When performing a cardiovascular assessment, auscultation of heart tones is an important component of the examination. Each sound has different characteristics, including timing and intensity. Read on to find out more!
The Cardiac Cycle
The cardiac cycle starts with the beginning of one heartbeat to the beginning of the next heartbeat. Systole is the contraction that pushes blood from the ventricles. Blood from the right ventricle travels through the pulmonic valve to the lungs, whereas blood from the left ventricle travels through the aortic valve to the body. During systole, the tricuspid valve is closed preventing regurgitation of blood from the right ventricle into the right atrium. Likewise, the mitral valve is closed preventing regurgitation of blood from the left ventricle into the left atrium. It is the closure of the mitral and tricuspid valves that create the S1 heart sound.
As blood leaves the ventricles, the pressure drops within the chamber. During diastole, the tricuspid and mitral valves open to allow blood flow into the ventricles as the pulmonic and aortic valves are closed to prevent regurgitation from the pulmonary vein and the aorta, respectively. It is the closing of the pulmonic and aortic valves that create the S2 heart sound.
Splits (S1 split, S2 split)
An S1 split occurs when the earlier mitral and later tricuspid closure sounds separate. This can be a normal finding. During expiration, the aortic and pulmonic valves close nearly simultaneously creating a single sound of S2. An S2 split occurs occasionally on inspiration where the pulmonic valve slightly delays its closing. An S2 split can also be a normal finding.
Gallops (S3, S4)
An S3 gallop is sometimes heard after S2 due to deceleration of blood against the ventricular wall. This may be a normal finding in children, younger adults, and athletes. In older adults, however, this is considered pathological and may indicate heart failure.
The S4 heart sound would be heard immediately before S1 of the next beat. If present, this could be suggestive of ventricular stiffness and may be seen in those with hypertension or acute MI. In athletes, this may be a normal finding.
An opening snap may be heard as the mitral valve opens if there is restriction of the valve leaflets. This is heard just after S2 and could indicate mitral stenosis.
A clicking sound heard during systole may be indicative of mitral valve prolapse.
- When documenting S1 and S2 split sounds it is important to identify at what point during the respiratory cycle the sound is heard.
- In older adults, S3 and S4 heart sounds should be reported to the responsible provider.
- Systolic clicks are the most common extra heart sound.
Bickley, L. S., Szilagyi, P. G., Hoffman, R. M., & Soriano, R. P. (2021). Bate’s Guide to Physical Examination and History Taking (13th ed.). Wolters Kluwer Health: Philadelphia.