Auscultation techniques.

The stethoscope

The many various heart sounds and murmurs heard in cardiac auscultation vary greatly in tone, pitch, and volume from one another, a variance which does not occur only between patients, but also between auscultatory sites upon the same patient. Heart sounds may also be confounded by respiratory sounds and external noises, especially in the prehospital environment. The best stethoscope therefore is not just one which is versatile enough to clearly pick up all of these frequencies when used correctly, but which also allows selective listening to one particular sound, such as when seeking the presence of S4 in a chest pain patient. For these reasons stethoscopes composed of both a bell and diaphragm are often recommended for cardiac auscultation as these two heads are used for different pitches of sound. (Chizner, 2008; Shindler, 2007).

• The bell chestpiece is used to pick up low frequency sounds, such as the dull gallops of S3 and S4.
• To use the bell correctly it must be applied to the skin with very little pressure - only enough weight to seal the bell against the skin and exclude external noises.
• Heavy pressure of the bell creates an improvised diaphragm with the skin, quickly eliminating low frequency sounds. This technique may be used purposefully, such as to distinguish between a late S4 sound from a split S1; under heavy pressure the S4 sound will disappear, whilst the stronger, higher pitched split S1 component will not.
• The diaphragm chestpiece  will pick up high frequency sounds, such as harsh murmurs, systolic clicks, and the squeak of pericardial rub.
• Converse to the bell, the diaphragm requires firm pressure to accentuate high pitched sounds whilst filtering out lower pitched vibrations.
• Some stethoscopes permit use of the diaphragm for both low and high pitched sounds by altering the pressure applied; this technique saves lifting the chestpiece from the patient to auscultate different frequencies in the same point. Again, a very light pressure is required for 'bell' function, but in this situation the low frequency sounds will be heard at greater volume due to the increased size of the chestpiece. 

(3M, 2012; Chizner, 2008; Shindler, 2007).

Timing and preparation

First and foremost, cardiac auscultation must not delay any emergent assessments, treatment, or analgesia; in the prehospital setting it is an adjunct assessment, not a primary one, and should await the right time. Judgement and clinical common sense will prevail here, but in a chest pain case for example this may be once all primary and secondary management actions including IV access, morphine administration, and 12-lead ECG have been completed. The following are considerations when preparing for cardiac auscultation in the prehospital setting.

• Cardiac auscultation cannot be performed over clothing as through fabrics the softer sounds and lower frequencies are inevitably lost, and contact with the clothing itself will produce interference as well as fail to exclude external noises. 
• Where possible ensure a warm environment, which in winter may mean leaving auscultation until within the warmth of the ambulance, or doing it on scene before clothing the patient again to go outside. Cold temperatures are not only unpleasant for the patient, but the muscle tremors of shivering will create extraneous noise on auscultation.
• It is a good idea to time cardiac auscultation to occur after 12-lead ECG as the chest will need to be bared for both procedures, eliminating the need to uncover the patient on two occasions.
• The chestpiece of the stethoscope should be warmed within the hand prior to use.
• Ensure that the room is as quiet as possible. This may mean asking residents to pause in conversations and to turn off the television for a few minutes, or if noises are unavoidable auscultation may be better performed once in the ambulance vehicle prior to starting the engine and air conditioning.

Patient consent and dignity

Invented in 1816 by René Laennec, the stethoscope was first formed from rolled up paper for reasons of modesty when auscultating women. Maintenance of patient dignity and comfort remains a primary concern today, and consent should be obtained specifically for cardiac auscultation even if it has been gained for 12-lead ECG, especially in women. The procedure is, literally, a hands-on one, whereas in 12-lead ECG for comparison the electrodes are rapidly applied and the chest may then be lightly covered during acquisition.

• As always, explain the procedure and why it is being done. Advise the patient that the stethoscope will be applied to the central and left sides of the chest, and that the chest will need to be uncovered. 
• Always ensure that auscultation is done in a private environment, and that other persons present in the room are asked to leave unless the patient consents for them to remain. If this is not possible then auscultation may be done as soon as the patient is in the ambulance vehicle instead, with curtains drawn and with the engine turned off.
• When auscultating at the apex of the heart, ask female patients to lift their left breast for you. If they are unable to assist then the breast may be moved using the back of your other hand. 
• It may be possible to lay a towel across the patient, using the hand and forearm to raise this off the chest as needed to reduce exposure. 

Areas of auscultation

The traditional four main areas of cardiac auscultation are sites at which the four valves are each best heard, and thusly were named after those valves, but it is better practice to refer to these sites by their anatomical locations as heart sounds frequently radiate to other locations. To these four sites other locations have since been added, and many texts recommend five or six sites of auscultation. The list following applies to the illustration to the right, and is for the five common auscultatory sites; when a sixth site is added, this is at the fifth left intercostal space, sternal border:

1.     Second right intercostal space, sternal border (aka aortic area)

In this area murmurs and dysfunction of the aortic valve are likely to be projected, not because the area overlies the aortic valve, but due to the direction of blood flow through the aorta as it leaves the left ventricle. 

