cardiac auscultation 101 a basic science approach to diagnosing heart murmurs

Cardiac auscultation 101: A basic science approach to diagnosing heart murmurs

Christopher Hanifin, PA-C

Cardiac auscultation 101: A basic science

approach to diagnosing heart murmurs

HTML Source: Cardiac auscultation 101: A basic science approach to diagnosing heart murmurs


April 06 2010

KEY POINTS

• In order to make sense of the sounds heard during cardiac auscultation, a thorough

understanding of which valves should be open and which should be closed during systole

(cardiac contraction) and diastole (cardiac relaxation) is needed.

• Blood, like all fluids, flows from an area of high pressure to an area of low pressure. Pressure

gradients determine the direction and velocity of blood flow as well as when the valves open and

close.

• Fluid is a fairly efficient carrier of sound. If pathology generates turbulent blood flow within

the heart, the associated murmur usually radiates to a fairly predictable location.

• Auscultation is carried out at five to six discrete areas on the precordium. Each of these areas is

associated with a particular valve; however, not all pathology associated with a valve can be

heard best at its named anatomic location.

Cardiac auscultation can be frustrating to learn. Many physical examination textbooks present

cardiac auscultation in a simplistic fashion: Simply memorize a table, auscultate the precordium

in five spots with the stethoscope bell and diaphragm, and arrive at a diagnosis. Clinicians who

seek to further refine their skills are confronted with a variety of audio programs that present a

dizzying array of cardiac recordings. The average clinician quickly discovers that it will take

years of practice to become skilled in cardiac auscultation.

http://www.jaapa.com/cardiac-auscultation-101-a-basic-science-approach-to-diagnosing-heart-murmurs/article/167102/

http://www.jaapa.com/christopher-hanifin-pa-c/author/708/




Given the easy availability of echocardiography and other technologic interventions in many

locations, auscultation may not appear to be a cost-effective skill to learn. Some authors believe

that a marked deterioration in cardiac physical examination skills is occurring.1 Repeated studies

have demonstrated what is being referred to as a "disturbingly low identification rate" for

common murmurs.2-4

As complex and subtle as many cardiac auscultatory findings are, a return to the fundamental

principles learned in basic science classes will assist the clinician with arriving at a diagnosis in

many cases. Instead of encouraging memorization, this article discusses how knowledge of the

anatomy and physiology of the heart assists with making an accurate diagnosis.

CARDIAC ANATOMY AND

PHYSIOLOGY

Effective evaluation of a heart murmur is very

difficult to accomplish without a thorough

understanding of the cardiac cycle and its associated

circulatory pattern. In order to make sense of the

sounds heard during cardiac auscultation, a thorough

understanding of which valves should be open and

which should be closed during systole (cardiac

contraction) and diastole (cardiac relaxation) is

needed. The heart has four major valves that promote

a unidirectional flow of blood through the circulatory

system. The valves are located in a band of

fibrocartilaginous tissue in the center of the heart5

(Figure 1). A healthy valve is quite pliable; it opens

with little resistance and closes, or coapts, tightly to

prevent retrograde blood flow.

The atrioventricular (AV) valves—mitral valve and

tricuspid valve —separate the atria from the ventricles.

The mitral valve is located between the left atrium and

left ventricle; the tricuspid valve is located between

the right atrium and right ventricle. These valves

prevent retrograde blood flow into the atria during



ventricular systole. Although simple in appearance, AV-valve function is complex. AV valves

rely on anchoring apparatus (the chordae tendineae and papillary muscles) and on proper

ventricular wall motion during systole to coapt tightly. Anything that hampers heart wall motion,

such as ischemia, can contribute to valve dysfunction.

The semilunar valves—aortic valve and pulmonic valve —separate the ventricles from the

major vessels that leave the heart—the aorta and the pulmonary artery. The architecture of the

semilunar valves is somewhat simpler than that of the AV valves. The semilunar valves have

three leaflets with deep cusps. The depth of the cusps forms a large surface area for coaptation.

