NBME 2 question help!!!

[shiv]

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A 72-year-old woman comes to the physician because of an episode of acute substernal chest pain that occurred while she was rushing to catch a bus. She has basilar crackles at both lung bases. S1 is normal and S2 is decreased. A grade 3/6 systolic murmur is heard best at the upper right sternal border and radiates to the neck. The following data obtained during cardiac catheterization were taken before and during exercise:


Left ventricular volume
Aortic pressure
(mm Hg) End-diastolic
(mL) End-systolic
(mL) Heart rate
(/min)
Control 130/70 140 50 85
Exercise 160/80 165 58 120

While exercising, the patient has shortness of breath but no chest pain. Which of the following is the most likely cause of the shortness of breath?

A) Decreased cardiac output during exercise

B) Decreased pulmonary blood flow

C) Increased aortic pressure

D) Increased end-diastolic pressure of the left ventricle during exercise

E) Tachycardia


I was thinkin it might be B because of crackles in her lung bases and lack of exchange of Oxygen..Or also i was thinking it could be dec. cardiac output during exercise...I kno its a systolic murmur so either aortic stenosis or mirtral regurgitation.. but with aortic stenosis resting BP would be high too. what do u guys think?

 

[deleted9493]

Sounds like a stenotic aortic valve to me. Concentric hypertrophy with increased LV pressures causing the pulmonary edema. If anything, her peripheral pressures are going to be low with said stenosis.

I would guess the diminished cardiac output answer to be the second best or more indirect answer of the two.

A 72-year-old woman comes to the physician because of an episode of acute substernal chest pain that occurred while she was rushing to catch a bus. She has basilar crackles at both lung bases. S1 is normal and S2 is decreased. A grade 3/6 systolic murmur is heard best at the upper right sternal border and radiates to the neck. The following data obtained during cardiac catheterization were taken before and during exercise:


Left ventricular volume
Aortic pressure
(mm Hg) End-diastolic
(mL) End-systolic
(mL) Heart rate
(/min)
Control 130/70 140 50 85
Exercise 160/80 165 58 120

While exercising, the patient has shortness of breath but no chest pain. Which of the following is the most likely cause of the shortness of breath?

A) Decreased cardiac output during exercise

B) Decreased pulmonary blood flow

C) Increased aortic pressure

D) Increased end-diastolic pressure of the left ventricle during exercise

E) Tachycardia


I was thinkin it might be B because of crackles in her lung bases and lack of exchange of Oxygen..Or also i was thinking it could be dec. cardiac output during exercise...I kno its a systolic murmur so either aortic stenosis or mirtral regurgitation.. but with aortic stenosis resting BP would be high too. what do u guys think?

 

[(nicedream)]

A 72-year-old woman comes to the physician because of an episode of acute substernal chest pain that occurred while she was rushing to catch a bus. She has basilar crackles at both lung bases. S1 is normal and S2 is decreased. A grade 3/6 systolic murmur is heard best at the upper right sternal border and radiates to the neck. The following data obtained during cardiac catheterization were taken before and during exercise:


Left ventricular volume
Aortic pressure
(mm Hg) End-diastolic
(mL) End-systolic
(mL) Heart rate
(/min)
Control 130/70 140 50 85
Exercise 160/80 165 58 120

While exercising, the patient has shortness of breath but no chest pain. Which of the following is the most likely cause of the shortness of breath?

A) Decreased cardiac output during exercise

B) Decreased pulmonary blood flow

C) Increased aortic pressure

D) Increased end-diastolic pressure of the left ventricle during exercise

E) Tachycardia


I was thinkin it might be B because of crackles in her lung bases and lack of exchange of Oxygen..Or also i was thinking it could be dec. cardiac output during exercise...I kno its a systolic murmur so either aortic stenosis or mirtral regurgitation.. but with aortic stenosis resting BP would be high too. what do u guys think?

I think it's C. She has aortic stenosis for sure, murmur at right sternal border radiating to neck is pathognomonic. Cardiac output seems okay, her ejection fraction is good (65%). That's my opinion.

 

[toehammer]

i think it's e. increasing heart rate during exercise increases the oxygen demand of the heart, and since there is stenosis it can't pump out enough to supply the coronaries producing substernal chest pain and sob.

 

[toehammer]

what does increased aortic pressure have to do with shortness of breath?

 

[(nicedream)]

what does increased aortic pressure have to do with shortness of breath?

Actually I was going by the acute substernal chest pain in the stem, indicating ischemia - I didn't read the sentence about sob without chest pain during exercise. I think this question is fuct.

 

[trudub]

I like D as an answer. The murmur is aortic stenosis. So, aortic pressure will not be elevated, it will be decreased. The stenosis reduces the cardiac output but that is not the cause of the shortness of breath. Because cardiac output is reduced, the end diastolic volume in the LV is increased and because of that the end diastolic pressure is also elevated. The elevated LVP transmits back into LA and then into the pulmonary circulation leading to elevated PCWP (indirect measurement of LAP) and pulmonary edema causing shortness of breath.

 

[shiv]

I think if she is tachychardic then she would have sob most of the time and exaggerated during exercise.. and this does not explain why she got crackles in her lungs. There is a backup from the left ventricle into the left atrium and causing fluid to build up in the lungs... what do u guys think?

 

[deleted9493]

I think if she is tachychardic then she would have sob most of the time and exaggerated during exercise.. and this does not explain why she got crackles in her lungs. There is a backup from the left ventricle into the left atrium and causing fluid to build up in the lungs... what do u guys think?

Elevated left ventricular pressure seems to be the most direct answer and I think you've got the right idea here.

A senile aortic valve does not cause elevated aortic pressures, rather, just the opposite. I don't think that a normal ejection fraction is necessarily incongruous with this finding...it just shows that she's still compensating with hypertrophy.

 

[(nicedream)]

Backups are usually with elevated ESV not EDV. You're right about the aortic stenosis/aortic pressure, I was thinking of systolic pressure in the ventricle, which would be elevated in aortic stenosis. Dunno.

 

[toehammer]

why are you saying she's tachycardic at rest, it says in the information she provided that she is not tachycardic at rest. its like 85? at exercise she is at 120. i think >100 is tachycardia.

 

[shiv]

i dont understand how tachychardia explains the crackles in lungs.. the way we can get crackles is due to the backup of fluid from heart.

 

[care bear]

i'm gonna go with E, or A, but i'd love some friendly arguments. learning is fun! 🙂

if answer choice D had read ESV and not EDV, i'd be right with you trudub.
but an elevated EDV in the left ventricle alone is not going to cause her problems, right?

also, i think it's important to read the format of the question carefully. . .to me, it is asking why she has dyspnea DURING EXERCISE. do we agree??

so i'm thinking the increased heart rate during exercise is leading to a further exacerbation of the elevated **ESV** that this woman has because of her stenotic aortic valve. . . caused by the heart rate. . .

actually, i've made my decision- i pick E, not A. because her ESV is increased during exercise but her overall CO (stroke vol x HR) is not neccesarily decreased.
the SOB during exercise is most directly related to the tachycardia, which her poor heart valve just can't deal with like most folks can.

argue away!

 

[shiv]

I would go with E but how do u explain the crackles with tachychardia? i kno that if a person is tachychardic he/she is getting less amount of blood in the coronary artery with every heart beat and eventually its gonna lead to ischemia. She is only getting SOB when doing anything physical like running or exercising which shows that not enough blood is going to the heart and the systolic murmur further verifies it to be a stenotic valve. Now if a valve is stenotic the EDV is gonna increase which will lead to back pressure into your atrium and eventually to your lungs causing edema, and hence the crackles.. Wat do u guys think?

 

[care bear]

never mind. i think answer D is right after looking it up!!

i guess was thinking that the SOB was mainly due to an increased ESV, not an increased EDV in the left ventricle. so i was looking for the answer that supported that idea.

but never mind; i am now pretty positive that D is right.

 

[JaniceDickinson]

D--incrs EDV of LV during exercised

"everything gets backed up theory"
incrs in EDV of LV --> fluid backed up into LA --> into pulmonary veins --> incrs in capillary hydrostatic pressure (Starling's forces) --> incrs fluid in interstitial space --> edema (this would explain lung crackles) --> SOB

 

[Idiopathic]

but with aortic stenosis resting BP would be high too.

Id like to know why you think resting BP has to be elevated in AS.

I think the answer has to be D. Increased venous return to a heart that cant get blood out as well and you increase pulmonary vein pressure due to increased LVEDP/V. This in turn backs up the lungs and its the same physiological mechanism as being 'wet'. The AS is apparently reasonably well compensated for as long as the patient is not exercising, and CO should be reasonably able to allow for cardiac perfusion (so far), but remember that a normal heart CO goes way UP during exercise, hers likely only goes up slightly.

And we all get tachycardic when we exercise, this likely has very little to do with the disease process.

 

[bolisol007]

Idiopathic (or anyone else that can help),
wouldn't "fluid back-up in the lung" be the same thing as "decreased pulm. flow"? In other words, why is option B wrong?

Id like to know why you think resting BP has to be elevated in AS.

I think the answer has to be D. Increased venous return to a heart that cant get blood out as well and you increase pulmonary vein pressure due to increased LVEDP/V. This in turn backs up the lungs and its the same physiological mechanism as being 'wet'. The AS is apparently reasonably well compensated for as long as the patient is not exercising, and CO should be reasonably able to allow for cardiac perfusion (so far), but remember that a normal heart CO goes way UP during exercise, hers likely only goes up slightly.

And we all get tachycardic when we exercise, this likely has very little to do with the disease process.

 

[Idiopathic]

CO actually increases in this womans heart, due to exercise, and CO of right heart has to equal CO of left heart. Pulmonary blood flow increases, but so do the pressures, and the 'backing up' of fluid really causes underventilated lung to be overperfused, creating an intrinsic V/Q mismatch. I think she gets 'crackles' due to increased pressures causing leaky capillaries and fluid edema, but I think she gets SOB due to the mismatch and underventilation relative to perfusion.

 

[bolisol007]

Thanks, that helps!

CO actually increases in this womans heart, due to exercise, and CO of right heart has to equal CO of left heart. Pulmonary blood flow increases, but so do the pressures, and the 'backing up' of fluid really causes underventilated lung to be overperfused, creating an intrinsic V/Q mismatch. I think she gets 'crackles' due to increased pressures causing leaky capillaries and fluid edema, but I think she gets SOB due to the mismatch and underventilation relative to perfusion.

 

[shiv]

idiopathic
i actually miswrote that .. In aortic stenosis resting BP is not high..thas more with aortic regurgitation when u have hyperdynamic pulses..more blood regurgation back and more stroke volume pushed out hence the high pressure..