What Causes The Heart Sounds?

What Are Heart Sounds?

According to this use of the terminology, heart sounds are the sounds emitted by the closure of the heart valves and the flow of the blood in the heart chambers. First, the normal sounds S1 and S2 are the opening of the atrioventricular valves: tricuspid and mitral, and semilunar valves – pulmonary and aortic, respectively. They are useful for evaluating conditions concerning the heart’s performance and beat. Extra-systolic sounds, such as S3 and S4 or murmurs, suggest disease states like congestive heart failure, valvular diseases, and/or congenital anomalies. There is therefore need to distinguish and understand these sounds if any intervention or management of Cardiovascular diseases is to be done.

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Primary Heart Sounds (S1 and S2)

The primary heart sounds are listed below:

First Heart Sound (S1)

• Cause:

S1 also known as the first heart sound is the sound produced by the closure of the fourth atrioventricular valve; the mitral and tricuspid.

• Timing:

This is at S1 that ventricular systole initiates and it is a phase whereby the ventricles contract to eject blood.

• Characteristics:

This sound is well known as the ‘lub’ sound and is louder and lasts longer than the second sound.

Second Heart Sound (S2)

• Cause:

The second heart sound (S2) that is produced by the closure of semilunar valves includes aortic and pulmonary valves.

• Timing:

S2 is widely viewed as concluding ventricular systole while the process of diastole is thought of as the process through which the ventricles remain open and eject their blood.

• Characteristics:

This sound is known as ‘dub’; it is slightly different from S1 in the way that it is shorter than S1 and also has a sharper sound.

Additional Heart Sounds (S3 and S4)

The additional heart sounds are listed below:

Third Heart Sound (S3)

• Cause:

S3 is produced by early diastolic filling of the ventricles as a result of blood being remarked into the relatively non-contracted ventricles by the atria.

• Timing:

S3 is conducted after S2, this is perhaps in the first phase of the diastolic phase of the cardiac cycle.

• Characteristics:

It is a loud, low-pitched sound sometimes referred to as a ventricular gallop and is worse with the diaphragm of the stethoscope.

• Clinical significance:

S3 can be physiological in young individuals and physically fit individuals because of increased cardiac output, but in the elderly, it may be a sign of heart failure/volume overload.

Fourth Heart Sound (S4)

• Cause:

S4 is produced by atrial systole against the closed and stiff or thick ventricles, resulting in increased blood turbulence.

• Timing:

S4 happens immediately before S1, specifically in the beginning of diastroke as the atria eject blood onto the ventricles.

• Characteristics:

It is a low-pitched, low-frequency murmur that is described as having an ‘atrial gallop;’ he heard best using the bell of the stethoscope.

• Clinical significance:

S4 is normally seen in conditions that diminish the ventricles’ compliance, for example, hypertensive heart disease or left ventricular hypertrophy.

Abnormal Heart Sounds: Murmurs

The abnormal heart sounds are listed below:

Heart Murmurs

• Causes:

Heart murmurs are noises associated with blood flow through and/or around the heart and its valves or from structural abnormalities in the heart, including stenosis and incompetence. These irregularities cause a turbulent circulation of blood and this as we all know is measured as a murmur.

• Types:

Systolic Murmurs: They happen between S1 and S2 when ventricles are contracting. There are usual types such as those due to aortic stenosis or mitral regurgitation.

Diastolic Murmurs: Occur during ventricular diastole between S2 and S1 extremely close to each other. Examples of benign heart sounds include those produced by aortic stenosis or murmurs from it or murmurs from mitral stenosis.

Continuous Murmurs: Last the duration of the cardiac cycle such as those due to ductus arteriosus.

• Clinical significance:

Heart murmurs are very vital in diagnosing heart diseases as well as judging the severity of the diseases. These may signify structural abnormalities of the heart and assist in the subsequent investigations and management plans.

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