The semilunar valves prevent retrograde blood flow into the ventricles during diastole.

Systole Intraventricular pressure rapidly increases as systole begins. The AV valves close,

normally synchronously, producing the heart sound called S1. The mitral component of S1 is

usually louder than the tricuspid component because pressures in the left side of the heart are

greater. As the pressure in the ventricles becomes greater than the pressure in the great vessels,

the aortic valve and pulmonic valve open, allowing forward blood flow. This flow is usually

silent.

Diastole As systole concludes and intraventricular pressure drops, higher pressure in the

systemic and pulmonic circulation causes the semilunar valves to close, producing the heart

sound called S2. Pressure in the systemic circuit (left side of the heart) is much higher than

pressure in the pulmonic circuit; therefore, the aortic component of S2 is usually significantly

louder than the pulmonic component. Although the semilunar valves also typically close

synchronously, differences in pressure in the pulmonary circuit related to breathing often cause

the sounds to split during inspiration.

The aortic and pulmonic valves remain closed during diastole. Blood flows at a low velocity

through the pliable, widely-open mitral and tricuspid valves, filling the ventricles in preparation

for the next systole. Thus, in the absence of pathology, diastole is silent.

Distinguishing between right- and left-sided murmurs is sometimes challenging, but knowledge

of anatomy and physiology can often help. The right side of the heart distributes blood into the

pulmonary circuit; therefore, it is very susceptible to pressure changes that occur in the

pulmonary vasculature during ventilation. Right-sided heart murmurs will therefore often change

in intensity during breathing, increasing with inspiration.

PHYSICS OF BLOOD FLOW

Blood, like all fluids, flows from an area of high pressure to an area of low pressure. Pressure

gradients determine the direction and velocity of blood flow as well as valve opening and

closure. For example, the aortic valve opens when intraventricular pressure rises above aortic

pressure. Blood will also flow down a pressure gradient across any abnormal pathway present in

the heart. For example, a ventricular septal defect (VSD) usually results in blood flow from the

left ventricle into the right ventricle because pressure on the left side of the heart is usually much

higher than pressure on the right side.



Smooth, laminar fluid flow is generally silent. As increasing turbulence develops in moving

fluid, a proportionate level of sound is produced. Turbulence that becomes severe produces a

palpable vibration called a thrill.

Finally, fluid is a fairly efficient carrier of sound. If pathology generates turbulent blood flow

within the heart, the associated murmur usually radiates to a fairly predictable location. For

example, pathology in the aortic valve that causes a murmur is generally heard not only over the

valve but also at the aortic area and at the cardiac apex.

MURMUR ORIGINS

Murmurs are apparent when blood flow becomes turbulent. The main causes of turbulent blood

flow within the heart are diseased heart valves or an abnormal blood-flow pathway within the

heart or great vessels. Valve pathology may appear complex, but fundamentally, a valve is

nothing more than a door. In general, two things

can go wrong with a door: either it does not open

properly or it does not close properly (Figure 2).

Diseased heart valves A stenotic valve is one that

fails to open easily. Valve tissue is normally quite

pliable and presents little resistance to forward

blood flow. As a valve becomes increasingly

stenotic, the column of blood pushed through its

orifice will become increasingly forceful and

turbulent. A stenotic valve often demonstrates

some combination of leaflet thickening, leaflet

fusion, and calcification. Stenosis may develop for

a variety of reasons. For many years, the most

common reason was rheumatic heart disease. Now

that the incidence of rheumatic fever has decreased

in the United States and the average life span has

increased, connective tissue disorders and simple

wear and tear are more important etiologic factors.

A regurgitant (or incompetent) valve is one that fails to close properly. When the valve leaflets

fail to properly coapt, retrograde blood flow occurs across the valve. In addition to the factors

that cause stenosis, many other factors may lead to valvular incompetence. Infectious

endocarditis may lead to rapid destruction of a valve; a mechanical problem, such as rupture of a

chorda tendineae, may result in regurgitation; and wall-motion abnormalities secondary to

cardiac ischemia may prevent proper valvular coaptation. In some cases, a damaged valve



demonstrates a degree of both stenosis and regurgitation: It cannot open fully, presenting an

obstacle to forward flow; it also cannot close properly, leading to regurgitation.

