Which feature best distinguishes the murmur of mitral stenosis from aortic stenosis in a 55-year-old woman presenting with dyspnea?
A. Radiation to the neck and right shoulder
B. Timing in diastole versus systole
C. Presence of an opening snap
D. Decreased intensity with Valsalva maneuver
Explanation
Distinguishing Mitral Stenosis from Aortic Stenosis
Key Point
The opening snap is a hallmark of mitral stenosis and is absent in aortic stenosis. This single finding reliably separates the two conditions.
Opening Snap in Mitral Stenosis
The opening snap occurs in early diastole when the stiff mitral valve abruptly opens under left atrial pressure. It is:
Heard best at the apex with the diaphragm
High-pitched and crisp
Followed by a low-pitched diastolic murmur (best heard with the bell)
Present only when the mitral valve is still mobile (not calcified or fibrotic)
Comparison Table: Mitral Stenosis vs Aortic Stenosis
Table
Feature
Mitral Stenosis
Aortic Stenosis
Timing
Diastolic
Systolic
Opening snap
Present (early diastole)
Absent
Best heard at
Apex
Right upper sternal border
Radiation
Axilla, not neck
Neck, right shoulder
Associated findings
Atrial fibrillation, RV heave
LV heave, slow carotid upstroke
Etiology
Rheumatic heart disease (India)
Degenerative, bicuspid valve
High-YieldNEET PG
The opening snap—not timing—is the single best discriminator because:
1.
Both conditions have murmurs in different phases (systolic vs diastolic), but timing alone does not distinguish them from other causes.
2.
The opening snap is pathognomonic for mitral stenosis when present and is never heard in aortic stenosis.
3.
It reflects valve mobility; its absence in calcified mitral stenosis indicates disease progression.
Clinical Pearl
In a young Indian woman with rheumatic heart disease, the presence of an opening snap + diastolic murmur at the apex = mitral stenosis until proven otherwise.
Why Other Options Fail
Timing (diastole vs systole): While mitral stenosis is diastolic and aortic stenosis is systolic, timing alone does not distinguish these from other diastolic (aortic regurgitation, pulmonary regurgitation) or systolic (mitral regurgitation, VSD) murmurs.
Radiation to neck: This is characteristic of aortic stenosis, not a discriminator—it confirms aortic stenosis but does not help distinguish it from mitral stenosis.
Valsalva response: Aortic stenosis murmur decreases with Valsalva (decreased preload → decreased flow). Mitral stenosis murmur also decreases. This is not a reliable discriminator.
Harrison 21e Ch 237
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