Nothing astonishes men so much as common sense and plain dealing.
~ Ralph Waldo Emerson
Enjoy studying the common sense Cardio!
S3 - a ventricular gallop - produced by a blood flowing into an overly compliant left ventricle - "water rushing into a large reservoir" - dilated ventricle - one of the signs of CHF, HFrEF, MR, AR, high output states (thyrotoxicosis).
https://www.easyauscultation.com/cases/37/third-heart-sound-gallop