Technique and instruments
High-quality auscultation requires silence and proper instrument use. If the patient has excessive body hair, it is recommended to moisten the skin with soapy water or water to avoid crackling sounds that mimic rales or murmurs.
- Stethoscope (diaphragm): Used to assess high-pitched sounds. These include the first and second heart sounds, pericardial friction rub, and murmurs associated with aortic or mitral regurgitation. Rule: the diaphragm must be pressed firmly against the chest wall.
- Stethoscope (bell): Used for low-pitched sounds (third and fourth heart sounds, mitral stenosis murmur). Rule: the bell is applied lightly. Hard pressure stretches the skin, causing it to act like a diaphragm and filter out the required low frequencies.
The basic patient position is supine. To detect subtle acoustic signs, additional positions are used: left lateral decubitus (improves mitral valve auscultation), prone, sitting, standing, as well as after physical exertion or during breath-holding.
Topography of the main auscultation points
Auscultation is performed in a strict sequence tied to bony landmarks. The localization of the sound depends on the direction of blood flow rather than the anatomical projection of the valve.
- Mitral valve (1st point): Apex of the heart — 5th intercostal space on the left, 1–1.5 cm medial to the left midclavicular line (linea medioclavicularis sinistra).
- Aortic valve (2nd point): 2nd intercostal space on the right, right at the sternal border.
- Pulmonary valve (3rd point): 2nd intercostal space on the left at the sternal border.
- Tricuspid valve (4th point): Lower part of the sternal body, at the base of the xiphoid process.
- Erb's point (5th point): 3rd intercostal space on the left at the sternal border. This is an additional area for evaluating the aortic valve (the diastolic murmur of aortic regurgitation is heard most distinctly here).
Normal heart sounds: S1 and S2
In a healthy individual, two main heart sounds are heard. The mechanism of their generation is associated with the vibrations of the valve apparatus and myocardial contraction.
First heart sound / S1 (systolic): Occurs at the beginning of ventricular systole (during the period of isometric contraction). It coincides with the closure of the atrioventricular valves and myocardial contraction. It has four components:
- Valvular (main): tension of the elastic tissue of the closed cusps.
- Muscular: vibrations of the ventricular myocardium during contraction.
- Vascular: vibrations of the aortic and pulmonary trunk walls.
- Atrial: atrial contraction.
S1 is heard best at the apex of the heart (where the mitral component predominates).
Second heart sound / S2 (diastolic): Occurs at the beginning of diastole due to the snapping shut of the semilunar valves (aortic and pulmonary). It is louder at the base of the heart (in the 2nd intercostal space).
The sounds can be distinguished by their pauses: between S1 and S2 is the short systolic pause, and between S2 and the subsequent S1 is the long diastolic pause.
Changes in S1 intensity
Pathological changes in S1 intensity (accentuation or muffling) are evaluated exclusively at the apex of the heart.
Muffling of S1:
- Valvular factor: Mitral or tricuspid regurgitation. The cusps do not close tightly, the period of closed valves is absent, and the valvular component is thereby reduced.
- Muscular factor: Severe heart failure (decreased myocardial contractility diminishes the muscular component).
Accentuation of S1:
- Valvular causes: In mitral stenosis, S1 becomes "booming" or "slapping". Due to shortened diastole, ventricular filling is impaired, and a sharp myocardial tension occurs by the onset of systole.
- Hemodynamic causes: Increased cardiac output (exercise-induced tachycardia, thyrotoxicosis, anemia). The rate of blood ejection and the force of contraction increase.
Briefly: answers to topical questions
In which pathologies does splitting or duplication of the second heart sound occur?
Splitting or duplication of the second heart sound occurs in valvular aortic stenosis. In this case, paradoxical splitting is observed, where the aortic component of the sound lags behind the pulmonic component (closure of the pulmonary valve). This pathological sign is usually more pronounced during expiration. Normally, the second heart sound at the base of the heart also consists of aortic and pulmonary components, but splitting is diagnosed when they are heard separately.
What is the mechanism of formation of the third and fourth additional heart sounds?
The third and fourth additional heart sounds are associated with alterations in myocardial properties: decreased contractility, left ventricular dilation, and heart failure.
- Third heart sound (S3) — an extra sound in early diastole, following S2; it causes a protodiastolic gallop rhythm. In severe decompensation with systolic dysfunction, a protodiastolic gallop rhythm with S3 may be auscultated.
- Fourth heart sound (S4) — an extra sound preceding S1; it causes a presystolic gallop rhythm. In aortic stenosis, the pathological S4 in the compensated stage is associated with enhanced left atrial contraction and left ventricular stiffness.
How do organic heart murmurs differ from functional ones?
Organic heart murmurs are associated with structural changes that disrupt laminar blood flow: stenosis, valve regurgitation, or abnormal shunt communications. Pathological ejection murmurs occur in organic valve disease.
| Characteristic | Organic murmurs | Functional murmurs |
|---|---|---|
| Cause | Structural changes: stenosis, valve regurgitation, shunt communications. | Relative stenosis without organic narrowing of the corresponding orifice; diastolic functional murmurs have also been described in patients with renal failure in the setting of anemia. |
| Examples | Pathological ejection murmurs in valvular heart disease. | Austin Flint murmur, Coombs murmur; diastolic functional murmur in renal failure in the setting of anemia. |
What are the causes of a systolic murmur at the apex of the heart?
A systolic murmur at the apex of the heart occurs as a result of pathologies that disrupt normal hemodynamics in the area of the mitral valve during systole.
- Mitral regurgitation — causes a blowing pansystolic murmur due to the backflow of blood (regurgitation).
- Mitral valve prolapse — accompanied by a systolic murmur due to the development of regurgitation against the background of leaflet billowing.
- Mitral stenosis — according to modern clinical data, a systolic murmur is also possible in isolated, pure stenosis of the left atrioventricular orifice.
To avoid confusion during accelerated heart rates (tachycardia) when the pauses between sounds even out: S1 always coincides with the apical impulse or palpable carotid artery pulsation.
Class and exam questions
Why do auscultation points not coincide with the anatomical projection of the valves?
Because the acoustic phenomena generated by valve function are best conducted along the direction of blood flow. It is precisely in these remote zones that audibility is maximal.
At which point should pathology of the second heart sound be assessed?
Changes in the second heart sound (its accentuation, diminution, or splitting) are assessed exclusively at the base of the heart, i.e., in the second intercostal space to the right and left of the sternum.
How to differentiate splitting of the second heart sound from an extra sound at the apex?
An additional sound immediately following the second heart sound at the cardiac apex is not splitting, but an extra sound (for example, the opening snap of the mitral valve). True splitting of the second heart sound is assessed at the base of the heart.
Why are heart sounds quiet in obese patients?
This is due to extracardiac factors. An increased thickness of the chest wall impairs sound conduction from the heart to the body surface. The same effect is caused by fluid accumulation and pulmonary emphysema.
What else to study on this topic
- Component composition of the first heart sound in health and disease
- Mechanism of formation and causes of splitting of the second heart sound
- Additional sounds: opening snap of the mitral valve
- Impact of extracardiac factors on the auscultatory picture
- Specifics of auscultating murmurs in additional postures (in the lateral decubitus position, standing)
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