Cardiac auscultation: the past, present and future

Cardiac auscultation is a critical part of the clinical examination. In this review we discuss the conventional approach to teaching and using the skill of cardiac auscultation. We then consider how recent technological advances may improve the teaching and implementation of this essential clinical skill.

The past: a historical perspective

The earliest description of the heart sounds comes from William Harvey’s De Motu Cordis in 1628, in which he likened the heart sounds to “two clacks of a water bellows to raise water”, but it was not until Laennec invented the stethoscope in 1816 that cardiac auscultation superseded percussion and direct auscultation. Laennec proposed the use of “a cylinder of wood, perforated in its centre longitudinally, by a bore three lines in diameter, and formed so as to come apart in the middle”; this he termed the cylinder or stethoscope. This was followed in 1819 by his landmark work De l’auscultation médiate ou traité du diagnostic des maladies des poumons et du coeur (On mediate auscultation or treatise on the diagnosis of the diseases of the lungs and heart), through which he achieved widespread recognition. The art of cardiac auscultation developed considerably during the nineteenth century and is now an essential component of the clinical examination. 

Present: traditional teaching methods

Traditionally, cardiac auscultation has been taught best at the bedside during clinical undergraduate training and in preparation for postgraduate membership examinations. It is an essential component of the clinical examination, but like most clinical skills requires repetition¹ and clinical experience to make an accurate diagnosis. Indeed, prior to the advent of echocardiography, physicians were totally reliant on their stethoscope and auscultatory skills to accurately diagnose and characterise cardiac murmurs. 

The traditional clinical teacher will maintain that there is no substitute for clinical bedside teaching, while the modern educationalist will opt for multimedia applications, audio CDs and patient simulators.^2,3 We would support the former, as evidenced by the decline in skills among medical graduates; cardiac auscultation, once the hallmark of an expert clinician, is rapidly becoming a lost art.⁴ The importance of cardiac auscultation cannot be underestimated and it remains an essential skill at the bedside, which, when performed well, can avoid the potential of ‘over-investigating’ patients and causing unnecessary anxiety. However, as many as three-quarters of American interns and two-thirds of cardiology trainees no longer receive formal teaching in cardiac auscultation.⁵ Of concern, several studies have reported an apparent lack of ability of interns to correctly diagnose a cardiac murmur, which we have reviewed recently.⁶ If this decline is related to lack of clinical exposure and deficiencies in current teaching methods, can this be rectified? 

Modern approaches

Several studies have reported an improvement in diagnostic skills with the use of various educational aids and methods. A recent study of third-year medical students found that the use of a computer-based teaching application increased their ability and confidence in detecting cardiac murmurs and added heart sounds.⁷ Similarly, another study found that the use of interactive CD-ROMs was associated with an improvement in auscultation skills.⁸ A group based at University of California, Los Angeles compared the use of a virtual patient examination (VPE) with a conventional teaching model in third-year medical students and found that VPE-based teaching resulted in a higher level of competency and long-term retention of knowledge of cardiac auscultation.⁹ The use of web-based resources, in addition to clinical training, has also been proposed in two separate studies.^10,11 The Mayo group reported an improvement in auscultation following attendance at a patient-centred teaching conference designed to improve such skills and taught by a master auscultator.¹² These data suggest that a combined approach, which maintains clinical exposure, utilising clinical experience, but incorporates technological innovation to reinforce learning, may be the best way forward.

Patient simulators

Patient simulators first made their debut at the American Heart Association (AHA) scientific sessions in 1968. Nicknamed Harvey after Dr W Harvey Procter, this sophisticated mannequin is able to display a number of cardiovascular indices including blood pressure (by auscultation), jugular venous pulse waveforms and arterial pulses, precordial impulses and auscultatory findings in the four classic areas (synchronised with the pulse and varying with respiration).¹³ Harvey is capable of simulating a spectrum of cardiac disease by varying blood pressure, breathing, pulses, normal heart sounds, and murmurs. Harvey underwent rigorous testing as an educational model with pilot studies first reporting promising results in 1980.¹⁴ A National Heart, Lung and Blood Institute (NHLBI)-funded study in 1987 found that senior medical students who had trained with Harvey performed significantly better than their peers, who had only clinical training.¹⁵ Harvey has since undergone several modifications and remains an important learning resource for healthcare professionals and trainees. Several other simulators have since followed the advent of Harvey. 

