Okay, guys, we have a really complex question here.
Put on your thinking caps, you will see questions like this on the boards, let's dive right in.
We have a six-week-old female infant who is brought to a pediatrician due to feeding difficulty for the last four days.
Her mother mentions that the infant is breathing rapidly and sweating profusely while nursing.
She has been drinking very little breast milk and stopped feeding as if she is tired only to start sucking again after a few minutes.
There is no history of cough, sneezing, nasal congestion, or fever.
She was born at full term and her birth weight was 3.2 kilos or seven pounds.
Her temperature is 37°C, pulse is 190 and respiratory rate is 64.
On chest auscultation, bilateral wheezing is present.
There is a precordial murmur which starts immediately after the onset of the first heart sound, S1,
reaches its maximal intensity at the end of systole and wanes during late diastole.
The murmur is best heard over the second left intercostal space and radiates to the left clavicle.
The first heart sound, S1, is normal while the second heart sound, S2, is obscured by the murmur.
Which of the following is the most likely diagnosis?
Answer choice A: Aortopulmonary window.
Answer choice B: Congenital mitral insufficiency.
Answer choice C: Patent ductus arteriosus.
Answer choice D: Supracristal ventricular septal defect with aortic regurgitation, or
Answer choice E: Ruptured congenital sinus of Valsalva aneurysm.
Now take a moment to come to your own answer choice before we go through it together.
Okay, like I warned in the beginning, we’re gonna need our thinking caps
but the reality is USMLE loves this question so we gotta get good at them
and that’s what we’re gonna do right now.
So, the question characteristics, this is a pediatric question.
We have a six month, excuse me, six week female infant coming in to the pediatrician with several complaints, so this is pediatrics.
This is a one step question, they just want us to figure out the diagnosis.
How nice of them, but wow, this is a hard diagnosis to come through, so don’t get tricked by this one-step questions,
they can definitely be hard and the stem is absolutely required as we have to take a lot of information from the question stem,
filter through it and make sense of it to come to the correct diagnosis.
Now, what we’re told here is that we have a six week old infant and the chief complaint is feeding difficulty.
We’re told that it’s recent onset and it started only four days ago.
Now, the feeding difficulty presents as being associated with tachypnea, sweating, fatigue and recovery after several minutes.
Now here we have a wide differential diagnosis for feeding difficulties.
This can be a under developed GI system, trauma during birth
but kind of unlikely given that we’re told she had a uneventful full term birth
or it can be due to respiratory disease and cardiac disease.
Well, when we looked at the answer choices we see that they are all related to heart and cardiovascular disease
and we’re told of a significant auscultation abnormality,
so, really, our brain here is all focused on cardiovascular and heart abnormalities.
Now, the real task to this question is identifying the murmur that they are talking about.
Now, we’re told there is a precordial murmur which starts immediately after the onset of the first heart sound
reaches its maximal intensity at the end of systole and wanes during late diastole.
Well, that sounds really fancy but here’s the irony -
all they’re doing is using really fancy words to describe a crescendo-decrescendo murmur.
Now you may be thinking, wow, that does sound like that.
They are saying the heart sounds is immediately after S1,
get’s maximal intensity at the end of systole and then wanes during late diastole.
That is crescendo-decrescendo.
In the old days of USMLE, people will just look for buzz words like crescendo-decrescendo
but the world of USMLE has changed and so now, they describe things in complex ways so you can’t just rely on buzz words
and that’s why this question is so important.
We want you to get used to the idea of reading different words and then understanding
what’s going on rather than simply searching for buzz words.
This strategy that we’re teaching is how you’re going to kill the USMLE exam.
Now, so we know it’s a crescendo-decrescendo and they tell us it’s best heard over the left second intercostal space
which is the auscultation location of course of the pulmonary artery and we’re told its radiates to the left clavicle.
Now, if you take all of that, this murmur characteristic is characteristic of a patent ductus arteriosus
which is Answer choice C which is the correct answer.
Now let’s quickly talk about some of the other answer choices and what we’ll expect for their murmurs.
Now, Answer choice A talks about having a aortal pulmonary window.
Now this causes a similar murmur to a patent ductus arteriosus
but it’s heard in the upper left parasternal area as the left to right shunt is in anatomically inferior location than a PDA.
Now, another answer choice here is congenital mitral insufficiency, Answer choice B.
Now, mitral insufficiency or regurge causes a holosystolic murmur that is in constant intensity, not what we’re seeing here.
Now, Answer choice D which is supercristal ventricular septal defect
with aortic regurgitation causes a holosystolic murmur of constant intensity,
that’s the ventricular septal defect component, and then you have a decrescendo diastolic murmur which is the aortic regurgitation.
Again, not what were being described in the question stem.
And you have Answer choice E, which is a ruptured congenital sinus of Valsalva aneurysm -
now this causes a similar murmur to a PDA but genuinely it’s more attenuated in diastole and heard at the lower external boarder.
Now, that’s a quick overview of some of the other murmurs, let’s talk about the same ones in a little bit more detail.
I'm giving you multiple run throughs because it takes some time to breath all this in and feel them to really understand your murmurs well.
