Second heart sound should split in inspiration and become single in expiration. Single second heart sound, or variation in splitting such as fixed splitting or reverse splitting, i.e. split in expiration and single in inspiration indicate pathology. Added sounds such as S4 is pathological. S3 may be normal. Innocent heart murmurs could be systolic and diastolic such as in venous hum, but never purely diastolic.
Harsh murmurs indicate pathology.
The term innocent was first used by William Evans in 1943. Also known as normal, functional, inorganic, innocuous, dynamic or benign. Innocent heart murmurs are due to turbulent blood flow at the origin of the great vessels. Due to blood flow across the aortic valve. Heard best over the right upper sternal border.