INTRODUCTION:

Auscultation is a method of listening to the sound of the body employing directly using ear or a stethoscope to determine or evaluate the duration, frequency, intensity and sometime the quality in the sound produced by an internal body organ. Auscultation of heart could help physician to diagnose many cardiac abnormalities using the stethoscope¹. The stethoscope can detect from low frequency to the high frequency of the heart sounds, however, hearing the heart sound should be done in quiet environment or low ambient noise to ensure that process attempt a possible disease. In this review article we know about the auscultate methods, the heart sounds, and signal, heart murmurs sounds, splitting of sounds and abnormality in heart.

Auscultation of heart should be taken up only after the precordium has been thoroughly examined. Many students do not give enough time to the examination of arterial and venous pulses and the precordium, and directly auscultate the heart to diagnose heart diseases^2,3. Auscultation is a method of listening to the sound of the body employing directly using ear or a stethoscope to determine or evaluate the duration, frequency, intensity, and sometime the quality in the sound produced by internal body organ. Cardiac auscultation taught by Laennec was a great success, and in subsequent years become a crucial component of cardiac physical examination, especially in times of important diffusion of rheumatic valvopathies.

Methods of Auscultation of Heart Sound:

Before one auscultate the heart, one should have some idea of what abnormalities one expects to detect with the stethoscope. Before one auscultate the heart, one should have some idea of what abnormalities one expects to detect with the stethoscope. With the help of the stethoscope, auscultate the different areas in the following sequences: - mitral area, pulmonary area, aortic area, and tricuspid area⁴. The diaphragm of the stethoscope should be placed firmly on different areas to hear the heart sounds.

In each area, the following points should be noted during auscultation.

First(s1) and second(s2) heart sounds: -

Note their quality, intensity, duration and character. S1 is heard better on the mitral area, and S2 is heard better over pulmonary and aortic area.

Fig 1: Cardiovascular examination

a. Other sounds (if present).

· Third heart sound (s3)

· Fourth heart sound (s4)

· Murmurs

· Opening snap

· Ejection click

If murmur is present, note the site of origin, timing, character, radiation and its relation with respiration.

Heart sound are studied by three methods.

A. By using stethoscope.

B. By using microphone.

C. By using phonocardiogram.

A. By Stethoscope:

First and second heart sounds are heard on the Auscultation areas, by using the stethoscope. The chest piece of the stethoscope is placed over four areas on the chest, which are called auscultation area.

Auscultation area: -

With the help of the stethoscope, auscultate the different areas in the following sequence: -Mitral area, Pulmonary area, Aortic area, and Tricuspid area^5,6. The diaphragm of the stethoscope should be placed firmly on different areas to hear the heart sounds.

1. Mitral area (Bicuspid area) or (M):

This area corresponds to the apex beat of the heart. The first heart sound is best heard over the mitral area. Normally, this is present in the left fifth intercostal space half an inch medial to the midclavicular line. i.e 5^th intercostal space about 8-10 cm from the midsternal line. It is also called apex beat area because apex beat is felt in this area⁷. Apex beat is the thrust (pushing forcefully) of the apex of ventricles, against chest wall during systole.

2. Pulmonary area (P):

This area is half an inch in diameter with its centre in the left second intercostal space close to the parasternal line, i.e. it lies to the left of the sternum in the second intercostal space⁸. Sound produced by the closure of pulmonary valve (second heart sound) is heard well on this area.

3. Aortic area (A):

This area is half an inch in diameter with its centre in the right second intercostal space close to the parasternal line, i.e. It lies to the right of the sternum in the second intercostal space^9,10. On this area, the sound produced by the closure of aortic valve (second heart sound) is heard well.

B. By microphone:

A highly sensitive microphone is placed over the chest. The heart sounds are amplified by means of an amplifier and heard by using a loudspeaker¹¹. First, second and third sounds are heard by this method.

C. By phonocardiogram:

Phonocardiography is the technique used to record the heart sounds. Phonocardiogram is the graphical record of heart sounds. It is done by placing an electronic sound transducer over the chest. This transducer is connected to a recording device like polygraph^12,13. All four heart sounds can be recorded in phonocardiogram. It helps to analyze the frequency of the sound waves.

