| Abnormal Sound | Description | Possible Cause | |----------------|-------------|----------------| | | Whooshing or swishing between lub and dub | Turbulent blood flow (e.g., leaky or narrow valve) | | S3 gallop | Extra sound after dub (“lub-dub-ah”) | Heart failure, volume overload (common in youth/pregnancy) | | S4 gallop | Extra sound before lub (“ah-lub-dub”) | Stiff ventricle (hypertension, heart attack history) | | Split S2 | “Dub” breaks into two distinct sounds | Delayed pulmonary valve closure (normal with inspiration) | 6. Takeaway Message The lub (S1) is the sound of the AV valves closing as the heart contracts to pump blood out. The dub (S2) is the sound of the semilunar valves closing as the heart relaxes to refill. Together, they create the familiar lub-dub rhythm of a healthy heartbeat. If you ever notice a different rhythm (like a swoosh, click, or extra beat), it doesn’t always mean something is wrong — but it’s worth discussing with a healthcare provider.