Auscultation Foci: Definition, Sound Mechanism, Intensity and Differential Diagnosis

There are four basic heart sounds called S1 to S4.

Auscultation of the heart is not synonymous with examination of the heart.

Examination of the heart begins with a general inspection for cyanosis , dyspnea , edema, or cachexia. This is followed by evaluation of jugular venous pressure (JVP), examination of the pulse and blood pressure.

This includes checking the fingers for splinter hemorrhages. Only then is the time to move to the chest and even then it is not yet the time to use the stethoscope.

Interpreting heart murmurs in children can be especially difficult.

Mechanism of sounds

Heart sounds (normal or pathological) are caused by turbulent blood flow. They include the sound of the shut-off valves. Laminar flow is silent. The turbulent flow makes a sound. An emotion is turbulence or a murmur so marked that it is palpable.

Inspection and palpation

Look at the chest and:

  • Notice if there is asymmetry.
  • Pectus excavatum can cause a discharge murmur in the absence of heart disease.
  • At the time of inspection, a thumping apex beat may be seen, as well as a parasternal lift of the right ventricular hypertrophy.

Look for the apex and note its character and position:

  • The normal position is at or near the fifth intercostal space at the midclavicular line.
  • If the vertex is not easily palpable, sit further laterally and lower. In cardiomegaly it can be quite markedly displaced.
  • It is less easy to feel obese or with a hyperinflated chest as in emphysema. If not palpable, test the right side for dextrocardia, but this is rare.
  • Place the palm of your hand to the left of the breastbone. Observe if there is a parasternal uprising or if any emotion can be felt.

Auscultation sites

The bell of the stethoscope is better for detecting low-frequency sounds, while the diaphragm is better for higher frequencies.

The bell is generally used to listen to the mitral valve and diaphragm at all other sites. Auscultation is generally performed with the patient sitting or reclining at approximately 45 °. Where variations are required, they will be described.

Mitral focus

  • At the apex beat, since the left ventricle is closer to the rib cage.

tricuspid focus

  • The lower right sternal margin is the point closest to the valve where auscultation is possible.

Pulmonary focus

  • The second left intercostal space near the sternum is where the infundibulum is closest to the rib cage.

Aortic focus

  • The second right intercostal space, near the sternum, is where the ascending aorta is closest to the rib cage.

The best place to hear the heart valves is not necessarily directly over the anatomical site.

Heart sounds

The intensity of heart sounds and murmurs is classified as follows on the Levine scale:

  • I – lower intensity: difficult to hear even by experts.
  • II – low intensity: however, generally audible to all listeners.
  • III – medium intensity: easy to hear even for inexperienced listeners, but without a palpable emotion.
  • IV – medium intensity: with a palpable emotion.
  • V – high intensity: with a palpable emotion. Audible even with the stethoscope placed on the chest, with the rim of the diaphragm.
  • VI – higher intensity: with a palpable emotion. Audible even with the stethoscope raised on the chest.

Listen to the sounds of the heart first. They are called S1 and S2 and are traditionally described as ‘lub’ and ‘dub’ respectively. The first sound (S1) is caused by the closure of the mitral and tricuspid valves and the two sounds tend to merge as one.

When considered separately, the closure of the mitral and tricuspid valves is termed M1 and T1 respectively. The second sound (S2) is caused by the closure of the aortic and pulmonary valves.

They are slightly separated with the aortic component, also called A2, slightly after pulmonary closure called P2.

  • The first sound can be divided if there is pacing that fires the right ventricle earlier than the left or if mitral valve closure is delayed by high left atrial pressure or atrial myxoma.
  • Sounds may be softer than normal when there is severe mitral regurgitation, calcification immobility, severe aortic regurgitation, or left bundle branch block.
  • A prolapsed mitral valve or significant mitral stenosis can cause a strong M1.
  • Normally A2 and P2 are so close that they are heard as a single sound, although they may split slightly into deep inspiration as P2 is delayed. Some people have a significant split when lying down, but it disappears when sitting down. This is a normal variation.
  • Beat-to-beat variation in S2 intensity occurs with complete or incomplete heart block if AV dissociation is present.
  • P2 is delayed and will accentuate the division into pulmonary hypertension, pulmonary stenosis, and right bundle branch block.
  • Ectopic beats and rhythm will delay A2 and cause “reverse splitting” of the sound.

