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heart sounds

With an ear applied to the chest — or more usually, with a stethoscope — it is normally possible to detect two sounds in every heart beat, which are produced when the valves of the heart close. The sounds arise from the brief turbulence of blood flow occurring just as a valve closes. The left side of the heart develops a higher pressure than the right side, which means that the sounds produced there, by the mitral (bicuspid) valve between atrium and ventricle, and the aortic valve at the exit from the ventricle, are generally louder and precede the sounds produced from the equivalent valves on the right side (tricuspid and pulmonary valves). The first heart sound is produced by closure of the two atrio-ventricular valves, when the ventricles start to contract. It is often described as ‘lub’; the ‘l’ reflecting the louder mitral valve closure preceding the quieter tricuspid valve closure ‘b’. Deep inspiration widens the split between mitral and tricuspid closure: ‘lu-ub’. The second heart sound is produced by closure of the aortic and pulmonary valves (between the ventricles and their respective arteries), and is often described as ‘dup’; the ‘d’ reflecting the louder aortic valve closure preceding the quieter tricuspid valve closure ‘p’. With experience, the two sounds can be distinguished by pitch and intensity; also at a resting heart rate there is a longer interval between beats than between the two sounds.

heart murmurs are soft sounds, like those made during a forcible expiration with the mouth open. They are most often caused by any departure from the crisp sounds described here which reflect equally crisp function of the valves. Valves may become leaky, allowing backflow (incompetence), or they may become stiff and narrow (stenosis). Stenosis, for example, of the aortic valve leads to an abnormal turbulence during ejection of blood through it from the left ventricle, so it is a systolic murmur because it occurs during the phase of contraction (systole), preceding the second heart sound at the closure of the valve. Incompetence of this same valve allows some blood to flow back into the ventricle causing a diastolic murmur at the time of the second sound when it closes incompletely during ventricular relaxation (diastole). An incompetent mitral valve allows blood to regurgitate into the left atrium throughout ventricular contraction, causing a systolic murmur, whereas mitral stenosis causes a murmur as the blood flows from atrium to ventricle during diastole.

Other characteristic murmurs are caused by congenital defects, such as a hole in the ventricular septum, or a failure of closure of the connection between aorta and pulmonary artery which is present before birth (patent ductus arteriosus).

A murmur is classified with respect to its intensity (just audible, soft, moderate, or loud), the point on the chest wall where the murmur is heard best (which assists its localization to a particular valve or part of the heart), and the timing of the murmur in the heart beat (in relation to the first and second heart sounds).

Not all murmurs signify abnormality of the heart. Systolic murmurs, due to normal turbulence during ventricular contraction and ejection of blood, may be present particularly in young people, and not uncommonly in exercise and in pregnancy.

— David J. Miller, Niall G. MacFarlane

See also heart; sounds of the body.

 
 
Dental Dictionary: heart sounds

n.pl

Normal noises produced within the heart during the cardiac cycle that can be heard over the precordium and may reveal abnormalities in cardiac structure or function. The use of the stethoscope over the left side of the chest is a common clinical technique to assess heart function. The typical sounds are a rythmic lub dup; abnormal sounds include clicks, murmurs, rubs, snaps, and gallops.

 

Normally, during one cardiac cycle, two heart sounds (usually described as ‘lub-dub’ or ‘lub-dup') that can he heard over the chest through a stethoscope. The first sound is caused by closure of the atrioventricular valves towards the beginning of systole, the other is caused by the closure of the semilunar valves guarding the aorta and pulmonary artery at the beginning of ventricular diastole. Compare heart murmur.

