From the Research
S1 (first heart sound) is best heard at the apex of the heart, specifically at the mitral area (5th intercostal space, midclavicular line) and the tricuspid area (4th intercostal space, left sternal border), while S2 (second heart sound) is best heard at the base of the heart, particularly at the aortic area (2nd intercostal space, right sternal border) and the pulmonic area (2nd intercostal space, left sternal border). The locations where S1 and S2 are best heard correspond to where the sounds originate: S1 is produced by closure of the mitral and tricuspid valves at the beginning of ventricular systole, while S2 results from closure of the aortic and pulmonic valves at the end of ventricular systole 1. When auscultating the heart, it's essential to listen at all these areas systematically to properly evaluate both heart sounds. Some studies have investigated the use of digital stethoscopes and signal analysis to detect and characterize S1 and S2, including a study that found the P2:A2 and P2:S2 intensity ratios to be significantly different between subjects with and without pulmonary artery hypertension 2. However, the most straightforward and clinically relevant approach to hearing S1 and S2 remains auscultation at the specified locations. Key points to consider when evaluating S1 and S2 include:
- The intensity of the sounds
- The splitting of S2
- The presence of any additional sounds, such as S3 or S4
- The relationship between S1 and S2 and other cardiac sounds or murmurs. Auscultation of the heart is a crucial skill for healthcare professionals, and being able to accurately identify and interpret S1 and S2 is essential for diagnosing and managing cardiac conditions 3, 4, 5.