Cardiac Sounds

Heart Sounds

Heart Sounds are noise which is produced by the varied activities like the beating of the heart and also flows of blood through heart results production of the heart sound. the most cardiac event like tensing of Chordae Tendineae or valve closure also causes the sound of heart produced. Auscultation of the centre heart sound is that the act of listening to the unique and distinct sound of heart by using a stethoscope on the chest over the different region of the heart. You will get a good knowledge of a normal heart sound. Similarly, you will be able to differentiate the abnormal heart sounds.

Mainly heart sound is short audible and in discrete event form. There are both normal and abnormal heart sound Where first heart sound (S1) and Second Heart Sound (S2) are totally normal whereas third heart sound(S3) and fourth heart sound (S4) are pathogenic also among S3 and S4, third heart sound (S3) is somewhat normal and sometimes it is often pathological too. This was the concern of heart sounds s1 s2 s3 and s4. The sounds are also concerned with the heart sounds location which is explained below.

Heart sound is described on the idea of the pitch which may be highly pitched, Intensity both loud, soft and offset. Loud is because of increase in intensity and soft is because of decrease in intensity Heart sounds are often also determined by the placement from where it’s produced which also helps in the determination of the aetiology of assorted diseases. Heart sound timing can even be described as early-mid or late systole or diastole. There are mainly two sorts of heart sounds. i.e.

Normal Heart Sound – the primary heart sound (S1) and second heart sound (S2) are the conventional heart sound. Mainly it’s also explained as a LUB and a dub which often occurs in sequence with each heartbeat and both S1 and S2 are produced by the closure of valves. i.e both heart sounds are produced by the closing of the atrioventricular valve and Cardiac semilunar valve respectively.

Abnormal Heart Sound – it’s possible to be called as a cardiac murmur. A murmur means the sound produced by rough blood supply through the centre of heart valves or near the valves. The rasping, whooshing and blowing is murmur. there are two main forms of murmur they’re. : innocent murmur which is additionally called as physiological which may be found in both children or in adults. it’s mainly caused by physical activities and through fever or pregnancy.

Abnormal murmur is found in a child. it’s because of the congenital heart malfunction and abnormal murmur found in an adult is because of the valves separating the heart’s chamber.

First heart sound (S1)

First heart sound is produced because of the closure of the mitral valve and tricuspid valve first heart sound is produced and represented or termed as S1. The component of S1 are M1 and T1. Where M1 is termed as the sound produced by closure of mitral valve and T1 is termed as the sound produced by closure of the tricuspid valve. M1 Sound has high within the left side of the heart so it’s much louder than T1 sound. Thus, all cardiac listening post is radiated by M1. the primary heart sound coincides with the carotid pulse. hear the primary sound

heart sound and judge if it appears loud, quiet or split. the primary heart sound isn’t usually audibly split, despite the actual fact that it represents the closure of the mitral and tricuspid valves and these two events aren’t completely synchronous.

It forms the “LUB” of “LUB-DUB”

Heart sounds
Position: Mitral          Chest piece: Diaphragm

The S1 sound produced from the reverberation within the blood related to the sudden block of flow reversal by both semilunar and atrioventricular valves. delay in T1 sound over normally causes the split of S1 which might be heard in a very right bundle branch block. T1 is best heard over the fourth ICS at the left sternal border of heart, and M1 is best heard near the apex of the heart.

The position of valves at the tip of ventricular diastole determines the intensity of S1. The farther apart the leaflets are at the start of systole, the rapid closure of semilunar and atrioventricular valve and also the louder is S1. within the same way, the leaflets of valves are closer to every other at the start of the systole, shorter the gap of travel required for valvular apposition and also the softer the S1.

The leaflets are far apart with an increased transvalvular gradient (ie, MS or tricuspid stenosis [TS]), transvalvular flow increases, tachycardia, and preexcitation syndromes. When leaflets of AV valves don’t seem to be able to oppose properly, ends up in a muffled S1. acute aortic regurgitation (AR), left ventricular (LV) end-diastolic pressure rapidly rises; thus, the faster equilibration of ventricular and atrial pressures, finally ends up in early closure of mitral valve and a muffled S1 occurs.

Muffled S1 occurs when there’s an increase in the amount of tissue within the heart, in pericardial effusion, emphysema, pneumothorax, and obesity.