 
Veterinary Dictionary: heart sounds

The sounds heard on the surface of the chest in the heart region. They are amplified by and heard more distinctly through a stethoscope. These sounds are caused by the vibrations of the normal cardiac cycle. They may be produced by muscular action, valvular actions, motion of the heart, and blood as it passes through the heart.
The first heart sound (S1) is heard as a firm but not sharp ‘lubb’ sound. It consists of four components: a low-frequency, indistinct vibration caused by ventricular contraction; a louder sound of higher frequency caused by closure of the mitral and tricuspid valves; a vibration caused by opening of the semilunar valves and early ejection of blood from the ventricles; and a low-pitched vibration produced by rapid ejection.
The second heart sound (S2) is shorter and higher pitched than the first, is heard as a ‘dupp’ and is produced by closure of the aortic and pulmonary valves.
The third heart sound (S3) is very faint and is caused by blood rushing into the ventricles.
The fourth heart sound (S4) is rarely audible in a normal heart but can be demonstrated on graphic records. It is short and of low frequency and intensity, and is caused by atrial contraction. The vibrations arise from atrial muscle and from blood flow into, and distention of, the ventricles.

Normal heart sounds. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991

  • muffled h. s. — the heart sounds are normal in outline but muffled, due usually to the presence of fluid between the heart and the stethoscope.
 
Wikipedia: heart sounds
Front of thorax, showing surface relations of bones, lungs (purple), pleura (blue), and heart (red outline). Heart valves are labeled with "B", "T", "A", and "P".First heart sound: caused by atrioventricular valves - Bicuspid/Mitral (B) and Tricuspid (T). Second heart sound caused by semilunar valves -- Aortic (A) and Pulmonary/Pulmonic (P).
Enlarge
Front of thorax, showing surface relations of bones, lungs (purple), pleura (blue), and heart (red outline). Heart valves are labeled with "B", "T", "A", and "P".

First heart sound: caused by atrioventricular valves - Bicuspid/Mitral (B) and Tricuspid (T).

Second heart sound caused by semilunar valves -- Aortic (A) and Pulmonary/Pulmonic (P).
Diagram showing relations of opened heart to front of thoracic wall. Ant. Anterior segment of tricuspid valve. A O. Aorta. A.P. Anterior papillary muscle. In. Innominate artery. L.C.C. Left common carotid artery. L.S. Left subclavian artery. L.V. Left ventricle. P.A. Pulmonary artery. R.A. Right atrium. R.V. Right ventricle. V.S. Ventricular septum.
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Diagram showing relations of opened heart to front of thoracic wall. Ant. Anterior segment of tricuspid valve. A O. Aorta. A.P. Anterior papillary muscle. In. Innominate artery. L.C.C. Left common carotid artery. L.S. Left subclavian artery. L.V. Left ventricle. P.A. Pulmonary artery. R.A. Right atrium. R.V. Right ventricle. V.S. Ventricular septum.

The heart sounds are the noises (sound) generated by the beating heart and the resultant flow of blood through it. This is also called a heartbeat. In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, which provide important information about the condition of the heart.

In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heart beat. These are the first heart sound (S1) and second heart sound (S2), produced by the closure of the AV valves and semilunar valves respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs and adventitious sounds, or clicks.

Heart murmurs are generated by turbulent flow of blood, which may occur inside or outside the heart. Murmurs may be physiological (benign) or pathological (abnormal). Abnormal murmurs can be caused by stenosis restricting the opening of a heart valve, causing turbulence as blood flows through it. Valve insufficiency (or regurgitation) allows backflow of blood when the incompetent valve is supposed to be closed. Different murmurs are audible in different parts of the cardiac cycle, depending on the cause of the murmur.


Normal heart sounds

First heart tone S1, the "lub"(components M1 and T1)

The first heart tone, or S1, is caused by the sudden block of reverse blood flow due to closure of the atrioventricular valves, mitral and tricuspid, at the beginning of ventricular contraction, or systole. When the pressure in the ventricles rises above the pressure in the atria, venous blood flow entering the ventricles is pushed back toward the atria, catching the valve leaflets, closing the inlet valves and preventing regurgitation of blood from the ventricles back into the atria. The S1 sound results from reverberation within the blood associated with the sudden block of flow reversal by the valves.

Second heart tone S2 the "dub"(components A2 and P2)

The second heart tone, or S2, is caused by the sudden block of reversing blood flow due to closure of the aortic valve and pulmonary valve at the end of ventricular systole, i.e beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta, aortic blood flow quickly reverses back toward the left ventricle, catching the aortic valve leaflets and is stopped by aortic (outlet) valve closure. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonary (outlet) valve closes. The S2 sound results from reverberation within the blood associated with the sudden block of flow reversal.

