Why is S1 soft in Mitrial Regurgitation
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"mitral regurgitation" AND "heart sounds"
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mitral regurgitation soft S1 mechanism first heart sound
S1 is soft in mitral regurgitation because the mitral valve does not close sharply and effectively at the start of systole.
Normally, S1 is produced mainly by abrupt closure and tensing of the mitral and tricuspid valves. In significant MR:
- The mitral leaflets may be structurally abnormal or fail to coapt properly.
- Blood begins leaking from the LV to the LA as soon as systole begins.
- This reduces or eliminates the normal isovolumetric contraction phase, during which LV pressure rises rapidly against closed valves.
- Therefore, there is less abrupt valve tensing and vibration, giving a soft S1.
- The holosystolic murmur can also partly mask S1.
This is most typical of severe or chronic MR. S1 can occasionally be normal depending on the valve pathology and severity. Clinical Methods describes reduced S1 in holosystolic MR due to the absent isovolumetric period, blunted LV pressure rise, and masking by the murmur.
Pressure in aorta during iso volumetric contraction
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"isovolumetric contraction" AND aortic pressure
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aortic pressure during isovolumetric contraction aortic valve closed physiology
During isovolumetric contraction, the aortic pressure is still the diastolic aortic pressure, approximately 80 mmHg in a normal 120/80 mmHg arterial pressure.
- Mitral valve closes when LV pressure just exceeds left atrial pressure.
- Both mitral and aortic valves are then closed.
- LV pressure rises rapidly, but aortic pressure does not rise yet because no blood has entered the aorta.
- When LV pressure exceeds aortic pressure (about 80 mmHg), the aortic valve opens and ventricular ejection begins.
So: aortic pressure remains nearly constant at its diastolic level during isovolumetric contraction, while LV pressure rises from about 5-10 mmHg to >80 mmHg.
If the patient has LV-Aorta gradient of 40mmhg, peak velocity across valve: 4 m/s and area of valve: 1 cmsq. Will this patient meet criteria for severe Aortic Stenosis
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"aortic stenosis" AND echocardiography
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2025 guideline severe aortic stenosis peak velocity 4 m/s mean gradient 40 valve area 1.0 cm2
Yes, this is severe aortic stenosis by echocardiographic criteria, based on:
| Parameter | Given | Severe-AS threshold | Interpretation |
|---|---|---|---|
| Peak aortic jet velocity, Vmax | 4.0 m/s | ≥4.0 m/s | Severe |
| Aortic valve area | 1.0 cm² | ≤1.0 cm² | Severe threshold / borderline |
| Mean transvalvular gradient | 40 mmHg, if this is the mean Doppler gradient | ≥40 mmHg | Severe |
The standard severe-AS cutoffs are Vmax ≥4.0 m/s, mean gradient ≥40 mmHg, and AVA ≤1.0 cm², as summarized in the ESC criteria.
Important nuance: “LV-aortic gradient of 40 mmHg” must be specified.
- If it means the mean Doppler gradient, it meets severe-AS criteria.
- If it is a catheter peak-to-peak LV-aortic gradient, it is not interchangeable with the Doppler mean gradient, so it should not be compared directly with the 40-mmHg mean-gradient cutoff.
Also, by the simplified Bernoulli equation:
[
\Delta P_{\text{peak instantaneous}} = 4V^2 = 4(4)^2 = 64\ \text{mmHg}
]
So Vmax 4 m/s corresponds to a peak instantaneous Doppler gradient of about 64 mmHg, which supports severe obstruction. Overall: severe, high-gradient AS if the reported 40 mmHg is the mean Doppler gradient.
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