This demonstrates a physiological 3rd heart sound, which occurs between 0.09-0.21 seconds after the aortic valve closes. It is low-pitch in nature, and can cause what is termed a ‘gallop rhythm’. Whilst it is a normal variant in children and young adults, if found in patients over the age of 40-years, should be further investigated.

It is due to rapid ventricular filling, in either ventricle, in early diastole. If present in the left-side, it best hears in the left-lateral position, with the bell, in expiration. the right is heard best in inspiration at the left sternal edge.

It is abnormal when associated with conditions such as mitral valve regurgitation (otherwise known as incompetence).