Anatomy

The heart has four chambers: the right atrium, right ventricle, left atrium, and left ventricle. Unidirectional valves, the heart valves, separate the chambers on each side of the heart and the exit from each ventricle. Therefore, the heart has four valves: two atrioventricular (AV) valves and two semilunar (SL) valves guarding the exit from each ventricle. There are no valves at the entrance of either atria. Therefore, abnormally high pressure in the right side of the heart can be seen as distension of the neck veins and abdomen, and abnormally high pressure on the left side gives a person symptoms of pulmonary congestion. 

The AV valve on the right side is the tricuspid valve, and the left AV valve is the mitral valve. The thin leaflets of these valves are anchored by collagenous fibers, the chordae thendineae, to papillary muscles embedded in the ventricle floor. During the filling phase, or diastole, blood flows from the atrium to the ventricle, and the valve opens. During the pumping phase, or systole, the AV valves close to prevent backflow or regurgitation of blood back into the atria. The papillary muscles contract during the systole, so the valve leaflets meet and unite to form a perfect seal without turning themselves inside out. 

Between the ventricles and the arteries are the semilunar valves. Each valve has three cusps that look like half-moons. The SL valves are the pulmonic valve on the right side and the aortic valve on the left side of the heart. These valves open during the systole to allow blood to flow out of the ventricles and close during diastole to fill the ventricles. 

Heart Sounds

Heart sounds are created by blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations of these structures from the blood flow create audible sounds — the more turbulent the blood flow, the more vibrations are produced. The variables determining blood flow turbulence include fluid viscosity, density, velocity, and the column diameter through which the fluid travels. Auscultation of the heart sounds with a stethoscope is a cornerstone of physical medical exams and a valuable first-line tool to evaluate a patient. Some sounds are characteristic of significant pathological lesions with major pathophysiological consequences, first present on auscultation. These lesions can be heard in systole, diastole, or continuously through the cardiac cycle.

Auscultation

It takes much practice to perform a smooth and complete cardiovascular exam. Auscultation is a key component and perhaps the hardest to master. To become a proficient provider, one must practice hearing normal and pathological sounds. Consider that at least two, and perhaps three or four, sounds may be happening in less than 1 second. Thus, it is impossible to process everything at once. Concentrate and listen selectively to one sound at a time. 

A traditional stethoscope has two sides

• Bell: best for low-pitched sounds
• Diaphragm: best for high-pitched sounds

Where to Listen

A cardiovascular exam should include auscultation in four areas, each covering a specific valve. These areas do not necessarily correspond with the valves' anatomical location but are where the valve action is best heard.

• Aortic: Best heard in the second intercostal space at the right sternal edge
• Pulmonary: Best heard in the second intercostal space at the left sternal edge
• Mitral: Best heard in the fifth intercostal space on the left mid-clavicular line
• Tricuspid: Best heard at the fifth intercostal space at the left sternal edge

Begin by auscultating each area with the stethoscope's diaphragm and then repeat with the bell of the stethoscope. Alternatively, alternate between the two at each location. The carotid pulse can be palpated on one side whilst listening to the heart to aid with the identification of S1 (it occurs at the same time as the carotid pulsation).

Additional areas may be focused on depending on the underlying suspected pathology. For example, the murmur of aortic stenosis may be heard to radiate to the carotids, whilst mitral regurgitation may radiate to the axilla.

Patient Position

During most of the examination, the patient should be positioned on a couch with the head of the bed angled at 45 degrees.

