Next, we shall listen together at the apex. We'll use the bell of the stethoscope, we shall use light pressure on the bell and we shall place immediately over the apical impulse. We'll use the cotton swab, so that we can identify systole by the movement of the tip of the cotton swab on the carotid. Let's listen together. [Cut-away]
Choose the best description of the events at the time of the first sound: