This often indicates "regurgitation" (blood leaking backward) or "stenosis" (a valve that has become too narrow or stiff).
The first sound Lub ever heard was Dub.
When you place a stethoscope to a chest or even press your ear against a loved one’s heart, you don’t hear a single, steady drone. Instead, you hear a rhythmic, two-part beat: lub and dub sound
“Dub?” Lub’s pulse wavered.