After auscultating the four areas described above, carry out the following position changes (in those who can tolerate them) to accentuate murmurs:

• Aortic regurgitation: Ask the patient to sit up and lean forward whilst listening at the left sternal edge
• Mitral stenosis: Ask the patient to lie on their left side and listen at the apex with the bell of the stethoscope

Dynamic Maneuvers

Most murmurs will increase or decrease in volume when the patient performs certain maneuvers. This dynamic quality of murmurs is used as a clinical tool during the patient's physical exam to diagnose a specific murmur. Dynamic maneuvers can help to identify murmurs

• Handgrip: Increases afterload. Handgripping enhances the strength of murmurs associated with aortic regurgitation, mitral regurgitation, and ventricular septal defects. It reduces the intensity of murmurs resulting from hypertrophic obstructive cardiomyopathy and mitral valve prolapse.
• Squatting: Increases preload and intensifies aortic stenosis, mitral stenosis, aortic regurgitation, and mitral regurgitation. It also reduces the strength of murmurs caused by hypertrophic obstructive cardiomyopathy and mitral valve prolapse.
• Valsalva: Decreases preload and increases the strength of murmurs caused by hypertrophic obstructive cardiomyopathy (HOCM) and mitral valve prolapse. It also reduces the intensity of aortic stenosis, mitral stenosis, aortic regurgitation, mitral regurgitation, and ventricular septal defects.
• Standing abruptly: Decreases preload and has the same effects as Valsalva. Sudden standing increases the intensity of murmurs in hypertrophic obstructive cardiomyopathy and mitral valve prolapse. It decreases the strength of aortic stenosis, mitral stenosis, aortic regurgitation, mitral regurgitation, and ventricular septal defects
• Respiration: Right-sided murmurs are louder on inspiration; left-sided murmurs are louder on expiration. This can be remembered with R-I-L-E (right on inspiration, left on expiration)

Overview Video

This video gives a concise overview of common heart sounds with audio.

Four Primary Heart Sounds

Healthy adults will typically have two heart sounds: S1 and S2.

The sounds are often described as 'lubb (S1) dub (S2)' and are caused by the closure of the atrioventricular and semilunar valves during the cardiac cycle.

S1

The first heart sound, S1, is heard when the AV valves (the mitral and tricuspid valves) close. The beginning of ventricular systole prompts their closure due to increased ventricular pressure.

On auscultation, S1 is heard best at the apex of the heart.

S2

The second heart sound, S2, is heard when the semilunar valves (the pulmonary and aortic valves) close. During ventricular diastole, the pressure differential between the great vessels (pulmonic artery and aorta) and the ventricles forces the closure of these valves.

Typically, the pulmonary valve closes just after the aortic valve as right ventricular ejection lasts slightly longer. This is accentuated during inspiration, where increased venous return (intra-thoracic pressure drops during inspiration, drawing blood in) results in the prolongation of right ventricular ejection. S2 may be heard as 'split' into A2 and P2 components [aortic closure sound (A₂) and the pulmonic closure sound (P₂)] - a finding referred to as physiological splitting.

Abnormal splitting may be indicative of disease

• Single S2/Reversed split: Heard in aortic stenosis
• Fixed Splitting: Heard in atrial septal defects
• Exaggerated Splitting: Heard in pulmonary stenosis, ventricular septal defect, and mitral regurgitation

S3

Typically, diastole is a silent event. However, in some conditions, ventricular filling creates vibrations that can be heard over the chest. These vibrations are S3. The S3 heart sound occurs when the ventricles resist filling during the early rapid filling phase (protodiastole). This happens immediately after S2, when the AV valves open and atrial blood pours into the ventricles. The sound is dull, soft, and low-pitched, like "distant thunder." It is best heard with the bell held lightly, at the apex, and with the person in the left lateral position.

S3 may be heard in healthy children and young adults and is considered normal (physiologic) for these individuals. Occasionally, it may be heard after age 40, especially in women. The normal S3 usually disappears when the person sits up.

However, in older patients, S3 is usually abnormal (pathologic). A pathologic S3 is also known as a ventricular gallop or an S3 gallop. It persists when sitting up and indicates decreased compliance of the ventricles, as in heart failure. A left-sided S3 is heard at the apex in the left lateral position, and a right-sided S3 is heard at the left lower sternal border with the person supine and is louder in inspiration. 