Abnormal blood-flow pathway The other chief cause of cardiac murmur is an abnormal blood-

flow pattern resulting from an anatomic abnormality. Most of these abnormalities are congenital

and represent either an error of development (eg, VSD) or a remnant of fetal circulation (eg,

patent ductus arteriosus). Although less common, an abnormal communication between heart

chambers may be acquired. For example, an infarction involving the septum may result in a

rupture. This defect would permit blood to flow from the high-pressure left ventricle to the low-

pressure right ventricle during systole.

The intensity of a murmur can provide some clues regarding the nature of the defect. Pitch and

intensity are related to the velocity of blood flow that produces the murmur. A higher pressure

gradient between two compartments produces a higher velocity of blood flow between those

compartments. As an example, one could expect a fairly high-velocity jet of blood to flow from

the left ventricle to the right ventricle during systole if a VSD is present.

The size of the orifice that blood must pass through also plays a role in determining the nature of

the associated murmur. A mildly stenotic valve or large septal defect allows blood to flow at a

relatively low velocity and produces a low-pitched rumbling murmur. A tight stenotic valve or

small defect results in a higher flow velocity, thereby producing a higher-pitched murmur. As an

analogy, water pouring freely out of a garden hose does so relatively quietly. Pressing a thumb

over the end of the hose introduces stenosis; as the orifice becomes smaller, the velocity of water

leaving the hose increases as does the pitch and

intensity of the sound it produces.

CARDIAC AUSCULTATION

Heart murmurs are often subtle. Using a high-

quality stethoscope in a quiet environment

maximizes the chances of identifying a murmur.

Clinicians often take a shortcut during cardiac

auscultation by failing to auscultate for low-

frequency murmurs with the bell of the stethoscope.

Omitting this step is hazardous, as the clinician may

overlook a subtle murmur associated with early

pathology or right-sided heart lesions. Auscultation

is carried out at five to six discrete areas on the

precordium (Figure 3). Each of these areas is

associated with a particular valve; however, not all

pathology associated with a valve can be heard best

at its named anatomic location. For example, some

pathology associated with the aortic valve can be

heard better at the apex than at the aortic area.



The first step is to distinguish S1 and S2—that is, to determine when systole and diastole are

occurring. Although this may seem obvious, the task often proves more challenging than one

would expect, particularly if a patient's condition causes tachycardia. With slower heart rates,

diastole is noticeably longer than systole. An easy way to distinguish systole from diastole in a

tachycardic patient is to auscultate the heart and simultaneously palpate the carotid pulse, which

coincides with systole.

Many clinicians begin by listening to the aortic area. This area does not overlie the aortic valve.

Instead, it is at the second right intercostal space, which overlies a location where sounds

related to aortic pathology are likely to be projected. As an example, aortic stenosis typically

produces a high-velocity jet of blood directed toward the aortic area. In similar fashion, the

second left intercostal space is referred to as the pulmonic area. It overlies the area where

pathologic sounds from the pulmonic valve are usually projected.

The third left intercostal space is referred to as Erb's point. At this location, the stethoscope is

in close proximity to both semilunar valves. This is a useful location to auscultate when aortic or

pulmonic valve pathology is suspected. If subtle pathology is suspected, having the patient

exhale and lean forward may bring the heart and great vessels slightly closer to the chest wall,

enhancing auscultation.

The fourth left intercostal space at the left sternal border is referred to as the tricuspid area.

This space overlies the right ventricle and provides a good window for auscultating the right

ventricle for tricuspid or pulmonic pathology.

The cardiac apex, referred to as the mitral area, is at the fifth left intercostal space. As the bulk

of the left ventricle lies posterior to the right ventricle, the apex provides the best window for

auscultating the left ventricle. Rolling a patient onto the left side may sometimes bring the left

ventricle slightly closer to the chest wall, improving auscultation.