Splitting of the second heart sound

During inspiration, negative intrathoracic pressure causes increased blood return into the right side of the heart, yet some slowing of emptying from the left side. The increased blood volume in the right ventricle causes the pulmonary valve to stay open longer during ventricular systole. This causes an increased delay in the P2 component of S2 relative to the A2 component. During expiration, the positive intrathoracic pressure causes decreased blood return to the right side of the heart. The reduced volume in the right ventricle allows the pulmonary valve to close earlier at the end of ventricular systole, causing P2 to occur earlier, and "closer" to A2. It is physiological to hear a "splitting" of the second heart tone in younger people, during inspiration and in the "pulmonary area", i.e. the 2nd ICS (intercostal space) at the left edge of the sternum. During expiration, the interval between the two components normally shortens and the S2 sounds becomes merged.

If this splitting does not vary with inspiration, it is termed "fixed split S2" and is usually due to an atrial septal defect (ASD) or ventricular septal defect (VSD). The ASD or VSD creates a left to right shunt that increases the blood flow to the right side of the heart, thereby causing the pulmonic valve to close later than the aortic valve independent of inspiration/expiration.

Extra heart sounds

The rarer extra heart sounds are heard in both normal and abnormal situations.

Third heart sound S3

Rarely, there may be a third heart sound S3. The third heart sound or protodiastolic sound is not of valvular origin, as it occurs at the beginning of diastole just after S2. This sound occurs when the left ventricle is not very compliant, and at the beginning of diastole the rush of blood into the left ventricle suddenly is halted, resulting in a vibration of the ventricle and surrounding structures.

The third heart sound is normal in children and young adults, but disappears before middle age. Abnormal reemergence of this sound late in life indicates a pathological state, often a sign of a failing left ventricle as in dilated congestive heart failure (CHF). This sound is called a protodiastolic gallop, a type of gallop rhythm.

Fourth heart sound S4

The rare fourth heart sound S4 is sometimes audible in healthy children, but when audible in an adult is called a presystolic gallop. This gallop is a sign of a pathologic state, usually a failing left ventricle. This sound occurs just after atrial contraction ("atrial kick") and is the sound of blood being forced into a stiff/hypertrophic left ventricle. The combined presence of S3 and S4 is a quadruple gallop. At rapid heart rates, S3 and S4 may merge to produce a summation gallop.

Abnormal sounds

Aortic area, pulmonic area, tricuspid area and mitral area are the area where we auscultate the heart. Heart murmurs are produced as a result of turbulent flow of blood, turbulence sufficient to produce audible noise. They usually are heard as a whooshing sound. The term murmur only refers to a sound believed to originating within blood flow through or near the heart; rapid blood velocity is necessary to produce a murmur. Though not fully reliable, soft murmurs are less likely to reflect a serious, if any, health problem; loud murmurs essentially always reflect a problem. Yet most heart problems do not produce any murmur and most valve problems also do not produce an audible murmur.

The following paragraphs overview the murmurs most commonly heart in adults, adults who do not have major congenital heart abnormalities.