The S3 can also be heard with volume overload conditions (eg, mitral, aortic, or tricuspid regurgitation) and with high cardiac output states without heart disease (eg, hyperthyroidism, anemia, and pregnancy).

S4

A fourth heart sound, S4, may be heard in otherwise healthy older patients. It is a ventricular filling sound that occurs when the atria contract late in diastole. S4 is heard immediately before S1. It is very soft and very low-pitched, and you must listen for it. It is best heard at the apex, with the person in the left lateral position. 

An S4 may occur in adults older than 40 or 50 with no evidence of cardiovascular disease, especially after exercise, and would be considered normal (physiologic). 

A pathological S4 is also known as an atrial gallop or S4 gallop. This sound may indicate a non-compliant ventricle due to conditions such as coronary artery disease or cardiomyopathy and can arise with systolic overload (afterload), including ventricular outflow obstruction (eg, aortic stenosis) and systemic hypertension. A left-sided S4 is associated with these conditions and is best heard at the apex when the patient is in the left lateral position. 

A right-sided S4 is less common and typically occurs in cases of pulmonary stenosis or hypertension. It is best heard at the left lower sternal border and may increase during inspiration.

Additional Sounds

• Ejection Click: Typically, the SL valves open silently, but in the presence of stenosis (eg, aortic or pulmonary stenoses), their opening makes a sound. This ejection click is a high-pitched sound heard at the moment of maximal (although severely diminished due to the fibrotic nature of the diseased valves) opening of the aortic or pulmonary valves. They occur early in systole at the start of ejection. Aortic and pulmonary clicks are most prominent along the upper right and left sternal border, respectively. They are heard just after the first heart sound and are best heard with the stethoscope's diaphragm. These clicks can be very difficult for the untrained practitioner to hear. 
• Midsystolic Click: Although the midsystolic click is systolic, it is not an ejection click. This click-sound is associated with mitral valve prolapse, in which the mitral valve leaflets not only close with contraction but balloon back up into the left atrium. During ballooning, the sudden tensing of the valve leaflets and the chordae tendinae creates the click (physically, when you suddenly tension a string, it vibrates and makes a sound). The sound occurs in the mid- to late systole and is short and high-pitched, with a click quality. It is best heard with the diaphragm, at the apex or left lower sternal border. The click and possible following murmur move with postural changes.
• Opening Snap: Typically, the opening of the mitral valve is silent. In mitral stenosis, increasingly higher atrial pressure is required to open the valve. The deformed valve opens with a noise: the opening snap. It is sharp and high-pitched, with a snapping quality. The snap is heard after S2 and is best heard with the diaphragm at the sternal border's third or fourth left interspace. 

Murmurs

Blood circulating through normal heart chambers (ie, atria and ventricles) and valves (ie, tricuspid, pulmonary, mitral, and aortic) creates no noise. However, certain conditions can alter blood flow or mechanical function. Typically, these changes include low blood viscosity due to anemia, septal defects, failure of the ductus arteriosus to close in newborns, excessive hydrostatic pressure on cardiac valves resulting in valve failure, hypertrophic obstructive cardiomyopathy, and valvular-specific pathologies. Regardless of the underlying etiology, all involve the creation of disturbed blood flow, which produces a murmur.

Auscultation

A murmur is a soft, blowing, swooshing sound that can be heard on the chest wall. 

Murmurs can represent valvular pathology (abnormal) or be physiological (normal). There are several things to consider to help this process

• Its timing in the cardiac cycle
  • Systolic murmurs occur between the first heart sound (S1) and the second heart sound (S2)
  • Diastolic murmurs occur between S2 and S1.
• Its character and grade (see Levine scale below)
  • Listen for additional aspects of the murmur's sounds
  • Heart murmurs may have qualities that can be noted as musical, harsh, blowing, booming, sharp, or dull
  • Other qualities
    • Crescendo: a murmur that increases in intensity
    • Decrescendo: a murmur that decreases in intensity
    • Crescendo-decrescendo: a murmur that initially increases in intensity, peaks, and then decreases in intensity
    • Plateau: static intensity
• Location of murmur; where is it the loudest
  
