A healthy heart typically makes two distinct sounds, often described as "lub-dub." These sounds are created by the closing of the heart valves.
The "Lub-Dub" Sounds
- "Lub" (S1): This high-pitched sound is caused by the closure of the mitral and tricuspid valves at the beginning of ventricular contraction (systole).
- "Dub" (S2): This second high-pitched sound is created by the closure of the aortic and pulmonic valves at the end of ventricular contraction. [Medicalnewstoday, 10-Aug-2022]
Additional Heart Sounds
While "lub-dub" is the most common and easily heard rhythm, there are also two quieter, lower-pitched sounds:
- S3: Sometimes heard as an extra "lub-dub-dup" sound; may indicate heart dysfunction. [Medicalnewstoday, 10-Aug-2022]
- S4: Sometimes heard as an extra "da-lub-dub" sound; may also indicate heart dysfunction. [Medicalnewstoday, 10-Aug-2022] These sounds are not always indicative of a problem but may warrant further investigation by a doctor.
Abnormal Heart Sounds: Murmurs
Other sounds, such as murmurs, may be present. Murmurs are often described as whooshing, swishing, or rasping sounds. They are caused by turbulent blood flow through the heart and can be a sign of several underlying conditions. [Mayo Clinic, Better Health Channel, BHF] The sound and location of a murmur can help doctors identify the potential cause. These sounds are distinct from the normal "lub-dub" and can be detected with a stethoscope.
Examples of abnormal sounds:
- Whooshing or swishing: Turbulent blood flow. [Mayo Clinic, Better Health Channel, BHF]
- Humming or rasping: Various potential causes requiring medical evaluation. [Better Health Channel]
The sounds described above are typically heard using a stethoscope. A normal heart beat, however, can also be heard without a stethoscope, though often faintly.
