"Mapping" the precordium. I. Heart sounds of normal subjects.

Abstract A systematic study of the amplitude of the heart sounds was made in 30 normal subjects (10 young men, 10 young women, and 10 children). It was based on the graphic recording of the amplitude of the main component of the first heart sound, the aortic component of the second heart sound, and the pulmonary component of the second heart sound. Special attention was paid to the exact constancy of amplification and condition of recording. Tracings were recorded over eight precordial areas. The first heart sound was found generally largest over the left parasternal areas; exceptions were represented by cases having a largest first sound at the apex, at the fifth sternal or fourth right parasternal area, or even at the second right space. No basic difference existed in the maximal amplitude and spread of the first two components of the first sound. The aortic component of the second heart sound was found largest generally in the third left parasternal area. Exceptions were represented by cases having a largest aortic component over the second or fourth left parasternal area. The third and fourth sounds, when recorded in children, had maximal amplitude in the left parasternal areas. These data confirm a recent systematization of the auscultatory areas of the precordium but are in contrast with older views on the classic areas of auscultation of the heart.