S1, S2, S3, S4 Heart Tones

For us, working in the prehospital setting, listening to all the heart tones may be not as desired, as it is in the hospital setting. Yet, it is still important to understand heart tones. By understanding these, one will be able to figure out if their is an issue with the aortic valve, pulmonic valve, tricuspid valve, and the bicuspid valve.

By knowing what is normal sounding, will make abnormal sounds easier to identify. If an abnormal sound is detected, it is possible that the valve is failing in some way. A failing valve can be fatal to patients. In some cases, patient's may live with an abnormal sounding valve (valve issues), and have no side effects of the valve, until the valve fails to point where they need surgery to fix the failing valve.

In addition, their are many great videos on youtube® to help explain heart tones, S1, S2, S3, S4 a whole lot more and with more detail.


Let's break down what each valve does.
   -Aortic Valve
       >Valve that allows blood to enter into the aorta
   -Pulmonary Valve
       >Valve that allows blood to enter into the pulmonary arteries
   -Tricuspid Valve
       >Valve that allows blood to enter the right ventricle from the right atrium
   -Bicuspid Valve
       >Valve that allows blood to enter the left ventricle from the left atrium

Now, let's go over S1, S2, S3, S4 heart sounds.
   -S1
       >First heart sound, heard
       >"lub" of lub-dub
       >Caused by the sudden block of reverse blood flow due to closure of the AV valves
       >Beginning of ventricular contraction (systole)
   -S2
       >Second heart sound, heard
       >"dub" of lub-dub
       >Caused by the sudden block of reversing blood flow due to closure of the semilunar valves
       >End of ventricular systole and beginning of ventricular diastole
   -S3
       >Rarely heard, but can still be present
       >Considered the "third" heart tone
       >AKA protodiastolic gallop, ventricular gallop
       >AKA the "Kentucky" gallop
            =Caused by stress of S1 followed by S2 and S3 together
            =S1-"Ken" ; S2-"tuck" ; S3-"y"
       >Occurs are the beginning of diastole after S2, but lower pitch than S1 or S2
            =This is because it is not of valvular origin
       >Usually occurs later in life, and can signal cardiac problems
            =CHF
       >Caused by the oscillation of blood back and forth between the walls of the ventricles
   -S4
       >Rarely heard
       >Considered the "fourth" heart tone
       >AKA presystolic gallop or atrial gallop
            =Produced by blood being forced into a stiff hypertrophic (enlarged cells) ventricle
       >AKA "Tennessee" gallop
            =S4-"Ten-"
            =Best heart at the apex, while patient is holding their breath, while supine
       >Signals a failing or hypertrophic (enlarged cells) in the left ventricle, systemic HTN
            =Others: Valvular aortic stenosis, hypertrophic cardiomyopathy (heart muscle is enlarged)
       >Occurs just after atrial contraction, immediately before S1
       >Side note: atrial contraction must be present for production of S4
            =Not present in atrial fibrillation
            =Or in other rhythms where atrial contraction does not precede ventricular contraction