Additional sounds

Differentiating the 3rd sounds, 4th sounds, opening apertures, and widely divided S1 or S2 can be daunting.

  • A third sound is produced in heart failure and produces a cadence like a galloping horse. Hence the term “gallop rhythm.” An innocent third sound can occur in children and young adults, but never older than 30 years.
  • A fourth sound occurs just before the first and is an abnormal sound of the AV valves opening as the atria contract. Therefore, it cannot occur in atrial fibrillation. It occurs with ventricular hypertrophy, coronary heart disease, dilated cardiomyopathy, hyperdynamic circulation, arrhythmia, and heart block.
  • The timing of an opening snap in mitral stenosis is similar. It is usually of rheumatic origin. Again, atrial systole is essential and therefore cannot occur in atrial fibrillation.
  • An atrial myxoma can “drop” during atrial systole and cause a late diastolic sound.


Take into account the timing of the murmurs. Establish if it is systolic or diastolic. Listen to the lub dub first and then get the time. Some murmurs can obscure the sounds heard.

Systolic murmurs may be innocent, but they rarely are unless the patient is a girl or is pregnant. Diastolic murmurs are always pathological.

Mitral murmurs

  • Mitral murmurs are best heard at the apex and radiate to the axilla.
  • Mitral sounds can be accentuated with the patient in the left lateral position.
  • So, to hear a mitral murmur, first listen to the apex, then listen around the mid-axillary line at the same level. Return the bell to the apex and, holding it there, ask the patient to lie on the left side.
  • Take into account the time of any murmur. Mitral regurgitation produces a pansystolic murmur of approximately uniform intensity throughout systole.
  • Mitral stenosis produces a diastolic murmur described as presystolic.
  • As soon as the murmur ends, the first sound is heard.
  • Mitral valve prolapse produces a mean systolic click.
  • The Austin Flint murmur can occur in aortic regurgitation. This is a soft, rumbling, low-pitched, late diastolic murmur best heard at the vertex.

It is believed to be due to functional mitral valve stenosis, as the back flow of blood from the aorta presses on the anterior leaflet of the mitral valve, slightly occluding flow from the atria.

The atrial kick just before systole accentuates this flow to produce the Austin Flint murmur.

Tricuspid murmurs

  • Tricuspid murmurs are rare. The timing is for mitral murmurs, but they are best heard at the lower right sternal border.
  • Tricuspid stenosis is very rare. Regurgitation can occur in right ventricular hypertrophy and dilated cardiomyopathy. It will produce a marked wave on the JVP.
  • Tricuspid regurgitation does not radiate to the armpit.

Pulmonary and aortic murmurs

The pulmonary and aortic valves are best heard in the 2nd intercostal space, on the left and right respectively. This can make differentiation quite difficult.

Sound from the aortic valve is often transmitted to the carotid and can be heard by placing a stethoscope over the bifurcation of the carotid.

