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Old 09-22-2010
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Stethoscope The cause of this third heart sound?

A 54-year-old woman presents with a pansystolic murmur along the lower left sternal border radiating rightward to the midclavicular line. The murmur is medium pitched, has a blowing quality, and increases slightly on inspiration. An S3 is audible along the lower left sternal border. Jugular venous pressure is elevated, and a prominent "v" wave is visible. Which of the following is the most likely etiology of the S3?

A. Aortic stenosis
B. Mitral regurgitation
C. Pulmonic stenosis
D. Tricuspid regurgitation
E. Volume overloaded left ventricle
F. Volume overloaded right ventricle

Requesting the people who post answers to give the reasoning, especially when two or more answers who seem close need differentiation.
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Old 09-22-2010
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There are only 3 causes for a pansystolic murmur; VSD, MR, TR.

Only the murmur of TR would increase on inspiration (due to increased VR). However, the answer here would be:

F. Volume overloaded right ventricle

TR would cause overloading of the right ventricle with blood, producing an S3 sound. It would also cause jugular distension. S3 is pathognomonic for volume overload. It results from splashing of blood against the dilated flabby ventricle. It also signifies ventricular failure.
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Old 09-22-2010
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Yup - I agree.

S3s are due to volume overload.

This is a pansystolic murmur in the Tricuspid area (lower left sternal border.) That means regurgitation and volume overload.

Put the two together and you have a volume overload in the right heart.
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Old 09-22-2010
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ive read before on uworld that an increased amount of blood flow going through the tricuspid/mitral valve without an already full left ventricle can also create an S3 (as would be present in a tricuspid/mitral valve regurgitation) but i still would go for F =)
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Old 09-22-2010
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In additioin I would like to add that this pansystolic murmur is not due to organic pathology of tricuspid, but due to increased volume of blood in the right ventricle which is splushed back into right ventricle due to overload. This kind of murmur is called FANCTIONAL MURMUR.

Am I right?
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Old 09-22-2010
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Ya right. its called functional murmar. ans is F.
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Old 09-23-2010
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No more question takers???
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Old 09-23-2010
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Quote:
Originally Posted by donofitaly View Post
No more question takers???
Waiting for the answer now
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Old 09-23-2010
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The correct answer is F.

The origin and radiation of the pansystolic murmur suggest tricuspid valve
incompetence. This is further supported by its pitch and quality, and by the fact that it increases on inspiration when cardiac volume increases. The regurgitant blood flow from the ventricle during systole increases jugular
venous blood pressure and atrial v wave amplitude. The origin of the S3 sound, which occurs during early rapid filling, is the filling of a volume-overloaded right ventricle. The right ventricle overload is caused by the
combination of systemic venous return and the return of the regurgitated blood volume into the right ventricle. Right ventricular failure and dilatation, with enlargement of the tricuspid valve orifice, is the most common cause
of tricuspid regurgitation and is often secondary to pulmonary hypertension or left ventricular failure.

Aortic stenosis (choice A) causes a harsh, shrill, midsystolic, crescendo-decrescendo murmur and would not necessarily elevate right heart (and so jugular venous) pressures. It is often associated with an S4 (late rapid
filling) rather than an S3.

Mitral regurgitation (choice B) causes a soft, blowing, pansystolic murmur and is associated with an S3. It would elevate left atrial pressures, not right atrial (and so jugular venous) pressures.

Pulmonic stenosis (choice C) would also cause a crescendo-decrescendo murmur, not an S3.

Tricuspid regurgitation (choice D) is the source of the murmur but not the source of the S3 sound.

A volume-overloaded left ventricle (choice E) could cause an S3, but tricuspid regurgitation will not cause a volume overload in the left ventricle.

Well done to the people who got the answer and the reason right.
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