· Appearance of heart sounds in phonocardiogram:

In phonocardiogram, the heart sounds are recorded in the following manner: -

· First heart sound:

First heart sound is recorded as single group of waves. The waves are of small amplitude to start with Later, the amplitude rapidly rises and falls to form crescendo and diminuendo series of waves. About 9 to 13 waves appear.

· Second heart sound:

Second heart sound appears as single group of waves, which have same amplitude¹⁴. About 4 to 6 waves are recorded.

· Third heart sound:

Third heart sound is found in phonocardiogram with only 1 to 4 waves grouped together.

· Fourth heart sound:

Mostly, the fourth heart sound merges with first heart sound^15,16. If it appears as separate form, it has 1 to 2 waves with very low amplitude.

Heart sounds are the sounds produced by mechanical activities of heart during each cardiac cycle.

Different heart sounds:

Four heart sound are produced during each cardiac cycle. First and second heart sounds are called classical heart sounds and are heard by using the stethoscope¹⁷. These two sounds are more prominent and resemble the spoken words “LUB”, or (LUBB) and “DUBB” or (DUB)’, respectively.

Importance of heart sounds:

Study of heart sound has important diagnostic value in clinical practice because alteration in the heart sounds indicates cardiac diseases involving valves of the heart.

First heart sound (s1).

The first heart sound represents the beginning of the systole. It is produced during isometric contrition period and earlier part of ejection period.

Causes of first heart sound:

Major cause for first heart sound is the sudden and synchronous (simultaneous) closure of atrioventricular valves¹⁸. Turbulence created in the blood due to ventricular contraction. However, some other factors are also involved.

Four type of factors are responsible for the production of the first heart sound.

1. Valvular Factor:

Synchronous closure of atrioventricular valves set up the vibrations in the valvular leaflets and chordae tendineae^19,20. These vibrations are mainly responsible for the production of the first heart sound.

2. Vascular Factor:

Rush of blood from the ventricles into aorta and pulmonary artery during ejection period is also responsible for the production of the first heart sound.

3. Muscular Factor:

Myocardial tension and the contrition of ventricular muscle during isometric contraction and the ejection periods also add to the production of the heart sound.

4. Atrial Factor:

Vibration produced by the atrial systol also play a role in the production of the first heart sound.

Significance of first heart sound:

It signifies the beginning of the ventricular systol and AV valve closure.

(a). Accentuation of first heart sound.

· Exercise

· Hyperkinetic circulatory states like anemia and beriberi.

· Hypertension

(b).Diminution of first heart sound.

· Shock

· Acute myocardial infection

· Constrictive pericarditis

· Pericardial effusion

· Cardiomyopathy (advanced stage)

· Obesity

· Emphysema.

Causes of second heart sound:

Second heart sound is produced due to the sudden and synchronous closure of the semilunar valve ²¹. Rushing of blood into the ventricles due to opening of AV valves also contributes.

Characteristics of second heart sound:

Second heart sound is a short, sharp and high-pitched sound. It resembles the spoken word ‘DUBB’ or ‘DUB’²². Duration of second heart sound is 0.10 to 0.14 sec or about 0.12 sec. Its frequency is 50 cycles/sec or 50 Hz.

Third heart sound (s3):

Third heart sound is usually not heard in many healthy individual. Sometime it may be heard in children and in young adults. It is usually heard in conditions in which the circulation becomes hyperkinetic. The third sound can arise from either side of the heart, but usually it arises in the left ventricle^23,24. Usualiy, the third heart sound is inaudible if stethoscope is used and it can be heard only by using microphone.

Causes of third heart sound:

Third heart sound is produced by rushing of blood into ventricles and vibration set up in the ventricular wall during rapid filling phase. It may also be due to vibrations set up in chordae tendineae²⁵. Rebound fencing of cusp of the valve and chordae of the respective valve due to vigorous elongation of the ventricle caused by rapid inflow of blood also contributes to this.

1. It is an important sign of heart failure; the atrial pressure is increased and early filling of the ventricle is rapid.

2. It may be heard shortly after myocardial infarction or in disease where the distensibility of the ventricular muscles is altered²⁶. The sound arises from vibration in the atrioventricular valve structures and in the ventricular muscle.

