“Ventricular Septal Defects” by Dr. David Bailly for OPENPediatrics

“Ventricular Septal Defects” by Dr. David Bailly for OPENPediatrics

August 17, 2019 23 By Bertrand Dibbert


Ventricular Septal Defects, by Doctor David
Bailey. Hello, my name is David Bailey. I’m a pediatric
cardiologist and pediatric cardiac intensivist. And today, we’re going to be talking about
ventricular septal defects. We’re going to start by outlining the anatomy and physiology
of this cardiac lesion, followed by typical and atypical presentations. And then we’ll
talk about the imaging and diagnostic workup. Finally, we’ll talk about the initial management
and pre-operative considerations for patients with ventricular septal defects. Anatomy and Physiology. So to begin with, a ventricular septal defect
is a defect that can occur anywhere along the ventricular septum. There can be one or
many, and it can occur in one location or even multiple locations. The nomenclature of ventricular septal defects
is known to be quite convoluted. Here we use five typical subcategories, the first being
muscular ventricular septal defects. This is the most common, it presents about 60%
of the time. And it’s important to know these different nomenclatures in as much as that
we now understand a little bit more about the natural history of each of these different
types of lesions. Muscular defects, again, as I said, is the
most common. They’re also the most likely type to close spontaneously. 30% of them,
in fact, close spontaneously. They also often present with multiple defects, which are sometimes
hard to see by echocardiography. The next most common type is membranous, also
known as peri- or peramembranous defects. And these account for about 30% percent of
the total of ventrical septal defects that we see. These lesions are less likely to close
on their own. However, sometimes tissue from the tricuspid valve will occlude the defect.
And so they will close in that circumstance. The last three types rarely, if ever, close
on their own. There’s the malalignment defect, as is usually seen with Tetralogy of Fallot.
And again, that really closes on its own. And it’s often seen in addition to other cardiac
lesions. There’s the subpulmonary or conal type of
ventricular septal defects. These ones will rarely close on their own, if ever at all.
Some people would say the diagnosis is an indication for surgical repair because they
close so rarely. And they’re more common in the Asian population. This is important because they’re also more
commonly associated with aortic regurgitation, which is more commonly associated with bacterial
endocarditis, before and even after repair. So for those of you practicing in those countries,
this is a lesion you may see more frequently. So keep in mind the increased instance of
endocarditis in that subcategory. And then finally, there’s the endocardial
cushion defects. This is classically seen in patients with atrioventricular canals and
obviously, the incidence of Trisomy 21 that is correlated with that specific lesion. We often talk about the size of ventricular
septal defects. We call them large, medium, and small. Large defects are simply those
which are greater than 50% the size of the diameter of the aorta. Small defects are typically
restrictive. And medium sized defect lie somewhere in between. Now the physiology ventricular septal defects
is very interesting. It’s a defect that shunts predominantly during systole, and then imparts
both a volume and a pressure load to the pulmonary circulation, and then to the left side of
the heart. So during systole, the heart squeezes, the
LV contracts and ejects blood if there’s an unrestricted defect into the right ventricle
at systemic pressures. The bulk of the blood is actually injected into the pulmonary artery
because the right ventricle is also undergoing systole at that same time. That pressure and that volume is imparted
to the pulmonary circulation, which returns to the left side of the heart. The increased
volume burden to the left side of the heart is evidenced by a left atrial and left ventricular
enlargement if the volume burden is significant. It is this volume burden and pressure burden
that causes the usual presentation that we see. Presentation. So how do these patients present? As you would
imagine, they present in congestive heart failure and pulmonary artery hypertension
if it’s longstanding and unchecked. The congestive heart failure is due to a few
things. The main determinants of the degree of congestive heart failure and failure to
thrive is the degree of shunt and the degree of work of breathing that’s imparted by that
shunt. So the cardiac output needed to maintain a
normal systemic circulation in the setting of increased pulmonary blood flow must be
increased. Therefore, the total cardiac output in the setting of a VSD is a significant contribution
to the metabolic demands needed by these patients. In addition to the increased pulmonary blood
flow, there’s an increased pulmonary metabolic demand from that work of breathing. Those
two things are the main determinants of congestive heart failure and failure to thrive in these
patients. Again, if the pulmonary circulation is left
unchecked, if the defect is not closed, or the P.A. Is not banded as it was in the past,
the contribution of a combined volume and pressure load to the pulmonary circulation
can lead to the development of early onset pulmonary hypertension. Sometimes even in
the neonatal period if there’s concomitant lesions. So what will these patients look like and
sound like when they walk into your office or when you see them in your hospital? They’ll
be maybe cachectic, have some increased work of breathing, easy tachypnea, they’ll be very
prone to respiratory infections due to the increased pulmonary blood flow. They’ll be
