Final answer:
The nurse should document the extra heart sound heard immediately after S2 as a third heart sound (S3), which can be associated with congestive heart failure.
Step-by-step explanation:
When a nurse hears an extra heart sound immediately after the second heart sound (S2), this sound should be documented as a third heart sound (S3). The S3 heart sound occurs during the rapid filling phase of ventricular diastole and may indicate conditions such as congestive heart failure. In the context of heart failure, the presence of an S3 sound is typically a sign of reduced ventricular compliance. The S1 heart sound corresponds to the closing of the atrioventricular valves and is the "lub" of the classic "lub-dub" of heart sounds, while the S2 corresponds to the closing of the semilunar valves and represents the "dub." An S4 heart sound happens just before S1, caused by atrial contraction pushing blood into the ventricle. Lastly, murmurs represent turbulent blood flow through the heart or its valves and are not directly related to the normal cycle of heart sounds.