Condition when third heart sound becomes auricle by stethoscope:

Third heart sound can be heard by stethoscope in children and athletes. Pathological conditions when third heart sound becomes loud and audible by stethoscope are aortic regurgition, cardiac failure and cardiomyopathy with dilated ventricles.

When third heart sound is heard by stethoscope, the condition is called triple heart sound (see below)^27,28. Third heart sound is usually heard best with the bell of stethoscope placed at the apex beat area, when the patient is in left leteral decubitus (lying on left side) position.

Fourth heart sound (s4):

Normally, the fourth heart sound is an inaudible sound. It becomes audible only in pathological conditions. It is studied only by graphical recording i.e by phonocardiography²⁹. This sound is produced during atrial systole (late diastole) and it is considered as the physiologic atrial sound. It is also called atrial gallop or presystolic gallop.

This is also called the atrial sound, because it is produced during atrial contraction. It is not heard in normal individuals^30,31. Presence of the fourth heart sound is always considered abnormal.

Characteristics of fourth heart sound:

It occurs just before the first sound, that is late in the diastole ³². Fourth heart sound is short and low-pitched sound. Duration of this sound is 0.02 to 0.04 second. Its frequency is 1 to 4 cycles/second or Hz.

Fourth heart sound and ECG:

Fourth heart sound coincide with the interval between the end of ‘P’ wave and the onset of ‘Q’ wave.

Significance of fourth heart sound:

1. It always indicates increased stiffness or non-compliance of the ventricles. Therefore, when a bolus of blood is delivered into the ventricle by atrial contraction^33,34, it facilitates a sudden increase of pressure in the ventricle.

2. It is seen in left ventricular hypertrophy due to hypertension, myocardial infarction, pulmonary embolism and pulmonary hypertension.

Triple heart sound:

This consists of three heart sounds: - the first and second heart sound, and the third one can be either the third or fourth heart sound. The triple rhythm associated with a normal heart may not be a serious one, but if it is present with a definate cardiac pathology³⁵, it may signify a serious condition.

C. SPLITTING IN HEART SOUNDS:

Splitting of first heart sound: - Splitting of first heart sound is also known as “reduplication of first heart sound”. First heart sound is split when the atrioventricular valves do not close simultaneously (asynchronous closure) i.e mitral valve close just before the tricuspid valve but this splitting cannot be detected by auscultation³⁶, because both the component (mitral and tricuspid) are very low-pitched and merge into each other.

Soft first heart sound: - Heart sound becomes soft when intensity of sound decreases. A soft first heart sound is heard in low blood pressure, severe heart failure, myocardial infarction and myxoedema.

Loud or accentuated first heart sound: First heart sound becomes louder or accentuated (becoming prominent) in condition like mitral stenosis Wolff-Parkinson-white syndrome and acute rheumatic fever^37,38. It is loud in patients with thin chest wall also.

Cannon sound: Cannon sound refers to the loud first heart sound that is heard intermittently. It is heard in ventricular tachycardia and complete atrioventricular block.

Physiological splitting:

It occurs during deep inspiration. Normally, aortic valve closes prior to the closure of pulmonary valve. Interval between the two valves widens during inspiration and narrows during expiration³⁹. Increased negative intra thoracic pressure during deep inspiration increases lung expansion and venous return into right atrium.

Fig. 2 Cardiovascular splitting

Pathological splitting:

Splitting of second heart sound occurs during the pathological conditions such as pulmonary stenosis, right bundle branch block and right ventricular hypertrophy.

Splitting of second heart sound is due to the gap between the aortic and pulmonary components. It is easy to detect because aortic and pulmonary valve closure sounds are high-pitched and can be separated.

D. MURMUR SOUND:

Cardiac murmur is the abnormal or unusual heart sound. It is also called abnormal heart sound or cardiac bruit. Cardiac murmur is heard by stethoscope, along with normal heart sounds. Cardiac murmur is heard by placing chest piece of stethoscope over the auscultatory area of the valve. Sometime, the murmur is felt by palpation as ‘thrills’. In some patients, murmur is heard without any aid, even at a distance of few feet away from the patient.