Now, we're looking at our correct answer choice which is Answer choice C,
we know its patent ductus arteriosus, so let’s talk about PDAs.
Now, normally, the ductus arteriosus closes functionally soon after birth.
If it remains patent after the fall of pulmonary vascular resistance in an infant,
then you have a left to right shunt of blood from the aorta to the pulmonary artery.
Now children with a small PDA are usually asymptomatic and the condition is diagnosed only
when a murmur is detected on auscultation.
Now patients with larger PDAs may present during infancy with clinical features of heart failure
and they can have difficulty such as feeding difficulties -- suck, rest, suck cycle feeding;
excessive perspiration; wheezing and growth failure.
Many of these we saw in the questions stem for this patient.
Now, the auscultation of the precordium will reveal the classic murmur associated with the PDA
and that was described in our question stem.
Now, the murmur has a machinery like continuous characteristic and it starts immediately after the first heart sound,
it reaches maximal intensity at the end of systole and wanes during diastole, that’s the crescendo-decrescendo component
and it is best heard in the second left intercostal space and it can radiate to the left clavicle or down the left sternal boarder.
Now in this case, the first heart sound is normal and the second heart sound is usually obscured by the murmur.
Now, with the development of pulmonary hypertension, over time the diastolic component of the murmur
will actually disappear and if there is a large left to right shunt, a mid diastolic low pitch rumble
is actually heard over the apex due to increase blood flow across the mitral valve.
Now the murmur here with the PDA is usually accompanied by a thrill,
which is a maximal in the second left intercostal space and it can again radiate to the left clavicle.
Now, down the left sternal boarder or even to the apex,
so you really have quite a wide variety of where your radiation of the thrill can occur.
Now, usually this thrill is systolic but it can actually be palpated during systole or diastole.
Now another important clinical sign of a large PDA is the presence, now this is important,
of a bounding peripheral pulses and a wide pulse pressure and here the sign occurs
because of the rapid run off of blood into the pulmonary artery during diastole.
Now let’s go back to Answer choice A, the aortopulmonary window.
Now, this is characterized by the presence of a communication between the ascending aorta and the main pulmonary artery.
In a large defect, a systolic murmur is present along with a mid-diastolic apec rumble.
Now, in a smaller defect, a continuous murmur is present, similar to that heard in the PDA
but the murmur is best heard at the left upper external boarder.
Now let’s look at Answer choice B.
This is a congenital mitral insufficiency and that’s going to be characterized by a high pitch holosystolic murmur
which is best heard at the cardiac apex.
Now, a mid-diastolic rumble may also be present in a moderate to severe mitral insufficiency.
Now, looking at Answer choice D, a supracristal ventricular septal defect with aortic regurgitation.
Now, this may sound really esoteric, but this is where the USMLE boards are going -
they want you to be able to identify different pieces of murmur and piece together a diagnosis.
Now, in a supercristal ventricular septal defect aortic regurgitation usually this will happen in someone
who is between 5 to 9 years of your age so not relevant in this case.
Now the murmur is due to a supracristal ventricular septal defect is actually holosystolic
and it’s best heard at the mid to upper left external boarder.
If aortic regurgitation is present, then you will also have a decrescendo diastolic murmur
that’s best heard at the upper right or mid-left sternal boarder.
Now, Answer choice E, a ruptured congenital sinus of Valsalva aneurysm can be congenital.
It usually actually presents during puberty or adulthood and again based on age, we can eliminate this one.
On auscultation, we will have a loud continuous murmur is present if the sinus of Valsalva aneurysm
actually ruptured and it is more defused than a PDA and maybe attenuated during diastole.
Now, let’s review some high yield facts for a patent ductus arteriosus.
Now a PDA is a persistent connection between the aorta and pulmonary artery beyond birth.
It’s caused by a failure of the ductus arteriosus to close and this leads to a left-to-right shunt with overload of the pulmonary circulation.
Now, if you look at the image below, you can see the high pressure of the aorta going into the pulmonary artery
via the patent ductus arteriosus will cause a overload of that pulmonary circulation.
Now, often, this PDAs can be asymptomatic when they are small but signs and symptoms of the PDA
really depend on the size and the larger, the more symptoms you have
and the symptoms can involve difficult breathing, wheezing on auscultation -
that’s due to fluid congestion in the lungs, feeding difficulties and of course the characteristic heart murmur we already described.
Now the diagnosis here of course you can catch it on auscultation but to be able to really diagnose it,
you do a Doppler echo cardiogram of the heart and see the flow between the aorta and pulmonary artery.
Now, treatment here for this PDA is really depends on the size and symptoms of the patient.
If it’s small and mild, you can do outpatient monitoring.
Now, you can also give NSAIDS and really here a prostaglandin e2 is involved in keeping the PDA open,
so that’s actually a good target and the rationale here is once someone has a PDA,
their heart and system adjusts to the PDA so you don’t want it to close on its own cuz that can be traumatic,
so you can give this NSAIDS to keep it open while you buy time to come up with a more appropriate treatment strategy
which can often include closure through percutaneous intervention.