S1 occurs almost simultaneously with the carotid artery upstroke . Clinicians often palpate the pulse while listening to identify S1. How to Listen (Auscultation)

If you’ve ever listened to a heartbeat through a stethoscope, the familiar “lub-dub” rhythm is the sound of heart valves closing. The first part of that rhythm—the —is known clinically as the S1 heart sound .

The S1 heart sound, colloquially known as the is the acoustic signal marking the beginning of ventricular systole —the phase where the heart contracts to pump blood.

Next time you listen to a chest, remember: The "Lub" is the sound of your heart securing the exit routes before sending blood to the body! 🩸