2.     Second left intercostal space, sternal border (aka pulmonic area)

Sounds from the pulmonary  valve are projected to this point; due to the lower pressures, such sounds are usually quieter than those of the aorta. 

3.     Third left intercostal space, sternal border (aka Erb's point) 

At this site S2 and the pulmonic and aortic valves may directly be auscultated, especially if the patient leans forward. The return of blood to the left atrium through a failing mitral valve may also be auscultated, indicating mitral regurgitation.

(Srodulski, n.d.)

4.     Fourth left intercostal space, sternal border (aka tricuspic area) 

The tricuspid valve and S1 may be auscultated here, as this point overlies the right ventricle. This is also the best point to auscultate S3 and S4 of right ventricular origin, and to determine respiratory effect upon heart sounds.

5.     Fifth left intercostal space, mid-clavicular line at the cardiac apex (aka mitral area)

The apex is the best point to auscultate left ventricular sounds, such as left-sided S3 and S4, and dysfunction of the aortic valve. Auscultation of the apex is improved if the patient is rolled onto their left side to bring the heart closer to the chest wall.

(Chizner, 2008; Hanifin, 2010).

Systematic auscultation

Systematic cardiac auscultation involves beginning at the base in the second right intercostal space, by the sternal border, and first identifying the first and second heart sounds and becoming familiar with the rhythm and sound of the heartbeats. This should initially be done whilst palpating the carotid pulse which immediately follows S1, allowing identification of the first and second heart sounds even in accelerated heart rates. (Shindler, 2007). The assessment then continues with 'inching' from one auscultatory site to the next according to the above diagram. At each site the following should be assessed in turn: S1, S2, presence of S3 or S4, presence of any clicks or murmurs. It is recommended to listen at each point to low and high frequency with both bell and diaphragm, which may be done using the pressure 'tuning' method described above, or by switching the chestpiece to use first one and then the other. (Chizner, 2008; Walsh, O'Rourke, & Shaver, 2011).

The following video provides an excellent demonstration of systematic cardiac auscultation.

(ProfHeaslip, 2011).

Describing findings

Details used to describe heart sounds for handover and documentation may include the identity, location, volume, quality, and timing of the sound, and any response to treatment or to changes in posture or respiration. For example, the handover for a responsive cardiogenic chest pain case may include the description of "a quiet S4 initially heard at the apex only during held expiration, but which has resolved over the course of treatment". Descriptions become more complex when describing heart murmurs, as will be outlined later in this course.

Next: Heart sounds S1 and S2.

References

3M. (2012). Learn more about auscultation and 3M™ Littmann® Stethoscopes. Retrieved 21 May, 2012 from http://solutions.3m.com/wps/portal/3M/en_US/3M-Littmann/stethoscope/customer-service/help/

Chizner, M. (2008). Cardiac auscultation: rediscovering the lost art. Current Problems in Cardiology, 33(7), 326-408. 

Hanifin, C. (2010). Cardiac auscultation 101: a basic science approach to heart murmurs.  Journal of the American Academy of Physician Assistants, 23(4), 44-48. Retrieved from http://media.jaapa.com/documents/13/cme_auscultation_3131.pdf

Lilly, L. & Jung, H. (2011). The cardiac cycle: mechanisms of heart sounds and murmurs. In L. Lilly (Ed.), Pathyphysiology of Heart Disease. (5th ed.). Baltimore, Maryland: Lippincott Williams & Wilkins.

ProfHeaslip. (2011, Jun 7). 9-Auscultation of heart sounds [Video file]. Retrieved from http://www.youtube.com/watch?v=83CBjj9dMRc

Shindler, D. (2007). Practical cardiac auscultation. Critical Care Nursing Quarterly, 30(2), 166-180.

Srodulski, K. (n.d.). Cardiac auscultation points [Image]. In C. Hanifin. (2010). Cardiac auscultation 101: A basic science approach to heart murmurs. Journal of the American Academy of Physician Assistants, 23(4), 44-48. Retrieved fromhttp://media.jaapa.com/documents/13/cme_auscultation_3131.pdf

Uazman, A., Asghar, O., Khan, S., Hayat, S., & Malik, R. (2010). Cardiac auscultation: an essential clinical skill in decline. British Journal of Cardiology, 17(1), 8-10.

Walsh, R., O'Rourke, R., & Shaver, J. (2011). The history, physical examination, and cardiac auscultation. In V. Fuster, Walsh, R., & Harrington, R. (Eds.), Hurst's The Heart. (13th ed.). New York, NY: The McGraw-Hill Companies, Inc.