  • Pulmonary stenosis will produce a flow murmur that becomes louder and softer (crescendo-decrescendo) during systole. Pulmonary ejection sounds, unlike aortic ones, tend to diminish or disappear on inspiration.
  • A similar sound occurs with aortic stenosis but is transmitted to the carotids.
  • Aortic sclerosis occurs in the elderly and produces a murmur similar to aortic stenosis, but it is poorly transmitted or not transmitted to the carotids. It is transmitted to the apex and mid-axillary line.
  • In aortic stenosis, A2 is soft. In aortic sclerosis, A2 is normal or noisy. Systolic murmurs in the elderly are quite common. They indicate heart disease and are associated with increased cardiac mortality.
  • Pulmonary regurgitation or aortic regurgitation produces an early diastolic murmur, as this is when the blood pressure is at its highest. An aortic regurgitation murmur is best heard using the diaphragm of the stethoscope with the patient seated forward with full expiration. Ask the patient to sit forward and put the stethoscope in place. Say, ‘Take a deep breath, take a good breath, and hold.’ This will give you a few seconds to hear the murmur. Few people can hold their breath for more than a few seconds, especially if they are not fit.
  • Not all murmurs come from valves. Some are flow murmurs where rapid flow during ejection causes turbulence, especially at the pulmonary or aortic outlet. This occurs in a hyperdynamic state as in anemia, severe thyrotoxicosis, or possibly with fever. It can also occur in pregnancy, but it is essential to exclude heart disease. The atrial septal defect flow murmur is described below.

Septal defects

  • Atrial septal defect with a significant left-to-right shunt will produce a pulmonary flow murmur. The murmur does not originate in the atria, and unless there is a significant shunt, there may be no murmur.
  • Ventricular septal defect produces a harsh systolic murmur, best heard along the left sternal border. It may be necessary to listen all the time to find it if it is small. There is little correlation between the size of the ventricular septal defect and the intensity of the murmur. Roger’s Maladie can be very loud and a silent massive flaw. It can be part of a more complex syndrome such as tetralogy of Fallot.

Other murmurs

  • Dilatation of the root of the pulmonary artery or aorta will cause a flow murmur. Syphilis aortic aneurysm or Marfan syndrome are some examples. These sounds are not transmitted well to the carotids, nor are they heard well at the vertex.
  • A patent ductus arteriosus causes a late systolic murmur in diastole. It is best heard through the back. There may also be a continuous machine murmur or a back and forth murmur in systole and diastole, but stronger in systole. Often clears the second heart sound.
  • The pericarditis produces an effect similar to that of boots trampling the snow and better heard in the left sternal edge sound.
  • The endocarditis infectious can be difficult to diagnose, but carries a high mortality and a change in the breath can be an important feature.
  • Prosthetic valves, such as the Starr-Edwards or modern variations, produce a very loud sound that can often be heard in a quiet room, without a stethoscope.

Whispers in children

  • Turbulence in the large veins can cause innocent venous tinnitus in very young children.
  • Heart murmurs in children are often innocent systolic flow murmurs and are common in children ages 3 to 8. They have an intensity of grade III or less and there is no abnormal physiology, such as impaired exercise tolerance. They tend to change in nature with changes in posture and can vary from exam to exam.

Differential diagnosis

The following is a very simple approach to differentiating some of the more common and simpler problems in identifying murmurs on auscultation:

  • Aortic stenosis, aortic sclerosis, and pulmonary stenosis (including effective pulmonary stenosis, as in the case of an atrial septal defect or hyperdynamic circulation), produce a decreasing-decreasing systolic murmur. Aortic stenosis transmits well to the carotids. Aortic sclerosis almost never occurs before age 50, and the patient is usually much older. It can be transmitted to the apex and axillary line. Pulmonary stenosis should not produce as flat a pulse wave as the others, and the murmur can reduce inspiration.
  • Mitral regurgitation begins early in systole and is a rough sound of almost constant amplitude, best heard at the apex and carried to the armpit.
  • Aortic regurgitation is early diastolic and is best heard in the aortic area with the patient seated forward on expiration. Only if the regurgitation is severe will a collapsing pulse and low diastolic blood pressure be found. Mitral stenosis is getting rarer these days. It is late diastolic and is best heard in the mitral area.
  • An innocent murmur in pregnancy is only systolic. It is a typical crescendo-decrescendo murmur that can be transmitted to the carotids. It can change with posture. There is a bounding pulse. There is no cardiac history, including shortness of breath during exertion. When in doubt, echocardiography provides a safe and reliable diagnosis.