Causes of murmur:

Cardiac murmur is produced because of change in the pattern of blood flow. Normally, blood flows in streamline through the heart and blood vessels. However, during abnormal conditions like valvular disease, the blood flow become turbulent. It produces the cardiac murmur⁴⁰.

Hart murmurs are related to valve disease are typically diagnosed by examining the spectral characteristics of the heart sound with additional information such as amplitude and timing.

Fig. 3: Systolic heart murmurs come in four varieties.

CONCLUSION:

In this article we studied about the auscultation of heart sounds with the help of stethoscope, microphone, and phonocardiogram. Different auscultatory areas like mitral area, tricuspid area, pulmonary area and aortic area are studied for proper auscultation of heart sounds with the help of stethoscope. The heart sound signal presents in a graphical form in this case using spectrogram or phonocardiogram provide details of amplitude and frequency value during measurement of heart sounds. Compared to the conventional tools. With the help of auscultation we also know about the duration of different heart sounds. There are four heart sound heard with the help of stethoscope and microphone, their name is s1, s2, s3, and s4. However, in this system the s3 and s4 sound are abnormal sound which is generally not heard in normal and healthy human. It is heard in abnormal condition of heart. A murmur sound is also heard with the help of stethoscope. In this article we also studied about the different disorder related to the heart. Digital stethoscope and intelligent phonocardiography can help the doctor to achieve a correct diagnosis offering further research perspective in this area.

REFERENCE:

1. Pelech AN, Pasterkamp H, editors. R.A.L.E. Heart sounds and murmurs. Computer auscultation program. Winnipeg (Manitoba, Canada). 7 Pixsoft Inc; 1992.

2. Tavel ME, Brown DD, Shander D. Enhanced auscultation with a new graphic display system. Arch Intern Med. 1994;154(8):893 – 8.

3. Selig MB. Stethoscopic and phonoaudio devices: historical and future perspectives. Am Heart J. 1993;126:262.

4. Mangione S, Neiman LZ, Gracely E, et al. The teaching and practice of cardiac auscultation during internal medicine and cardiology training: a nationwide survey. Ann Intern Med. 1993; 119:47 – 54.

5. Canent RV. Recognizing common innocent heart murmurs in infants and children. Mo Med. 1986; 83(9): 621.

6. Fogel DH. The innocent systolic murmur in children: a clinical study of its incidence and characteristics. Am Heart J 1960;59:844.

7. Geva T, Hegesh J, Frand M. Reappraisal of the approach to the child with heart murmurs: is echocardiography mandatory? Int J Cardiol. 1988; 19: 107.

8. Snider AR. Echocardiography in pediatric heart disease. Littleton (MA)7 Year Book Medical Publishers; 1990.

9. Smythe JF, Teixeira OHP, Vlad P, et al. Initial evaluation of heart murmurs: is echocardiography mandatory? Peds. 1990; 86: 497 – 500.

10. Hurrell DG, Bachman JW, Feldt RH. How to evaluate murmurs in children. Postgrad Med. 1989; 86(2): 239.

11. Constant J, editor. The stethoscope. In: Bedside cardiology. 4th edition. London7 Little, Brown and Company; 1993. p. 124.

12. Rosenthal A. How to distinguish between innocent and pathologic murmurs in childhood. Pediatr Clin North Am 1984;31:1229.

13. Grewe K, Crawford MH, O’Rourke RA. Differentiation of cardiac murmurs by dynamic auscultation. Curr Probl Cardiol. 1988; 13(10): 669.

14. Still GR. Common disorders and diseases of childhood. London7 Frowde, Hodder and Stoughton; 1915.

15. McKusick VA, editor. Cardiovascular sound in health and disease. Baltimore (MD)7 Williams and Wilkins; 1958. p. 244.

16. Harris TN, Friedman S, Tuncali MT, et al. Comparison of innocent cardiac murmurs in high output states. Pediatrics. 1964; 33: 341 – 56.

17. Stein PD, Sabbah HN. Aortic origin of innocent murmurs. Am J Cardiol. 1977; 39: 665.

18. Perry LW, Ruckman RN, Shapiro SR, et al. Left ventricular false tendons in children: prevalence as detected by 2-dimensional echocardiography and clinical significance. Am J Cardiol. 1983; 52: 1264 – 6.