Split in S1

Normally, when the mitral valve closes just before the tricuspid valve. Thus, M1 is audible before T1 was a difference that’s often not detectable

Splitting of S1 is more detectable when there’s the time difference between the closure of the mitral and also the tricuspid valves get increased.

This mainly happens because of early closure of the mitral valve or by the late closure of the tricuspid valve with reference to the mitral valve.

Heart sounds
Position: Tricuspid           Chest piece: Diaphragm

Some of the conditions related to a split S1 include the following:

Premature ventricular contractions (PVCs) of LV origin: it’s the most typical case of the irregular rhythm of the heart. it’s an event where the heartbeat is initiated by Purkinje fibre.

Right bundle branch block: the heart block within the right bundle branch of the conduction system is supposed to be right bundle branch block (RBBB). Right heart ventricle isn’t directly initiated by impulses travelling by the proper bundle branch.

LV pacing: it avoids the deleterious effect of the right atrium of the heart pacing.

Reverse splitting of S1 occurs when the sound produced by the mitral valve follows the closure sound of the tricuspid valve. Delayed Closure of mitral valve also come up with a condition like left bundle branch block, right ventricular (RV) pacing, severe MS, and left atrial myxoma.

Second heart sound(S2) :

Second heart sound is produced due to the closure of the aortic valve and pulmonary valve second heart sound is produced and represented or termed as S2. The component of S1 are A2 and P2. Where A2 is termed as the sound produced by closure of Aortic valve and P2 is termed as the sound produced by closure of the pulmonary valve. At aortic area i.e second right intercostal space, A2 is best heard.

Heart sounds
Position: Pulmonic             Chest piece: Bell

And at near the diaphragm P2 is best heard by the assistance of stethoscope. The sound produced by Arotic valve(A2) is generally much louder than the sound produced by closure of pulmonary valve (P2) because of high pressures within the left side of the heart; hence, A2 spreads to all or any cardiac listening posts and it is loudest at the right upper sternal border and P2 is typically only heard at the left upper sternal border. Therefore, the A2 sound is the main component of S2.

Split S2

The aortic valve closing slightly before the pulmonary valve causes S2 splitting. and it is more prominent while taking breathe. The opening of pulmonary and therefore the aortic valves remain short after the end of systole and after the left ventricle and right ventricle pressures becomes lowered compared to aortic pressures. The interval between this particular valve closure and pressure crossover between ventricles and great vessels provides inverse proportion to the resistance of blood flow through great vessels. and these blood flow, resistance accounts for delayed closure of pulmonary valve relative to the aortic valve.

There are various S2 splitting they are

1.Physiologic Split S2: The combination of A2 and P2 makes up S2, where A2 Comes just before P2.

It occurs when A2 sound comes before P2 by a greater distance to permit both sounds to be heard separately. During inspiration, venous return increases which delay the closure of pulmonary valve which is major effects and decrease in venous return to the left side of the heart hasten the closure of the aortic valve which is a minor effect. When the gap gets narrower during expiration Split S2 isn’t any longer audible.

2.Paradoxical Split S2

when the splitting is heard during exhalation and disappears during inhaling then, paradoxical split S2 heart sound occurs it’s opposite of the physiologic split S2. It occurs altogether setting that delays the closure of the aortic valve including severe stenosis and hypertrophic obstructive cardiomyopathy, or within the presence of a left bundle branch block.

3.Persistent (Widened) Split S2

when both A2 and P2 are audible during the entire respiratory cycle, Persistent (Widened) Split S2 occurs. Splitting becomes high prominent inspirationally and less prominent with expiration. Any condition which causes an uncertain delay within the pulmonic valve closure, or aortic valve get closed earlier, will cause a wide split S2. Hence, a persistent split S2 would occur within the RBBB setting, pulmonary hypertension or pulmonic stenosis ( or severe mitral regurgitation/ventricular congenital heart defect (early A2 closure). Causes wide persistent splitting of S2

4.Fixed Split S2: sound is produced by the closure of the aortic and pulmonic valves cause the production of S2 sound. when there’s always a delay within the closure of the pulmonic valve and there’s no further delay with inspiration then fixed split S2 occurs. it’s Split during is also called as Reverse splitting which indicates pathology. If splitting doesn’t vary with inspiration, it’s termed a “fixed split S2” and it is especially caused because of a congenital heart defect, like an atrial septal defect (ASD).

