The second heart sound (S2) is produced by the closure ... Normally, A2 occurs just before P2, and the combination of these sounds make up S2. A physiologic split S2 occurs when the A2 sound ...

The fourth heart sound (S4), also known as the “atrial gallop,” occurs just before S1 when the atria contract to force blood into the left ventricle. If the left ventricle is noncompliant ...