19. Rosenthal A. Office maneuvers for evaluating children’s heart murmurs. Consultant 1986; 26(6):147.

20. Martins L, Van Zeller P, Roch-Goncalves F, et al. Morphology, prevalence and clinical significance of left ventricular false tendons in adults. Acta Cardiol. 1988; 93: 245 – 9.

21. Danilowicz DA, Rudolph AM, Hoffman JI, et al. Physiologic pressure differences between the main and branch pulmonary arteries in infants. Circulation. 1972; 45: 410 – 9.

22. Stapelton JF, El-Hajj MM. Heart murmurs simulated by arterial bruits in the neck. Am Heart J. 1961; 61: 178.

23. Perloff JK, editor. Innocent murmurs. In: The clinical recognition of congenital heart disease. Philadelphia7 WB Saunders; 1972. p. 11 – 3.

24. Nelson WP, Hall RJ. The innocent supraclavicular arterial bruit—utility of shoulder maneuvers in its recognition. N Engl J Med. 1968; 278: 778.

25. Kawabori I, Stevenson JG, Dooley TK, et al. The significance of carotid bruits in children. Am Heart J. 1979; 98: 160 – 7.

26. Nellen M, Gotsman MS, Vogelpoel L, et al. Effects of prompt squatting on the systolic murmur in idiopathic hypertrophic obstructive cardiomyopathy. BMJ. 1967; 3: 140 – 3.

27. Potain SC. Des mouvements et des bruits qui se passent dans les veines jugulaires. Bull Mem Soc Med Hop Paris 1867;4:3.

28. Cary FH. Symptomatic venous hum. Report of a case. N Engl J Med. 1961; 264: 869.

29. Cutforth R, Wiseman J, Sutherland RD. The genesis of the cervical venous hum. Am Heart J 1970;80:488.

30. Tabatznik B, Randall TW, Hersch C. The mammary souffle of pregnancy and lactation. Circulation. 1960; 22: 1069.

31. Hanna, I.R. and M.E. Silverman, A history of cardiac auscultation and some of its contributors. Am J Cardiol. 2002. 90(3): 259-67.

32. Constant, J., Bedside Cardiology. 5th Edition ed. 1999: Lippincott Williams and Wilkins.

33. Tavel, M.E., Cardiac auscultation: a glorious past--and it does have a future! Circulation. 2006; 113(9): 1255-9.

34. Ghosh, A., Mayo Clinic Internal Medicine Review. 8th Edition ed. 2010: Mayo Clinic Scientific Press. 1130.

35. Bickley, L.S., Bates' Guide to Physical Examination and History Taking. 10th Edition ed. 2009, Philadelphia: Wolter Kluwer Lippincott Williams and Wilkins.

36. Delgado-Trejos, E., et al., Digital auscultation analysis for heart murmur detection. Ann Biomed Eng. 2009; 37(2): 337-53.

37. Debbal, S.M. and F.Bereksi-Reguig, Frequency analysis of the heartbeat sounds. Biomedical Soft Computing and Human Sciences. 2008; 13(1): 85-90.

38. Naseri, H. and M.R. Homaeinezhad, Detection and boundary identification of phonocardiogram sounds using an expert frequency-energy based metric. Ann Biomed Eng. 2013; 41(2): 279-92.

39. Arnott, P.J., G.W. Pfeiffer, and M.E. Tavel, Spectral analysis of heart sounds: relationships between some physical characteristics and frequency spectra of first and second heart sounds in normals and hypertensives. J Biomed Eng. 1984; 6(2): 121-8.

40. Martínez-Alajarín, J. and R. Ruiz-Merino, Efficient Method for Events Detection in Phonocardiographic Signals. SPIE Proceedings. 2005; 5839: 398-409.

41. Ahlstrom, C., et al., Feature extraction for systolic heart murmur classification. Ann Biomed Eng. 2006; 34(11): 1666-77.

Received on 08.12.2023 Modified on 09.03.2024

Asian J. Res. Pharm. Sci. 2024; 14(2):149-154.

DOI: 10.52711/2231-5659.2024.00023