17887129053295496700239593032350.jpg
Explain the 5th point
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isovolumetric contraction rate of pressure rise dP/dt first heart sound intensity
5. Rate of pressure rise during isovolumetric contraction: dP/dt
Isovolumetric contraction is the very early part of ventricular systole, just after the mitral and tricuspid valves close. For a brief moment, all valves are closed, so ventricular volume does not change, but ventricular pressure rises rapidly.
dP/dt means the rate at which ventricular pressure rises:
- Higher dP/dt = ventricle contracts more rapidly and forcefully.
- Lower dP/dt = pressure rises slowly because contraction is weak or the ventricle is not a properly closed chamber.
This matters because S1 is produced mainly by sudden closure and tensing of the AV valves. A rapid pressure rise produces a more abrupt valve closure and hence a louder S1. The mitral component of S1 occurs with the abrupt rise in LV pressure during isovolumetric contraction, and increased ventricular pressure development is associated with a louder S1, as described in Clinical Methods.
a. Leaky AV valve, such as mitral regurgitation
In mitral regurgitation (MR), the mitral valve does not close tightly. Some LV blood leaks backward into the left atrium during systole.
So:
Leaky mitral valve → ineffective/shortened isovolumetric contraction → less effective rise in LV pressure (↓ dP/dt) → less abrupt valve closure → soft S1.
In myocarditis, impaired myocardial contractility can also reduce dP/dt and make S1 softer.
b. Exercise or high-output states
During exercise, sympathetic stimulation increases myocardial contractility.
So:
Exercise/high-output state → ↑ contractility → rapid LV pressure rise (↑ dP/dt) → more forceful, abrupt AV-valve closure → loud S1.
The same principle explains why hyperadrenergic states, such as anxiety, fever, anemia, thyrotoxicosis, and pregnancy, can produce a loud S1.
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Doesn't this contradicts the 4th point
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S1 intensity mitral stenosis delayed closure mitral regurgitation isovolumetric contraction Clinical Methods
No. Points 4 and 5 are describing two separate determinants of S1 intensity:
- Timing/position of the AV valve at the start of systole
- Speed of LV pressure rise and effectiveness of valve closure
They can both act at the same time.
| Condition | Valve position/timing | Pressure rise or closure | Effect on S1 |
|---|---|---|---|
| Mitral stenosis | High LA pressure keeps mitral leaflets widely open until systole, so closure is delayed | Leaflets have a large excursion and are still mobile | Loud S1 |
| Mitral regurgitation | Valve is incompetent, so it cannot form a tight seal | Blood escapes into LA during systole, the true isovolumetric phase is lost or reduced, and closure vibrations are less effective | Soft S1 |
| Acute aortic regurgitation | Rising LV diastolic pressure may partly close the mitral valve before systole | There is little further excursion at systole | Soft S1 |
| Exercise/high-output state | Timing may be normal | Increased contractility causes rapid LV pressure rise, high dP/dt | Loud S1 |
The apparent contradiction
In mitral stenosis, the delay is due to high left atrial pressure. LV pressure needs longer to exceed LA pressure, so the mitral valve closes later. But the valve is held wide open before it closes. Therefore, its leaflets travel a greater distance and shut more forcefully, producing a loud S1.
In mitral regurgitation, even if there is no early closure, the issue is different: the valve is leaky, so the ventricle is not a fully closed chamber during early systole. Blood immediately regurgitates into the atrium. This reduces the normal sharp, effective closure vibration and may eliminate the true isovolumetric contraction period. Thus S1 is soft.
So remember:
Delayed closure with mobile, widely separated leaflets = loud S1
Ineffective closure due to a leaking valve = soft S1
One correction to the handwritten fifth point: saying MR simply causes “loss of dP/dt” is an oversimplification. More accurately, MR causes loss/shortening of effective isovolumetric contraction and may blunt the pressure rise relevant to valve closure; the accompanying systolic murmur can also mask S1. Clinical Methods describes these mechanisms.
Can we say that the dp/dt is less in premature closure of valve and dp/dt is more in delayed closure of valve?
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first heart sound premature delayed mitral valve closure dP/dt
No. Do not equate timing of valve closure with dP/dt. They are related through pressure differences, but one does not reliably predict the other.
Mitral valve closure occurs when:
LV pressure becomes greater than LA pressure.
