A extremely well presented analysis of the S4 gallop. Travel’s book on auscultation states the same information as you have presented. I must add, Travel teaches that a normal phonocardiogram with extremely sensitive pickups will register a forth heart sound with a frequency in the inaudible range in late diastole that is generated by the normal left atrial contraction when the tested person is in NSR and the compliance of the LV is normal. It is when the compliance of the LV is abnormally high in a disease state and the patient is in NSR does the amplitude of the vibration caused by the in flow of blood into a noncompliant LV reach the threshold of audibility that the sound represents an abnormality. The sound now is called a S4 gallop. My point is that Travel makes a distinction between the term S4 heart sound registered on a phonocardiogram as normal and the audible sound detected with auscultation, the S4 gallop as abnormal.
