Alright, guys. We have an absolutely high-yield and important question,
you will see this diagnosis on your boards and it’s important. Let’s jump right in.
A 59-year-old male with a history of aortic stenosis secondary to a bicuspid aortic valve
treated with aortic valve replacement presents with fever and shortness of breath.
The patient states a gradual onset of symptoms approximately 5 days ago that had been getting steadily worse.
He reports that he has trouble getting up and walking across the room before becoming short of breath.
Past medical history is significant for a mechanical aortic valve replacement three years ago for severe aortic stenosis.
He also had removal of a benign polyp last year following a colonoscopy and a tooth extraction two weeks ago.
Current medications are Warfarin 5 mg orally daily, rosuvastatin 20 mg orally daily, and enalapril 10 mg orally twice a day.
On physical examination the patient is alert but dyspneic and also has small red nodules on the palms of his hands.
Cardiac exam is significant for a systolic injection murmur
that is loudest at the upper right sternal border and radiates to the carotids.
Lungs are clear to auscultation.
The abdomen is soft and nontender, splenomegally is present.
Extremities are pale and cool to the touch. Laboratory results are significant for a leukocytosis.
Patient has a chest X-ray that shows no evidence of dehiscence or damage to the mechanical valve.
A transesophageal echocardiogram shows a possible large vegetation on the mechanical aortic valve leaflets.
The left ventricular ejection fraction is 45% due to outflow tract obstruction.
High flow supplemental oxygen and fluid resuscitation are started. Blood cultures times two are drawn.
What is the next best step in management?
Answer choice A: Stop Warfarin immediately;
Answer choice B: Administer vancomycin 1 gm IV every 12 hours,
gentamicin 70 mg IV every 8 hours, and rifampin 300 mg IV every 8 hours;
Answer choice C: Emergency replacement of the mechanical aortic valve;
Answer choice D: Administer dobutamine; or
Answer choice E: Intra-aortic balloon counterpulsation.
Now take a moment to come to the answer by yourself before we go through it together.
Okay, guys, like I was saying this is a very important question.
The topic we are going to discuss here and some of the fine detail are absolutely going to be on your boards.
You may even see it a handful of times. This topic is that important, so let’s focus.
Now for question characteristics this is actually a surgery question.
We're dealing with someone who had a aortic valve replacement of the heart,
is found to be having some kind of medical problem in that setting, so it falls under surgery.
Now this is a two-step question.
The first thing we have to do is determine the diagnosis and then the next best step in management.
And of course here the stem is required because we need to filter out the question stem
and sift through it to come to the appropriate diagnosis.
Now let’s go through this question.
The first thing like we said, we gotta figure out the diagnosis.
We have a 59-year-old patient coming to us and they're coming with the chief complaint of fever and shortness of breath.
We're told that he even has shortness of breath when walking across the room.
Now, that’s your New York Heart Association Stage III symptoms and he even had shortness of breath due to mild activity.
Now we're told the onset is gradual and it started five days ago
so really our differential here is prompted by the symptomatology of what we're hearing.
Now the patient having fever, that can be due to infection or inflammation
so we need to look to see if there's a entry potential of an infectious agent in the clinical vignette.
Also on our differential is that well he has shortness of breath, well that could be due to his lungs?
Let’s say if he has pneumonia or it could be due to his heart if he has congestive heart failure.
So again, we have to look more in our vignette to try to see which organ is likely involved.
Now we're told he had a recent tooth extraction.
Now as a general rule, whenever you see something like this on a USMLE test, they’re probably telling you for a reason.
So tooth extractions are always mentioned on USMLE exams because sometimes dentist will hold anticoagulation
or in this case a tooth extraction can actually be a potential entry route for infectious agent
because the infectious agent can enter into the blood stream during the tooth extraction procedure.
Now, the medical history is significant for an underlying heart condition.
We were told that he had the aortic valve replacement
so shortness of breath being due to the lungs is a bit less likely and then more likely due to the heart.
Now a prosthetic aortic valve is actually a risk factor for endocarditis
because vegetation can actually form more easily on a prosthetic valve than a natural one.
Now endocarditis of the aortic valve could be confirmed in this setting by looking at the clinical exam
they talk about and some paraclinical test.
Now, we’re told essentially that the patient has small red nodules on the palms of his hands, those are called Janeway lesion.
We’re told he has a systolic ejection murmur that radiates to the carotids
but that’s supported by the fact that on transesophageal echo he has a large valve vegetation
and he has a reduced ejection fraction which can be seen in endocarditis and he has splenomegaly
which is nonspecific in general but it is consistent with endocarditis.
So this patient’s diagnosis is endocarditis, but more specifically, it’s prosthetic valve endocarditis.
So given the fact that he has prosthetic valve endocarditis the question becomes, what’s the next best step in management?
And I say the word best like that, maybe even a little bit annoyingly
because I want to get it into your head, even if it bothers you a bit, that’s okay because I want you to always remember,
read the last sentence of these questions outrageously carefully.
A lot of the answers that they're mentioning in the answer choices are completely valid
but they’re valid in different situations and some are absolutely not the best and obviously one is the best,
so I really want you to key in on that.
Think to yourself, what’s the next best step of management not what is a viable answer.
USMLE doesn’t care about viability, they care about the best answer so let’s do that right now.
First thing we need to do is say, okay, this guy has endocarditis.
Now we know the definitive diagnosis of endocarditis is made of via what is called the modified Duke criteria
and we’ll take about that shortly, and when we go through the high-yield facts,
but for now, let’s go to the answer choices to see how you can pick the right one.