  • Regurgitation through the mitral valve is by far the most commonly heard murmur, sometimes fairly loud to a practiced ear, even though the volume of regurgitant blood flow may be quite small. Yet, though often obvious, probably about 20% of cases of mitral regurgitation, though obvious using echocardiography visualization, do not produce an audible murmur.
  • Stenosis of the aortic valve is typically the next most commonly heart murmur, a systolic ejection murmur. This is more common in older adults or in those individuals having a two, not a three leaflet aortic valve.
  • Regurgitation through the aortic valve, if marked, is sometimes audible to a practiced ear with a high quality, especially electronically amplified, stethoscope. Generally, this is a very rarely heard murmur, even though aortic valve regurgitation is not so rare. Aortic regurgition, though obvious using echocardiography visualization, usually does not produce an audible murmur.
  • Stenosis of the mitral valve, if severe, also rarely produces an audible, low frequency soft rumbling murmur, best recognized by a practiced ear using a high quality, especially electronically amplified, stethoscope.
  • Either regurgitation through, or stenosis of, the tricuspid or pulmonary valves essentially never produces audible murmurs.
  • Other audible murmurs are associated with abnormal openings between the left ventricle and right heart or from the aortic or pulmonary arteries back into a lower pressure heart chamber.
Gradations of Murmurs[1]
Grade Description
Grade 1 Very faint, heard only after listener has "tuned in"; may not be heard in all positions.
Grade 2 Quiet, but heard immediately after placing the stethoscope on the chest.
Grade 3 Moderately loud.
Grade 4 Loud, with palpable thrill.
Grade 5 Very loud, with thrill. May be heard when stethoscope is partly off the chest.
Grade 6 Very loud, with thrill. May be heard with stethoscope entirely off the chest.

As noted, several different cardiac conditions can cause heart murmurs. However, the murmurs produced often change in complex ways with the severity of the cardiac disease. An astute physician can sometimes diagnose cardiac conditions with some accuracy based largely on the murmur, related physical examination and experience with the relative frequency of different heart conditions. However, with the advent of better quality and wider availability of echocardiography and other techniques, heart status can be recognized and quantified much more accurately than formerly possible with only a stethoscope, examination and experience.

Clicks: With the advent of newer, non-invasive imaging techniques, the origin of other, so-called adventitial sounds or "clicks" has been appreciated. These are short, high-pitched sounds.

  • The atrioventricular valves of patients with mitral stenosis may open with an opening snap on the beginning of diastole.

Rubs: Patients with pericarditis, an inflammation of the sac surrounding the heart (pericardium), may have an audible pericardial friction rub. This is a characteristic scratching, creaking, high-pitched sound emanating from the rubbing of both layers of inflammated pericardium. It is the loudest in systole, but can often be heard also at the beginning and at the end of diastole. It is very dependent on body position and breathing, and changes from hour to hour.

There are a number of interventions that can be performed that alter the intensity and characteristics of abnormal heart sounds. These interventions can be performed to differentiate the different heart sounds and obtain a diagnosis of the cardiac anomaly that causes the heart sound. (See Heart murmur#Interventions that change murmur sounds.)

Inhalation pressure also causes an increase in the venous blood return to the right side of the heart. Therefore, right-sided murmurs generally increase in intensity with inspiration. The increased volume of blood entering the right sided chambers of the heart restricts the amount of blood entering the left sided chambers of the heart. This causes left-sided murmurs to generally decrease in intensity during inspiration.

With expiration, the opposite haemodynamic changes occur. This means that left-sided murmurs generally increase in intensity with expiration. Having the patient lie supine and raising their legs up to a 45 degree angle facilitates an increase in venous return to the right side of the heart producing effects similar to inhalation-increased blood flow.

Surface anatomy

The opening and closing of the valves is usually much less loud than the sound of the blood rushing through the valve and "colliding" with the subsequent barrier. Because of this, auscultation to determine function of a valve is usually not performed at the position of the valve, but at a downstream position where the listener can best hear the blood colliding after the valve is closed.

Pulmonary valve (to pulmonary trunk) second intercostal space left upper sternal border
Aortic valve (to aorta) second intercostal space right upper sternal border
Mitral valve (to left ventricle) fifth intercostal space lateral to left midclavicular line
Tricuspid valve (to right ventricle) fourth intercostal space lower left sternal border

Recording heart sounds

With the advent of electronic stethoscopes, it is now possible to conveniently record heart sounds. One electronic stethoscope manufactured by Thinklabs provides a port to output stethoscope sounds to an external recording device, such as a laptop or MP3 recorder. The same connection can then be used to listen to the recordings through the stethoscope headphones, allowing for faithful reproduction of low-frequency murmurs and other heart sounds.

See also

End Notes

  1. ^  "The Cardiovascular System." Bates, B. A Guide to Physical Examination and History Taking. 9h Ed. 2005.

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World of the Body. The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Heart sounds" Read more

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