  • Auscultation of the heart is typically performed over five heart auscultation areas on the anterior chest wall (see image above)
    • Aortic valve: second intercostal space at the right sternal border.
    • Pulmonary valve: second intercostal space at the left sternal border.
    • Tricuspid valve: fourth intercostal space at the left sternal border.
    • Mitral valve: fifth intercostal space at the left midclavicular line.
    • Radiation:  murmurs may radiate, allowing auscultation at remote locations
• Pitch - is it best heard with the bell or diaphragm
  • Evaluation of the murmur's pitch should be made by classifying the pitch (frequency) as low, medium, or high
  • The stethoscope's bell can be helpful with low-pitched sounds, while the diaphragm is used for medium or high-pitched sounds
• Change with position or dynamic manoeuvres
  • Respiration or patient position can influence murmur intensity as well as heart sound splitting
  • Generally speaking, murmurs increasing with expiration originate with left side (aortic or mitral) valves, while murmurs increasing in intensity with inspiration originate with tricuspid or pulmonary valves
• Radiation
  • The murmur may be transmitted downstream in the direction of blood flow and may be heard in another place (eg, the carotids, the precordium, the back, or the axilla)

The Levine grading can be used to grade murmurs

• Grade I: Very quiet, heard by experts
• Grade II: Slight murmur, should be heard by most examiners
• Grade III: Moderate, easily heard, no palpable thrill
• Grade IV: Loud, palpable thrill
• Grade V: Very loud, palpable thrill
• Grade VI: Can be heard without a stethoscope

It is very rare for a diastolic murmur to be grade 5 or above; as such, they are typically graded 1-4.

Common Murmurs

Innocent Murmur

Normal blood flow in the heart sometimes produces innocent murmurs. Turbulence in blood flow creates vibrations in the heart's tissues that are transmitted to the chest wall. Benign, innocent murmurs are pretty common in children.

This type of murmur can also be associated with non-cardiac conditions in adults, such as pregnancy, hyperthyroidism, exercise, and anemia. When these conditions are effectively treated, the systolic murmur typically disappears.

Systolic Murmurs

Aortic Stenosis

Aortic stenosis is a common valvular pathology affecting 2-7% of people over the age of 65. It is characterized by an ejection systolic 'woosh. '

This murmur has a medium pitch and is coarse, with a crescendo-decrescendo character. It is loudest in the second right intercostal space and radiates widely to the side of the neck, down the left sternal border, or to the apex.

Pulmonary Stenosis

Pulmonary stenosis is often viewed as part of congenital syndromes but can also be acquired later in life. Similar to aortic stenosis, it causes an ejection systolic murmur. The murmur resembles aortic stenosis; however, it is best heard at the second left intercostal space and radiates to the left side of the neck.

Hypertrophic Obstructive Cardiomyopathy (HOCM)

HOCM refers to a group of inherited conditions that lead to myocardial hypertrophy. It may be detected incidentally, through family screening, due to symptoms, or it may present with sudden cardiac death (which is the most common cause of sudden cardiac death in young individuals). The ejection systolic murmur is caused by left ventricular outflow obstruction. The mid to late systolic murmur is secondary to systolic anterior motion, or ‘SAM,’ of the mitral valve, which often radiates to the axilla. The strong contraction of the left ventricle causes the anterior leaflet to be sucked into the ventricle, blocking the flow into the aorta and causing an aortic murmur. At the same time, turbulent flow from the left ventricle to the left atrium causes a second murmur. Since the two murmurs coincide, you hear a single murmur.

The HOCM murmur is a harsh, early-peaking, diamond-shaped systolic murmur that starts at the beginning of systole and ceases well before S2.

