About Video

The recording is from an adult patient with normal cardiac findings taken from the apex area. Question 1: Does the first heart sound (S1) have one component or two components? Question 2: What components of the S1 are normally audible at the apex? The mitral component of the S1 is the usual component audible at the apex. However when two components are heard at the apex one must consider the possibility of the combinations of the M1 component with either the A1 or the T1. It is more common in the normal adult to hear a split S1 formed by M1 and A1 as opposed to M1 and T1. M1–T1 may be the cause of a split S1 in young patients or in patients with either abnormal tricuspid valve (redundant tricuspid valve, Ebstein’s malformation) or an enlarged right ventricle (due to volume overload as in atrial septal defect) with good right ventricular contractility. T1 is heard best over the lower sternal or xiphoid area. When the T1 is loud or when the right ventricle is enlarged, the T1 may be audible over the apex also. T1 component of the S1 typically tends to get exaggerated in intensity with inspiration. (1) In this patient, the rhythm of the groups of two consisting of the S1 and the S2 is easily recognized. The S2 is the louder and sharper higher frequency sound. The S1 is wider and somewhat softer than the S2 due to its lower frequency content. (2) Careful attention will reveal that one can actually recognize two distinct components in the S1 complex. These are formed by the M1 and the A1 components in this normal adult.