Mitral valve disease

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Mitral valve disease


Cardiac tumors

Cardiac tumors




Mitral valve disease


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USMLE® Step 1 questions

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High Yield Notes

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Mitral valve disease

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USMLE® Step 1 style questions USMLE

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A 50-year-old woman comes to her primary care physician for evaluation of new onset shortness of breath and fatigue. She reports shortness of breath while lying flat, and she occasionally wakes up at night gasping for air. She also endorses an occasional productive cough with a “brown” tinge. Her medical history includes a “cardiac condition” in her youth that was treated with antibiotics. She immigrated to the United States from India at age 10. Temperature is 37.0°C (98.6°F), pulse is 100/min, respirations are 15/min, and blood pressure is 120/85 mmHg. ECG is obtained and demonstrated below. Cardiac auscultation will most likely demonstrate which of the following findings?

External References

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Mitral valve prolapse p. 298

fragile X syndrome p. 60

renal cyst disorders and p. 628


The mitral valve has two leaflets: the anterior leaflet and the posterior leaflet. Together, they separate the left atrium from the left ventricle. During systole the valve closes, which means blood cannot do anything but be ejected out of the aortic valve and into circulation.

If the mitral valve doesn’t completely shut, blood can leak back into the left atrium; this is called mitral valve regurgitation. During diastole, the mitral valve opens and lets blood fill into the ventricle. If the mitral valve doesn’t open enough, it gets harder to fill the left ventricle; this is called mitral valve stenosis.

Let’s start with mitral valve regurgitation. The leading cause of mitral valve regurgitation, and the most common of all valvular conditions, is mitral valve prolapse. When the left ventricle contracts during systole, a ton of pressure is generated so that the blood can be pumped out of the aortic valve; therefore, a lot of pressure pushes on that closed mitral valve. Normally, the papillary muscles and connective tissue, called chordae tendineae or heart strings, keep the valve from prolapsing, or falling back into the atrium.

With mitral valve prolapse, the connective tissue of the leaflets and surrounding tissue are weakened; this is called myxomatous degeneration. Why this happens isn’t well understood, but it is sometimes associated with connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome. Myxomatous degeneration results in a larger valve leaflet area and elongation of the chordae tendineae, which can sometimes rupture; this rupture typically happens to the chordae tendineae on the posterior leaflet, and can cause the posterior leaflet to fold up into the left atrium.

Patients with a mitral valve prolapse are usually asymptomatic, but often have a classic heart murmur that includes a mid-systolic click, which is sometimes followed by a systolic murmur.


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