The future

With advances in technology, there has been considerable development of the traditional stethoscope and this has allowed us to overcome some of the previous acoustic limitations when using traditional stethoscopes. Electronic stethoscopes have the ability to amplify the heart sounds, filter sound frequency and eliminate background noise. Furthermore, a key to reinforcing teaching by the bedside, newer generation models are capable of storage and playback of heart sounds away from the patient through an external source or computer. The idea of combining such a stethoscope with computer software that could visualise the murmur and heart sounds as a means of facilitating undergraduate teaching was proposed several years ago.¹⁶ 

There are, however, very little published data comparing conventional and electronic stethoscopes. An early study in 1998 comparing some of the more primitive electronic stethoscopes with standard devices, concluded that the acoustic stethoscopes were preferable, however, they proposed that an ideal device would feature a combination of both.¹⁷ More recently, a Norwegian study randomised third-year medical students to either a traditional or an electronic stethoscope (Welch Allyn) and found no difference in terms of diagnostic accuracy when assessed by a cardiac auscultation test.¹⁸ A Danish study comparing a standard stethoscope with a ‘cardiology’ stethoscope also found no difference.¹⁹ Our own experience with electronic stethoscopes when teaching medical students has been a positive one based primarily on the ability to amplify sounds and reduce background noise. The ability to record the abnormal auscultatory findings and immediate facility to replay that sound has been particularly useful. 

The most recent developments that may benefit day-to-day clinical practice include the European launch of the 3M Littmann 3200 electronic stethoscope, which has the ability to transmit heart sounds via Bluetooth technology. This technology has Food and Drug Administration (FDA) approval in the USA and works in conjunction with software (Zargis Cardioscan^TM), which is able to accurately interrogate and analyse heart sounds and murmurs. Using sophisticated algorithms, the software has been shown to predict whether a murmur is clinically significant based on AHA class I murmur criteria.²⁰ We are currently conducting the first European clinical trial of this system to determine its accuracy in identifying innocent and pathological murmurs in real-world clinical practice in adult and paediatric populations. We believe this technology represents a major innovation in cardiac auscultation technology and such a device would be an invaluable screening tool and diagnostic aid in the settings of primary care and pre-op clinics, where often murmurs may be either missed or inappropriately investigated. Furthermore, the ability to digitally store these data may also allow the clinician to monitor and compare murmur intensity over time, and could prove useful in monitoring valvular disease, although this remains to be proven. 

With regard to teaching and examining, 3M are about to introduce StethED, software that has been developed on Android technology but is now being transposed to the iPhone and Blackberry. Essentially, 3200s are linked via Bluetooth to the smartphone and the ‘teacher’ indicates which stethoscope is to act as the teacher, and which are the students. All individuals will use their stethoscope to auscultate and the sounds will be gathered. This will enable the examiner not only to ascertain whether the student has placed the stethoscope correctly on the praecordium and, hence, acquired the correct sounds, but also whether the student has interpreted the sounds correctly. Thus, the student can no longer ‘hide’ behind an inability to ‘hear’ the murmur and, for examination purposes, it will allow a standardised approach with a ‘listening examiner’ being able to confirm or refute the auscultatory findings exactly at the time of examination.

Conclusion

Many factors have conspired to limit adequate teaching and maintenance of cardiac auscultation skills. Indeed the requirements and expectations of junior doctors, with regard to auscultation, are much lower now than in previous generations. While technological advancements, such as echocardiography, may well have contributed to the demise of cardiac auscultation, technology in the form of integrated electronic auscultation may well revive its place in clinical medicine²¹.

Conflict of interest

The authors are currently performing an investigator-
initiated study funded by 3M to assess the clinical
utility of the 3200 stethoscope in conjunction with Zargis Cardioscan software.

Editors’ note

See also the previous editorial by Alam et al. in the January/February issue earlier this year (Br J Cardiol 2010;17:8–10).

Key messages

Cardiac auscultation is an essential part of the clinical examination

Cardiac auscultation skills have declined, possibly due to the introduction of newer technologies such as echocardiography

Technological innovations, such as electronic stethoscopes, multimedia applications and patient simulators, are now available to assist in the teaching of cardiac auscultation

A combined approach, which maintains clinical exposure, utilising clinical experience, but incorporates technological innovation to reinforce learning, may be the best way forward

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