USING LOCATION TO DIAGNOSE VALVE

PATHOLOGY

Aortic area A significant murmur heard at the aortic area usually indicates pathology of the

aortic valve or left ventricular outflow tract. In aortic stenosis and hypertrophic cardiomyopathy

(HCM), blood encounters an obstruction while exiting the left ventricle. This obstruction

produces a fluid jet that introduces turbulence into the aorta during systole. In aortic

regurgitation, a diastolic murmur may be heard over the aortic area; one would also expect to

hear an associated diastolic murmur at the apex because aortic regurgitation results in retrograde

blood flow into the left ventricle.

Pulmonic area Murmurs from pulmonary valve pathology tend to be subtle because the pressure

circuit on the right side of the heart is lower. The proximity of the aortic valve also tends to

drown out sounds. The machinery murmur associated with patent ductus arteriosus is also heard

best at the pulmonic area.



If pulmonic valve pathology is suspected, a few steps may help clarify the diagnosis. Pulmonic

murmurs tend to be audible over the right ventricle along the left sternal border, whereas aortic

murmurs are more distinct at the apex, where left ventricle sounds are more distinct. In addition,

the pulmonic valve is subjected to cyclical changes in pressure caused by pressure changes in the

pulmonary vascular tree. If the intensity of the murmur changes in relation to breathing,

pulmonary valve pathology is likely.

Left sternal border At the third left intercostal space, the stethoscope is particularly close to the

aortic and pulmonic valves. This location is therefore useful to hear abnormalities in S2 and

assess aortic and pulmonic valve function. As previously noted, the heart may be brought slightly

closer to the chest wall, thereby accentuating a murmur, if the patient leans forward and exhales

prior to auscultation. The diastolic murmur of aortic regurgitation may be heard best here and

should radiate toward the apex.

The fourth and fifth intercostal spaces overlie the right ventricle and provide insight into

tricuspid valve function. A systolic murmur at this location suggests either pulmonic stenosis or

tricuspid regurgitation. Pulmonic stenosis generates a jet of fluid that projects sounds toward the

pulmonic area during systole. Tricuspid regurgitation, although subtle, usually projects sound

toward the right sternal border. Pressure is usually also transmitted back into the superior vena

cava, which leads to neck vein distention.

A diastolic murmur at the left sternal border suggests tricuspid stenosis or pulmonary

regurgitation. Again, these murmurs may be difficult to discern because pressure on the right

side is lower. Both of these conditions may lead to neck vein distention.

Apex (during systole) Most of the left ventricle lies tucked behind the right ventricle, which can

make auscultation challenging. The best acoustic access to the left ventricle is at the apex. In

cases in which the findings may be subtle, rolling the patient onto his or her left side may help

bring the left ventricle closer to the stethoscope.

Blood has three potential exits from the left ventricle. In a normal heart, blood will exit the

ventricle during systole via the aortic valve. If mitral valve pathology is present, blood may flow

in a retrograde direction into the left atrium. If an abnormal connection between the ventricles

exists, blood will usually flow into the lower-pressure right ventricle. Therefore, a systolic

murmur heard best at the apex suggests three diagnoses: aortic outflow obstruction, mitral

regurgitation, or VSD.

To differentiate between the three diagnoses, consider the direction of blood flow associated with

each condition. Aortic obstruction projects a high-pressure jet of blood toward the aortic area

during systole. Depending on the degree of turbulence, an associated thrill may be palpable at the

aortic area or the murmur may radiate into the carotid arteries. Aortic obstruction may occur at

the level of the valve or below the valve, as in HCM.

Conversely, mitral regurgitation projects a jet of blood in a retrograde fashion into the left

atrium. The sound tends to be projected toward the left axilla. In the presence of a VSD, blood



typically flows from the left ventricle to the right ventricle, projecting a murmur along the left

sternal border. The intensity of the murmur depends on the size of the defect and the degree of

pressure difference between the ventricles. If pulmonary hypertension is present, the murmur

may be subtle because the pressure gradient between the ventricles is small.

