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In EMS, auscultation of the heart is often an overlooked assessment. It is largely due to lack of education and lack of an ideal environment for listening to heart tones. Auscultating heart sounds is generally not a required part of the primary or secondary assessment, however, taking the time to do so, as well as having the knowledge to accurately perform this assessment and recognize abnormalities can make a big difference in the outcome of a patient.


It is preferable to perform auscultation of the heart while on-scene in a quiet environment if possible. The back of the ambulance is noisy and there is a lot of movement, which makes it difficult to pick up heart sounds. To get the best results, have the patient sit up and lean slightly forward so that the heart is closer to the anterior chest wall. 

The sounds that are heard during auscultation are caused by the closure of the valves as the atria and ventricles contract. Normal heart tones are described as sounding like “lub-dub” and are referred to as S1 and S2. S1 represents the “lub” sound and is caused by the closure of the tricuspid and mitral (bicuspid) valves simultaneously, right before the contraction of the ventricles. S2  represents the “dub” sound and is the closure of the aortic and pulmonary valves simultaneously, at the end of a ventricular contraction. 

To properly auscultate for these sounds, you will need to place a stethoscope over the areas where each of the valves is located. To listen to the aortic valve, place the stethoscope to the right of the patient's sternum in the second intercostal space, as shown in figure 1. Move the stethoscope directly to the other side of the sternum to listen to the pulmonic valve. The fourth intercostal space, to the left of the sternum, corresponds with the tricuspid valve; and the fifth intercostal space, mid-clavicular, corresponds with the mitral valve.  

Abnormal Heart Sounds

In addition to the S1 and S2 sounds, some people may have an S3 or S4 sound, which is considered abnormal heart tones. S3 is a low pitched sound that is often called a gallop and occurs during the period that the ventricles are at rest (diastole). During the heart beat cycle with an S3 heart tone, it would sound like “lub-dub-da”. This abnormal heart sound is sometimes normal in younger people but is often a sign of left ventricular failure or distension. S4 is a medium pitched sound that occurs right before the S1 sound. With the S4 heart tone, the heart beat sounds like “blah-lub-dub”. This heart sound is alway abnormal and can indicate hypertension, coronary artery disease, or hypertrophic cardiomyopathy.


Murmurs are abnormal “whoosh-like” sounds that indicate turbulent flow through the valves of the heart. There are systolic and diastolic murmurs. Systolic murmurs, also known as ejection murmurs, are caused by an outflow obstruction of the valves. This can be a result of narrowing (stenosis) of the aortic and/or pulmonic valves.

Clicks and Snaps

High pitched clicking or snapping sounds are always associated with the rapid opening of the valves. This is usually the result of stenosis of the valves. If the clicking sound occurs shortly after the S1 sound, it is due to stenosis of the aortic or pulmonary valves. If it occurs shortly after the S2 sound, it is due to stenosis of the mitral or tricuspid valves. If the patient has an artificial valve, it will also have a clicking or snapping sound that will be unlike any other sound. 

Recognizing heart tones is a skill that takes practice and experience. However, it is worth the effort to try and learn how to do this assessment, because recognizing subtle heart tone abnormalities in a patient and getting them checked out by a doctor could make a difference in their overall health. 

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