Mechanisms of occurrence
A pathological sound phenomenon during the ventricular relaxation phase develops in two classic hemodynamic scenarios:
- Atrioventricular valve stenosis. Blood is forced to push through a narrowed orifice into the ventricle (an example is mitral stenosis). The flow is especially intensified at the moment of atrial systole.
- Semilunar valve regurgitation. The cusps do not close completely, and part of the blood flows back (regurgitates) from the aorta or pulmonary trunk back into the ventricles.
Classification by diastole phases
Diastole lasts for a certain time, and the murmur can occupy different intervals of it:
- Early (protodiastolic). They appear immediately after the II sound and fade before the I sound. Typical for backflow through defective semilunar valves (aortic regurgitation).
- Middle (mesodiastolic). Recorded with a short pause after the II sound. Characteristic of turbulent flow through AV orifices. They may fade away or flow into the late phase.
- Late (presystolic). Start in the middle of diastole and sound until the I sound itself. Their intensity increases due to atrial systole (increased flow velocity).
Auscultation pattern of main defects
| Characteristic | Mitral stenosis | Aortic regurgitation |
|---|---|---|
| Localization (punctum maximum) | Apex of the heart | 2nd right intercostal space |
| Irradiation | Absent | Botkin-Erb point |
| Timbre | Rumbling | Blowing |
| Frequency | Low | High |
| How to auscultate | With the stethoscope bell, in the left lateral position, on expiration | With the diaphragm, sitting leaning forward, on expiration |
| Associated findings | Opening snap of the mitral valve, loud I sound | High pulse pressure, systolic ejection click |
Specific diastolic murmurs
In addition to typical patterns, specific phenomena occur:
- Graham Steell murmur. This is a protodiastolic murmur heard in the second left intercostal space. It indicates pulmonary valve regurgitation that has developed against the background of severe pulmonary hypertension (the fibrous ring has stretched).
- Austin Flint murmur. A functional murmur mimicking mitral stenosis (sounds at the apex, has a mesodiastolic or presystolic character). It develops in severe aortic regurgitation: the regurgitation jet strikes the anterior mitral cusp, pushing it away and creating a relative stenosis of the AV orifice. The cusps themselves are not structurally altered.
Briefly: answers to topical questions
In which other heart defects, besides mitral stenosis, can a mesodiastolic murmur occur?
In addition to organic mitral stenosis, a mesodiastolic murmur can be heard in aortic and mitral regurgitation, as well as in prosthetic valve dysfunction.
- Severe mitral regurgitation — a functional, short mesodiastolic murmur (Coombs murmur) occurs due to the relative stenosis of the left atrioventricular orifice.
- Severe aortic regurgitation — a functional mesodiastolic or presystolic murmur (Austin Flint murmur) is formed, associated with the relative narrowing of the lumen due to the impact of regurgitant blood on the mitral valve cusp.
- Mitral valve prosthesis thrombosis — appearance of an early mesodiastolic murmur.
- Bioprosthesis dysfunction — an early mesodiastolic murmur occurs when cusps fuse and prosthesis stenosis forms.
Class and exam questions
Can a diastolic murmur be functional in a healthy person?
No, the appearance of a murmur during the diastole phase is always a sign of an organic lesion (pathology). Only systolic murmurs can be functional.
Why does the murmur intensify before the I sound in mitral stenosis?
This presystolic intensification is associated with atrial systole. At the end of diastole, the atrium contracts, increasing the velocity and turbulence of the blood flow through the narrowed orifice.
How to properly auscultate a faint murmur of aortic regurgitation?
A diaphragm stethoscope should be used (the murmur is high-frequency). The patient should sit leaning forward and hold their breath on expiration.
What is the essence of the Austin Flint phenomenon?
This is the formation of relative mitral stenosis without organic damage to the valve itself. The blood stream from the aorta pushes the mitral valve cusp aside, hindering the normal blood flow from the atrium.
What else to study on this topic
- Hemodynamics in mitral stenosis
- Hemodynamics in aortic regurgitation
- Differential diagnosis of organic and relative mitral stenosis
- Causes and consequences of pulmonary hypertension (in the context of the Graham Steell murmur)
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