Mitral Regurgitation

A mitral regurgitation murmur is a type of murmur that occurs throughout all of systole (pansystolic). It is often loud and blowing, with a mid-frequency pitch. It is best heard over the apex, and depending on the direction of the regurgitant jet, it may also radiate to the axilla. Both S1 and S2 are normal, and S3 is present. The murmur is generated by turbulent blood flow through the incompetent mitral valve leaflets into the left atrium. Both the left ventricle and the left atrium are enlarged.

Tricuspid Regurgitation

The incompetent tricuspid valve results in a murmur of tricuspid regurgitation. This condition may be primary (ie, associated with rheumatic heart disease, carcinoid syndrome, infective endocarditis, or Ebstein’s anomaly affecting the valve) or secondary (ie, caused by pulmonary hypertension and subsequent right ventricle dilation). In adults, most cases are secondary, also referred to as functional. The sound is soft, blowing, and pansystolic. It is best heard at the left lower sternal border during inspiration. S3/S4 are often present.

Ventricular Septal Defect

Ventricular septal defects (VSD) are common congenital heart defects that affect approximately 1 in 500 births. The size of the defect and the resulting shunt—an abnormal connection and blood flow between the pulmonary and systemic circulation—determine the clinical features. It may occur in isolation or alongside other cardiac malformations. It causes a pansystolic murmur due to blood shunting from left to right during systole. In more significant defects, changes to the right side of the heart due to elevated pressures can soften the murmur as pressures equalize. The reversal of the shunt, known as Eisenmenger’s syndrome, converts it into a cyanotic heart defect.

The murmur has a loud, harsh holosystolic sound. It is best heard at the left lower sternal border and may be accompanied by a thrill.

Diastolic Murmurs

Aortic Regurgitation

An aortic regurgitation murmur occurs due to an incompetent aortic valve, leading to regurgitant blood flow during diastole. This results in a murmur that is heard in early diastole. It is typically categorized as either acute (such as infective endocarditis, aortic dissection, or acute rheumatic fever) or chronic (such as rheumatic heart disease, a bicuspid aortic valve, connective tissue disorders, or arthritides) based on its presentation.

The murmur starts almost simultaneously with S2 (early diastole) and is soft, blowing, high-pitched, and decrescendo. It is best heard on expiration at the left sternal edge, third or fourth intercostal space, when the patient sits up and leans forward. The murmur may radiate down.

Pulmonary Regurgitation

Pulmonary regurgitation results from an incompetent pulmonary valve (due to infective endocarditis, carcinoid syndrome, iatrogenic, or pulmonary artery dilatation), causing regurgitant blood flow in diastole, which causes a murmur in early diastole. Mild pulmonary regurgitation is common and typically entirely asymptomatic (physiologic murmur). With more significant regurgitation, right ventricular dilatation, secondary tricuspid regurgitation, and heart failure may result.

The murmur can be challenging to differentiate from aortic regurgitation. It is best heard on expiration at the left sternal edge, third or fourth intercostal space, when the patient sits up and leans forward. The murmur may radiate down. 

Mitral Stenosis

Mitral stenosis is characterized by valvular obstruction caused by rheumatic heart disease (the most common cause), congenital mitral stenosis, mitral annular calcification, radiation-associated mitral stenosis, or carcinoid syndrome. It restricts flow from the left atrium to the left ventricle. Dyspnea, chest pain, or hemoptysis are often noted with mitral stenosis. 

This murmur typically produces a low-pitched mid-diastolic rumble murmur that does not radiate and is best heard with the bell of the stethoscope at the apex, with the person in the left lateral position. 

Tricuspid Stenosis

Tricuspid stenosis is characterized by valvular obstruction—due to rheumatic heart disease, carcinoid syndrome, or infective endocarditis—that restricts blood flow from the right atrium to the right ventricle. This condition is relatively rare, and when it occurs, it is usually associated with other valvular pathologies. Symptoms may include peripheral edema, ascites, dyspnea, or abdominal discomfort (secondary to hepatic congestion).

This murmur typically produces a low-pitched rumble in mid-diastole. It is best heard at the left mid- to lower sternal edge on inspiration using the bell of the stethoscope.