So the time of closure depends on both:
- how fast LV pressure rises, meaning dP/dt
- the starting LA pressure and valve position
Key distinction
| Situation | Main reason | dP/dt |
|---|---|---|
| Premature mitral closure | LV diastolic pressure becomes high early, such as acute severe AR | May be normal, not necessarily low |
| Delayed closure in mitral stenosis | LA pressure is high, so LV takes longer to exceed it | May be normal, not necessarily high |
| Delayed closure due to weak LV contraction | LV pressure rises slowly | Low dP/dt |
Thus, delayed closure can actually occur with low dP/dt if weak ventricular contraction makes LV pressure rise slowly. In mitral stenosis, however, the usual reason for delayed closure is elevated LA pressure, not increased dP/dt.
Similarly, premature closure does not mean low dP/dt. In acute AR, rapid LV filling raises LV diastolic pressure and can shut the mitral valve before systole, producing soft S1. Harrison’s describes this as premature mitral closure from elevated LV diastolic pressure, while standard physiology defines S1 closure as occurring when LV pressure exceeds LA pressure.
A safer exam statement is:
Valve closure timing depends on when LVP crosses LAP.
S1 intensity also depends independently on leaflet excursion/mobile valve anatomy and the rapidity of pressure development, dP/dt.
So:
- Delayed closure in MS → usually loud S1 because leaflets are wide apart and mobile.
- Low dP/dt → usually soft S1 because closure is less abrupt.
- These are separate mechanisms, not opposites.
dp/dt depends on contraction of ventricle?
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LV dP/dt ventricular contractility preload afterload physiology
Yes. LV dP/dt mainly reflects the rate and strength of ventricular contraction, particularly during isovolumetric contraction.
[
dP/dt = \frac{\text{change in ventricular pressure}}{\text{change in time}}
]
- Increased contractility: LV muscle develops tension faster → LV pressure rises faster → ↑ dP/dt
- Reduced contractility: LV develops tension slowly → LV pressure rises slowly → ↓ dP/dt
Examples:
- Exercise, sympathetic stimulation, catecholamines → ↑ contractility → ↑ dP/dt → usually louder S1.
- Myocarditis, myocardial infarction, cardiomyopathy, heart failure → ↓ contractility → ↓ dP/dt → softer S1.
But it is not a perfectly pure measure of contraction because preload can influence it too. Still, clinically and physiologically, a higher peak LV dP/dt is used as an index of better contractility. Morgan and Mikhail states that systolic ventricular dP/dt is directly proportional to contractility, while Katzung notes that reduced contractility lowers the rate of intraventricular pressure development.
How does dp/dt affect S1 intensity
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site:ncbi.nlm.nih.gov/books first heart sound increased rate pressure development intensity S1
S1 is the vibration produced when the mitral and tricuspid valves close and their leaflets, chordae, and surrounding blood column suddenly tense.
dP/dt determines how abruptly that closure occurs.
If dP/dt is high
The ventricle generates pressure very rapidly.
[
\text{Rapid LV pressure rise} \rightarrow \text{rapidly exceeds LA pressure} \rightarrow
\text{brisk mitral-valve closure} \rightarrow \text{larger vibrations} \rightarrow \mathbf{loud\ S1}
]
Example: exercise or sympathetic stimulation increases contractility, causing a rapid pressure rise and a loud S1.
If dP/dt is low
The ventricle develops pressure slowly.
[
\text{Slow LV pressure rise} \rightarrow \text{slow, less abrupt valve closure} \rightarrow
\text{smaller vibrations} \rightarrow \mathbf{soft\ S1}
]
Example: myocardial infarction, myocarditis, cardiomyopathy, or cardiogenic shock can reduce contractility and dP/dt, giving a soft S1.
The important wording
dP/dt affects the velocity/forcefulness of valve closure, not necessarily whether closure is early or late.
- Timing of closure: when LV pressure crosses LA pressure. It also depends on LA pressure and the valve's starting position.
- Intensity of S1: how far apart/mobile the leaflets are, and how abruptly LV pressure rises, meaning dP/dt.
Clinical Methods specifically identifies increased ventricular pressure-development rate as the main reason hypercontractile states produce a loud S1, and reduced pressure development as a cause of soft S1 in myocardial depression.
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