostal and 
intercostals retractions. With marked cardiac congestion and high pulmonary pressures, the 
liver may become congested and palpable below the costal margin. In addition, subcutaneous 
fat stores are minimal and the patients weight will likely be abnormally low. 

Diagnostic Tests:

Echo:
Virtually all VSDs should be well visualized by echocardiography. 2-D real-time 
echocardiography and color Doppler flow mapping allow for accurate assessment of the 
precise location of the defect as well as an estimation of the volume of shunting which it 
allows. Pulsed and continuous wave Doppler measurements of the shunt flow, in combination 
with measurement of regurgitation of the tricuspid and pulmonary valves should allow for an 
estimate of the pulmonary artery pressure. While some of the larger defects may be seen 
from all standard echocardiographic windows, some defects may be seen best in certain 
imaging planes. 
The conoventricular defects are best visualized from the parasternal long axis, apical four 
chamber and subcostal view as these windows profile the membranous septum which lies just 
beneath the aortic valve. Doppler estimation of the pressure gradient between the two 
ventricles is best achieved with the Doppler interrogation beam parallel to the flow from 
left to right ventricle. This is often easiest to obtain in the parasternal short axis 
view. 
The defects of the muscular ventricular septum can be seen from the parasternal long axis, 
short axis, apical four-chamber and subcostal view. Sometimes the only way to identify a 
muscular defect that is small is with the use of color flow mapping techniques. To some 
degree, the location of the defect within the muscular septum will determine which of these 
windows is most advantageous for analysis of the defect. Like the conoventricular defect, 
estimation of the pressure gradient between the right and left ventricle in the muscular 
septal defects is usually best obtained from the parasternal short axis. 
VSDs which are doubly committed subarterial and represent conoseptal hypoplasia, are 
usually well profiled from a parasternal long axis, short axis and subcostal view. In the 
subcostal and short axis view, the defect will be seen in the right ventricular outflow 
tract. It is important to thoroughly evaluate these patients for any evidence of aortic 
valve prolapse, specifically of the right coronary cusp, and for aortic regurgitation. 
Defects of the posterior inlet septum are usually best seen from the apical four-chamber 
and the subcostal view, both of which image the posterior cardiac structures. The septal 
leaflet of the tricuspid valve may partially obscure these defects, making them appear 
smaller than they actually are. However, the application of color flow Doppler mapping will 
demonstrate the shunting adequately even if there is tricuspid valve involvement in the 
defect. 
Transesophageal echo (TEE) provides outstanding imaging of the cardiac structures including 
the ventricular septum, defects therein, their size and their relationship to the 
atrioventricular and semilunar valves. However, because of its relative invasive nature, it 
is utility in the young patient with a ventricular septal defect is perhaps greatest in the 
operating room. 
Fetal Echo can accurately diagnose the presence of a large ventricular septal defect, 
especially those of the conoventricular type with and without malalignment, and those of 
the inlet septum. However, small defects, especially those in the trabeculated muscular 
septum may be virtually impossible to visualize with current fetal echo techniques. 
ECG:
The ECG is reflective of the size and hemodynamic effect of the VSD. In children with small 
ventricular communications, the ECG will be normal for age. With increasing defect size and 
the resulting shunting, there will be left ventricular hypertrophy noted. With 
unrestrictive large ventricular septal defects which allow the right ventricular pressure 
to reflect that of the left ventricle, there may also be right ventricular or combined 
ventricular hypertrophy on the electrocardiogram. P wave changes consistent with left 
atrial enlargement may also become evident. Ventricular septal defects of the posterior 
inlet septum often demonstrate a superior frontal QRS axis on the limb leads of the 
electrocardiogram. 
Chest x-ray (CXR) 
CXR reflects the size of the ventricular septal defect and the resistance of the pulmonary 
vasculature. The CXR in the patient with a small muscular ventricular septal defect would 
be expected to be normal, with no significant changes in chamber size or pulmonary 
vascularity noted. With the progressive increase in left to right flow across a ventricular 
septal defect, the chest radiograph will demonstrate left heart chamber enlargement. The 
left ventricular apex may be displaced laterally and inferiorly, a result of left 
ventricular dilatation. If the left atrium is enlarged, it may produce flattening of the 
left main bronchus and a double shadow over the right atrium. In addition, there will be 
progressive hyperinflation of the lungs, which represents early pulmonary edema as well as 
a progressive prominence of the pulmonary vasculature. This is often best appreciated in 
the apices of the lungs, and is sometimes referred to as shunt vascularity. 

Treatment:

Management of VSD patients depends entirely on the clinical manifestations of the 
hemodynamic effects of the shunt. Small defects will require no therapy and will often 
undergo spontaneous closure by age 10. Moderate and large defects may initially be managed 
medically with anticongestive pharmacological therapy such as Digoxin, diuretics and 
afterload reduction. 
As the pulmonary vascular resistance continues to fall, and the volume of left to right 
shunting progresses, some patients will have congestive heart failure, which cannot be 
managed with medical therapy alone. These patients are then referred for surgical repair of 
their ventricular septal defects. Whenever possible, a trans-atrial approach from the right 
atrium is preferable to a ventricular incision. 
Patients with posterior inlet ventricular septal defects are at an increased risk for the 
development of heart block following surgical intervention.