Clinical Presentation of Congenital Heart Disease in the First Week of Life: Congestive
Heart Failure, by Dr. Michael Freed.
My name is Michael Freed and I'm a Pediatric Cardiologist at Boston Children's Hospital
and at Harvard Medical School.
And I want to spend a little time today talking about congenital heart disease in the newborn
period.
Introduction.
Children come in in the first week of life.
They present in one of four ways.
With a heart murmur, with an arrhythmia, congestive heart failure, or with cyanosis.
So let's talk about congestive heart failure.
Congestive heart failure is an inability of the heart to do the work that's required,
and the signs and symptoms that come because of that inability.
There are two conceptual reasons why you might have difficulty.
The first is that there is something wrong with the heart muscle.
You have a normal amount of work.
But somehow the muscle just isn't strong enough to do the work.
The second is that you have a normal muscle, but you've put too much of a workload on it.
So if there was a weight on the table in front of me, if there was a 5 pound weight and I
couldn't do it, there's something wrong with me.
If there's 1,000 pound weight, I just can't do a 1,000 pound weight.
If you looked around our ward, I think you would say that the structural problem, too
much work with normal muscle is much more common.
I'm not so sure that's the case.
Fetal Development.
I think that almost all of these are genetic defects.
And I suspect there are just as many genetic defects in the mitochondria and energy transport
systems as there are causing structural heart disease, but we just don't see them.
Where are they?
Well, I think they don't survive fetal life.
I think that you can be born without kidneys, you can be born without lungs, you can be
born without a large part of your brain.
But once you have an embryo that's more than four cells thick, you need some way of getting
nutrients inside to the cells and get waste products out.
So once an embryo is more than four cells thick, you need some type of circulatory system.
And in fact, in the human, there's a primitive straight tube that develops by 27 days after
conception that's actually doing the work.
And if there's something wrong with that tube, if there's something wrong with the muscle,
they just don't survive fetal life.
So I think a lot of first trimester abortions may very well be heart muscle problems that
we're not seeing.
And the rest of fetal life selects out for those, leaving just the ones with normal muscles,
but structural problems.
And the corollary to that is that the things that we're seeing at birth are in fact things
that work in utero.
Otherwise, they wouldn't survive fetal life.
And what happens is that I think that the fact that the circulation is arranged in parallel
rather than series allows a whole group of very complicated diseases that work in the
newborn period, but once you go into that in the series circulation, don't work after
you're born.
So I think this presentation of babies in the first week of life are kids that worked
in utero, but don't work when they're born.
And I think there's a comparable group that doesn't work in utero that we're not seeing,
and a lot of those have muscle problems.
Structural Heart Disease.
So if we have a baby with congestive heart failure-- he doesn't have a muscle problem,
he's got some structural problem, too much work for a normal muscle.
And remember, we said the work of the heart is pressure and volume, so there must be either
too much pressure work or too much volume work.
If you look at the first month of life, I think that most kids who come in would be
too much volume work.
Ventricular septal defects, single ventricles without pulmonary stenosis, truncus arteriosus,
the whole variety of things.
But we don't see those in the first week of life.
In the first week of life the pulmonary vascular resistance is still quite high.
And it prevents enough of a left-to-right shunt through the VSD, or the single ventricle,
or the truncus to give enough of a volume overload to cause congestive heart failure.
So if our talk is heart failure in the first week of life, which is what we've started
the premise, then we're dealing not with muscle disease, not with volume overload, but just
pressure overload lesions.
And if you look at the pressure overload lesions, aortic stenosis, pulmonary stenosis, coarctation,
and hypoplastic left heart syndrome.
And I'm going to make it even easier.
Pulmonary stenosis doesn't fit here.
If we're talking about heart failure, tachypnea, tachycardia, not feeding very well, sweating--
that's not the way pulmonary stenosis presents.
If you look at pulmonary stenosis, these kids have severe right ventricular outflow tract
obstruction.
The right ventricle has to generate a higher pressure to pump blood out.
And if it starts having difficulty generating that higher pressure, by Starling's Law, it
increases preload.
If you increase the preload in the ventricle, the atrial pressure goes up.
And in the newborn period, if the right atrial pressure exceeds the left atrial pressure,
you start shunting right-to-left and you end up with cyanosis.
So kids with severe right ventricular outflow tract obstruction from pulmonary stenosis
present with cyanosis, not with congestive heart failure.
So now we're essentially down to three diseases in our differential diagnosis of heart failure
in the newborn period.
And how can we tell these apart?
Well, coarctation-- now, the difference in pulses or blood pressure should work.
That is, before the ductus closes they're not sick.
But if these kids are sick, the ductus must have closed and now they must have a pressure
gradient.
So just feeling pulses or measuring pre- and post-ductal blood pressures should diagnose
coarctation for you.
In neonates with coarctation of the aorta, the strength of the pulses in the lower extremity
will be reduced or absent in comparison to the pulses in the upper extremity.
Pre- and post-ductal blood pressure examination will reveal a discrepancy between the right
arm-- which is pre-ductal-- and the leg-- which is post-ductal-- blood pressures, with
a higher systolic blood pressure in the right arm when compared to the legs.
Typically, a discrepancy of greater than 20 millimeters of mercury in the systolic pressure
measurement is considered significant and should prompt further workup for coarctation.
To separate out aortic stenosis from hypoplastic left heart syndrome get an electrocardiogram.
These kids have LVH.
These kids have no LV.
And that's the differential diagnosis of heart failure in the newborn.
This concludes our video on Clinical Presentation of Congenital Heart Disease in the First Week
of Life: Congestive Heart Failure.
Thank you.
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