particularly vulnerable when they’re anemic. So, right around two months when they reach
their physiologic nadir, the anemia combined with the increased cardiac demands can cause
them to have more profound failure to thrive then you might expect. On physical exam, you’ll hear a pansystolic
murmur as blood is shunted across the ventricular septum [SOUND OF HEART BEATING] The murmur will begin right after the S1.
It may be slightly delayed if it’s a muscular defect with some constriction. The S2 is very
important to listen to and to characterize. If the S2 is accentuated, if it is palpable,
if it is singular, all those things denote an increase in degree of pulmonary hypertension.
And it’s important to understand the progression of pulmonary hypertension, especially in patients
with VSDs. If the pulmonary hypertension progresses to
a point that the pulmonary vascular resistance is higher than the systemic vascular resistance,
the shunt murmur will no longer be appreciated, and those patients are then categorized as
having Eisenmenger Complex. Other lesions that also present with VSDs
determine how they present. We talked a little about aortic regurgitation and the increased
incidence of bacterial endocarditis. The murmur from aortic regurgitation is rarely heard
before the age of five, even though the incidence of aortic regurgitation– we’re finding out
it’s more common now that we have better imaging modalities. Aortic Stenosis, some arch hypoplasia and
coarcation is also commonly seen with ventricular septal defects. And these patients may have
a click. They also may develop more pulmonary vascular congestion, due to L.A. Hypertension,
than some of your other patients. If you find an ASD with the patient, look
for extra cardiac defects, as they’re more common in patients who have both an ASD and
a VSD. And then there’s the double chamber right
ventricle that can often occur, most commonly in those with membranous ventricular septal
defects, due to hypertrophy of the muscle or the muscles around the moderator band itself.
The EKG and the chest x-ray, in combination with your physical exam finding, often are
not conclusive enough to diagnose a VSD with double chamber right ventricle, and it is
in this setting especially that echocardiogram is important. Imaging and diagnostic work-up. As far as imaging and diagnostic modalities
go, the work-up is pretty intuitive. The echo should donate the size of the lesion, the
location of the lesion, and the physiologic burden, the shunt, and the pressure of the
lesion. The EKG– you would look for signs of right ventricular elevated pressure or
left ventricular enlargements. And it’s the classic EKG findings of RVH and LVH that you
would see. If you see either one of those things, consider PS or a significant shunt
burden. The chest x-ray usually will show increased
pulmonary blood flow and congestion. However, you may see some hyperexpansion on the chest
x-ray, particularly, in those infants with left atrial enlargement from a large shunt
burden and often those who have a VSD and a ductus. The atrial enlargement can cause
bronchial compression and hyperexpansion by chest x-ray. The echo is a definitive tool
to make the diagnosis. And if there’s any question about the pulmonary artery pressures
or the characterization of the defect, then cath would be indicated. If pulmonary vascular resistance is markedly
elevated above normal limits of three woods units, closure may not be possible. If pulmonary
vascular resistance is within normal limits closure or continued medical management is
appropriate. Initial Management Strategies. The management
of these patients centers around treating the congestive heart failure, the failure
to thrive, and in close follow up again to understand the pulmonary vascular changes
that will be ongoing in these patients. In neonates and infants it is recommended
that if the defect is large or unrestrictive and there is any evidence of heart failure,
failure to thrive, or ongoing pulmonary hypertension to close the lesion at that time. If the infant
is able to get out to the six month period, and there’s no overt signs of heart failure
or pulmonary hypertension, medical management is very reasonable in this patient population.
Continued use of lasix and increasing caloric density of their formula are two of the mainstays
that we use here to allow them to grow. Particularly, if it is a muscular septal defect, which was
known to often close spontaneously over time. Again it’s important to consider endocarditis
to these patients. 20% of them will have a residual lesion and puts them at increased
risk for endocarditis. So in summary, ventricular septal defects
are very common. They’re common in isolation and they’re common with other lesions. They
present with increased blood flow to the left side of the heart with LV enlargement and
over time they can progress to pulmonary hypertension. The other summary points of VSDs are it’s
the size of the defect that determines the amount of increase left to right shunt. Defects
that are restrictive, it’s the size of the defect that determines it. Those that are
unrestrictive, it is the relative resistance of the two circulations that determines the
degree of shunt. They present with heart failure and failure to thrive, any signs of pulmonary
hypertension including accentuated S2 or cyanosis is very concerning and should warrant immediate
evaluation and consideration for surgical repair. Finally, imaging is best achieved via the
echo modality, x-ray, and EKG can be helpful in understanding pulmonary blood flow, and
the management of these patients centers around failure to thrive, therapies, and congestive
heart failure therapies, namely lasix and increased caloric density. Please help us improve the content by providing
us with some feedback.