Apex (during diastole) The heart is normally quiet during diastole. The aortic valve is closed

and blood flows into the left ventricle through the mitral valve. An apical diastolic murmur thus

suggests two diagnoses: mitral stenosis or aortic regurgitation. Normally, the mitral valve is quite

pliable and presents little resistance to blood from the lungs traveling to the left ventricle. If the

mitral valve becomes stenotic, the atrium must fill with a certain volume of blood before the

valve is forced open. This produces a characteristic "opening snap" and murmur heard at the

apex during diastole.

In aortic regurgitation, the aortic valve leaflets fail to coapt properly and allow retrograde

blood flow into the left ventricle. An Austin Flint murmur—the characteristic murmur of aortic

regurgitation named for the American physician Austin Flint, MD—can be heard at the aortic

area, at Erb's point, and at the apex. Having the patient sit upright, lean forward, and exhale

brings the aortic valve closer to the chest wall and may help accentuate a subtle murmur.

PHYSIOLOGIC MANEUVERS AND MURMURS

In addition to positioning the patient to bring the heart closer to the chest wall, a clinician can

also take advantage of maneuvers that alter a patient's hemodynamics transiently. Instead of

attempting to memorize the effect of a maneuver on a particular murmur, a clinician is better

served by understanding how a particular maneuver alters blood return to the heart ( preload ) or

systemic pressure (afterload ).

One frequently used maneuver is the squat. Squatting causes the large pool of blood in the legs

to return to the heart, transiently increasing preload. As this excess blood transits the heart, the

volume of blood that must traverse a stenotic valve increases. In the case of pulmonic or aortic

valve stenosis, the increased volume of blood generally increases the murmur. In the case of

HCM, the increased volume often distends the left ventricle and may paradoxically diminish the

murmur. If a patient is unable to stand, a Valsalva maneuver can be used to increase intrathoracic

pressure and decrease preload. Releasing a Valsalva maneuver transiently increases preload,

which produces the same effect as squatting.

Isometric exercise of the upper extremities (most commonly hand grasping) raises afterload and

is particularly useful for diagnosing aortic valve pathology. In the case of aortic stenosis and

HCM, increasing pressure in the systemic circulation reduces the pressure gradient across the

valve and should diminish a murmur. The opposite is the case in aortic regurgitation, where

increased systemic pressure promotes increased regurgitation through the incompetent valve.



CONCLUSION

The stethoscope has long been a symbol of medical practice, but competence with a stethoscope

is a hard-earned skill. Time devoted to becoming proficient at auscultation is a worthwhile

investment, even if it is used only as a means to screen for conditions that can be better evaluated

with another technique.1 Although some patients will present with complicated, multivalvular

pathology that cannot be assessed with auscultation alone, keeping the basic facts in mind will

greatly assist with diagnosing many murmurs. JAAPA

Christopher Hanifin, PA-C is on the faculty of the Seton Hall University Physician Assistant

Program, South Orange, New Jersey, and works in the Department of Emergency Medicine,

Morristown Memorial Hospital, Morristown, New Jersey. The author has indicated no

relationships to disclose relating to the content of this article.

REFERENCES

1. Conn RD, O'Keefe JH. Cardiac physical diagnosis in the digital age: an important but in-

creasingly neglected skill (from stethoscopes to microchips). Am J Cardiol. 2009;104(4):590-

595.

2. Vukanovic-Criley JM, Criley S, Warde CM, et al. Competency in cardiac examination skills

in medical students, trainees, physicians, and faculty: a multicenter study. Arch Intern Med.

2006;166(6):610-616.

3. Mangione S, Nieman LZ. Cardiac auscultatory skills of internal medicine and family practice

trainees: a comparison of diagnostic proficiency. JAMA. 1997;278(9):717-722.

