Gallops (S3 and S4)

In contrast to all of the other heart sounds so far, the gallops are low frequency events. They are much harder to hear and they are uniquely appreciated in the receiving ventricle of the pathology. For example, if you have a failing large LV and the LA is allowing blood to move into the LV causing this sound in the LV, you need to listen to the apex beat. If this is occurring due to a large failing RV, you would need to approximate the position of the RV apex, which is usually at the lower left sternal edge near the xiphoid process, to hear a right sided third heart sound. The other kind of gallop is the fourth heart sound, which is a presystolic sound. It precedes S1. The S3 is usually in the first half of diastole. Remember that S3 is a reflection of a failing ventricle or a volume overloaded ventricle such as in a ventricle of severe mitral regurgitation.

Demo of S3: you listen at the apex of the heart and hear a low frequency sound.

Demo of S4: also low frequency but it occurs right before S1.

Demo of S3 and S4 together: if the heart rate increases enough when you have both an S3 and an S4, you have a summation gallop. That is when S3 and S4 superimpose on each other, producing a loud single diastolic sound.

Hearing a third heart sound is an exceedingly important clinical observation. This is not found in normal individuals with the one exception of pregnancy. It’s found in very diseased ventricles and in very volume overloaded ventricles.

Category: Cardiology Notes