Now, looking at answer choice A, we’re told that, you know, they're saying you wanna stop Warfarin,
answer choice B they are giving antibiotics, answer choice C, they're doing surgery,
answer choice D they are giving a medication and answer choice E they’re doing a procedure.
The nice thing here is that all the answer choices are really different in the style of intervention.
Some have to do with withholding medication, some are giving medication, some are surgery,
some are doing a procedure, so that kinda help, so let’s think on that big level to help us narrow down our thinking.
Now, if you realize they are telling that they are giving fluids and they are giving oxygen
so stabilization measures are already taken.
Now, surgery is a potential necessity given the extent of the valve damage that’s described
but the patient is hemodynamically stable and we’re not gonna do that now and the infectious agent here really isn't known.
We said blood cultures but we don’t know what they’ve come back yet so you know what we want to do then is start empiric therapy.
We have a guy he’s got an infection, it’s endocarditis from a prosthetic valve, he’s got a fever.
We’re already giving him fluids so the next best step is, will he stable?
So we don’t need to rush him to the OR, we don’t need to do a sudden procedure,
we just need to set him up to make sure he’s stable so antibiotics will buy us time
until we figure out what’s the causative agent and then seeing on further workup what he needs,
and that is because the patient is hemodynamically stable, that’s outrageously important.
So let’s go through some of the answer choices in a bit more detail.
Now like we said, the patient present with signs and symptoms of prosthetic valve endocarditis
because he has fever, he has a systolic ejection murmur, he has leukocytosis,
he has splenomegally, and he had a recent dental surgery.
Now, the diagnosis in this case was confirmed
because they did a transesophageal echo and they saw the vegetation and he also has secondary heart failure.
Now, the next best step like we said, is to begin immediate empiric antibiotic therapy
with vancomycin, gentamicin, or rifampin while we wait for the blood cultures to comeback.
Now, looking at the other answer choices, answer choice A, is stopping Warfarin immediately.
Now -- okay, anticoagulation, think about it,
is recommended for patients who have these prosthetic valves because it reduces the thromboembolic risks.
Now, you would want to reverse or stop therapy if there was a concern for an intracranial or intracerebral hemorrhage
or there was an impending surgery for which you would stop anticoagulation,
but this patient it’s not necessary because there’s no evidence in the question stem of him having an intracerebral hemorrhage
and surgery’s not indicated currently because he’s hemodynamically stable,
so you don’t want to run and stop someone on anti-coagulation if you’re not going to the OR right away
because then you’re gonna put him on a risk for sending up thromboemboli.
Answer choice C which is the emergency replacement of the mechanical aortic valve.
Now, indications for a valve replacement or if you have moderate to severe heart failure on presentation
especially if it doesn’t get better with medical management or after you’ve had a surgery,
if you have evidence of dehiscence or instability of the valve on imaging.
Now in this case the heart failure is moderate but the patient’s hemodynamically stable
and there’s no evidence of valve failure so at this time we don’t need to do surgery.
Now answer choice D involves dobutamine which is a positive inotrope
that can be used to increase cardiac output without significantly increasing myocardial oxygen demand.
Now this patient he’s mildly hypotensive, he has a reduced TF and he could benefit from dobutamine therapy
but again he’s hemodynamically stable and so we don’t need to do that currently,
it could be a viable option, this is definitely a distractor, but picking antibiotics takes precedent over this,
he’s already hemodynamically stable. If they had worded the question that he was unstable,
then you may -- this would probably be the right answer because stability wins over starting antibiotics,
but since he’s stable, antibiotics win over dobutamine.
Now answer choice E, intra-aortic balloon counterpulsation, this can be useful in causes of acute mitral regurgitation
and that’s when you would want to put this on surgery as not available and hemodynamic stabilization is needed,
but putting in intra-aortic balloon counterpulsation is contraindicated in the presence of an incompetent aortic valve,
so it would definitely not be useful for this patient.
Now let’s go over some high-yield facts. For endocarditis, bacterial or fungal vegetations are going to be on the heart valves.
Of course, bacterial is much more common and streptococcus and staphylococcus are the most common agents.
Now you can have variable clinical manifestations of endocarditis this includes fever, fatigue,
shortness of breath, chest pain, edema, a heart murmur or skin lesions.
Now, the risk factors for getting endocarditis or IV drugs use, a very big buzz word on the USMLE questions
and in this case if you have someone who use -- had IV drug use -- tricuspid valve is generally affected
due to the venous inflows since IV drugs are injected into veins.
You can also have endocarditis due to damage heart valves or prosthetic heart valves.
Now the diagnosis of endocarditis is really paced on what’s called the Modified Duke Criteria.
Now let’s look at that now.
So for the Modified Duke Criteria for infective endocarditis they were what are called
Major criteria and there are what are called Minor criteria.
The Major criteria are as follows.
The first of the major criteria is two blood cultures positive for infective endocarditis
and the second major criteria is evidence of endocardial involvement.
Now the minor criteria, there’s five of them.
These include one, having a predisposing factor that would be having IV drug use or some type of underlying heart condition.
Second would be a fever or temperature greater than 38.0 degrees Celsius.
Third is what is called the vascular phenomenon and that could be arterial emboli, septic emboli,
pulmonary infarcts, or painless skin lesions called Janeway lesions.
Four is going to be immunological phenomenon.
Now this can be glomerulonephritis, painful nodules called Osler’s nodes or retinal hemorrhages called the Roth spots.
And five is going to be microbiological evidence which is going to be either a single positive blood culture
or serological evidence of infectious agent causing endocarditis.
Now to have a definitive diagnosis you need two major criteria or one major criteria and three minor
or all five minor and then possible diagnosis is going to be one major and one minor or three minor criteria.