4. Mangione S. Cardiac auscultatory skills of physicians-in-training: a comparison of three

English-speaking countries. Am J Med. 2001;110(3):210-216.

5. Misfeld M, Sievers HH. Heart valve macro- and microstructure. Philos Trans R Soc Lond B

Biol Sci. 2007;362(1484):1421-1436.


http://www.jaapa.com/christopher-hanifin-pa-c/author/708/



From this Editor, Dr. Cray, additional resources:

Heart Songs 3

Heart Songs 3 provides you with high-quality heart sounds that you can look at

and listen to at your convenience to improve your cardiac auscultation skills!

Master heart sounds - basic, intermediate, and complex - with a program designed

specifically to help you learn in the way that your brain processes auditory

information. Heart Songs 3 is based on psychoacoustic research that's shown

intensive repetition (400 to 600 times) to be key, producing a significant

improvement in cardiac auscultation in a relatively short time. Once each new

sound is mastered, it will be reinforced every time you hear it in a patient.

Modeled after its successful predecessors, Heart Songs 3 includes all the murmurs from the

previous version plus images of phonocardiograms, CT scans and even videos of color Doppler

echocardiograms! These visual enhancements will facilitate your understanding and mastery of

many heart murmurs.

Editor: Michael J. Barrett, MD, FACC

Target Audience: The target audience includes any healthcare professional interested in

improving his/her cardiac auscultation skills.

Format: This program is available online and features three key sections:

Heart Songs in MPEG-4 files for use on devices that support this video format

Heart Songs in MP3 files (audio only) for use on any MP3 player that does not support

video.

Interactive online quizzes.

Sample Heart Songs (click on the links to open)

1. Introduction

2. Mitral Regurgitation

3. Aortic Stenosis

4. Innocent Systolic Murmur

5. Aortic Regurgitation

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/Heart-Songs-3.aspx

http://www.cardiosource.org/Shared-Content/Experts/B/Barrett-Michael.aspx

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/~/media/Files/HeartSongs3/samples/01%20Introduction.ashx

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/~/media/Files/HeartSongs3/samples/02%20Mitral%20Regurgitation_sample.ashx

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/~/media/Files/HeartSongs3/samples/03%20Aortic%20Stenosis_sample.ashx

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/~/media/Files/HeartSongs3/samples/04%20Innocent%20Systolic%20Murmur_sample.ashx

http://www.cardiosource.org/Certified-Education/eLearning-and-Products/~/media/Files/HeartSongs3/samples/05%20Aortic%20Regurgitation_sample.ashx









Introduction: Examination for Heart Sounds & Murmurs

This module contains descriptions of techniques for the cardiac physical examination, focusing

on heart sounds and murmurs. Other aspects of the cardiovascular examination are discussed in

the modules on neck veins and pulmonary examination. Primary goals of this module are to

enhance comfort in detecting and identifying heart sounds and to learn how to further evaluate

murmurs…ENTER THE WEBSITE

Continuing Medical Education

Heart Sounds Podcast Series

Produced by:

Robert J. Hall Heart Sounds Laboratory

Featuring:

James M. Wilson, MD

Director, Cardiology Education

Texas Heart Institute at St. Luke’s Episcopal Hospital

Updated March 22, 2011

By: Marc Imhotep Cray, M.D.

19 p.

IVMS ICM-Heart Murmurs

12 p.

IVMS Basic Medical

Science of Valvular Heart Disease

http://depts.washington.edu/physdx/heart/index.html

http://texasheart.org/Education/CME/explore/events/eventdetail_6456.cfm

http://texasheart.org/AboutUs/ProfStaff/adult_4.cfm#wilson

http://www.scribd.com/Marc%20Imhotep%20Cray,%20MD

http://www.scribd.com/doc/56178483/IVMS-ICM-Heart-Murmurs







http://www.scribd.com/doc/32530579/IVMS-Basic-Medical-Science-of-Valvular-Heart-Disease




































cardiac auscultation 101 a basic science approach to diagnosing heart murmurs

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