Third Heart Sound(S3)

The early diastolic sound which is audible when there is the rapid entry of blood from the article to the ventricle is third Heart Sound. It is a low pitched sound. When it arises from the left ventricles, At the apex of the heart in the patient with left lateral decubitus position when breath held at the end of expiration.

When it arises from the right ventricles, at the left lower sternal border or the xiphoid with the patient in supine position S3 is heard best. While blood rapidly rushes from auricle is suddenly decelerated by the ventricle then S3 occurs. In a normal heart ventricle, S3 occurs when the excess volume of blood comes to heart, also can happen in hyperdynamic states or volume loaded conditions.

Heart sounds
Position: Mitral             Chest piece: Bell

S3 is physiologically found in the patient below the age of 40 years old. Those patient have got mainly thin chest wall which permits easy transmission of S3.

The pathological conditions related yo the S3 are as follows:

  1. Dysfunction of ventricular systolic is clinical Syndrome related to left ventricle failure while diastolic syndrome is related to pulmonary congestion together with a normal or only slightly enlarged ventricle.
  2. Ischemic heart disease is the Coronary Heart Disease (CHD) relates with the heart which is not getting enough blood and oxygen.
  3. Acute s aortic regurgitation (AR): It is related to the rapid disruption of the anatomic integrity of the aortic valve.

Fourth Heart Sound:

The late diastolic sound which corresponds to the late ventricular filling through an active atrial contraction is fourth Heart sound(S4). The fourth heart sound is low-intensity sound. When sound originates from the left ventricle, S4 best heard at the apex of heart within the patient with left lateral decubitus position when breath held at the end of expiration. When it arises from the proper ventricles, at the left lower sternal border. The intensity of S4 increases when the separation of S4 from S1.

S4 isn’t audible with the arterial defibrillation as ventricular theory proposes deceleration of the jet of blood because it enters a ventricle and therefore the impact theory proposes the movement and impact of the ventricle on the chest wall because the jet of blood from atrial systole strikes the ventricle.

Some of the conditions related to S4 include the following:

  1. Ventricular aneurysms: It refers to the bluge or the pocketing within the heart lining of a vessel at the bottom of the septum or within the aorta.
  2. Hyperkinetic states that cause forceful atrial contraction causes fever, cancer etc.
  3. Ischemic heart condition is that the Coronary heart condition (CHD) relates with the heart which isn’t getting enough blood and oxygen.

S3 and S4 is differentiated from splitting of the conventional heart sounds. With splitting, the heart sounds are high pitched and best audible with the diaphragm, whereas the S3 or S4 are low-pitched sounds best audible with the bell of the stethoscope.


To conclude, the s1 and s2 heart sounds are normal. The s3 and s4 heart sounds (especially s4) are pathogenic. The s3 heart sound is treated somewhat normal but maybe pathogenic as well. While the s4 heart sound is surely pathogenic.

We hope that you may have known what is sounding in terms of heart. Now that you hear a heart sound audio, you will experimentally get the knowledge of the heart sounds we mentioned.

Frequently Asked Questions

1. where to listen to heart sounds?

Heart sound can be listened best by the stethoscope by the auscultation Where stethoscope consists of bell and diaphragm. Bell is used for listening to low-pitched sounds. Example: the mid-diastolic murmur of mitral stenosis or S3 in the heart.

The diaphragm is used for listening filtered high pitched sound Example: the early diastolic murmur of aortic regurgitation. Example: the early diastolic murmur of aortic regurgitation.

2. Normal heart sounds are caused by which of the following events?

Normal heart sounds are caused by the contraction of different auricle and ventricles, the flow of blood from hearts to different parts of the body and vice versa, closure of various heart valves, and also produced by the beating of hearts while doing exercise, playing games, during fever etc

3. where to auscultate heart sounds

The heart sound is best heard at the apex of heart, at the base part of the heart between the apex and the sternum and in the aortic and pulmonic area heard best as left and right sternum respectively


Dr Aadarsh Yadav

Dr Adarsh Yadav is a registered medical expert currently is a medical officer at the department of paediatrics at Scheer memorial Adventist hospital, kavre, Nepal. He had been a very well trained medical practitioner, and apart from his medical practice, he had been a member of different health camps organizing blood donation camps in Bangladesh just during his internship.

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