Where is S1 the loudest?

Where is S1 the loudest?

• A. Apex of the heart
• B. Base of the heart
• C. Left sternal border
• D. Right parasternal border

Answer: (A)

S1 is loudest where the mitral (and tricuspid) valve closures are closest to the chest wall, which is at the apex of the heart. The apex is the left fifth intercostal space at the midclavicular line, where the left ventricle lies closest to the chest wall. Because the vibrations from the mitral valve closing during the start of systole transmit most strongly to the chest wall there, S1 is maximally audible in this area. At the base, where S2 from the aortic and pulmonic valves is best heard, the mitral valve closure is farther away, so S1 is softer. The left sternal border and right parasternal border are typically used to listen for other sounds and murmurs rather than for the strongest S1.

S1 is loudest where the mitral (and tricuspid) valve closures are closest to the chest wall, which is at the apex of the heart. The apex is the left fifth intercostal space at the midclavicular line, where the left ventricle lies closest to the chest wall. Because the vibrations from the mitral valve closing during the start of systole transmit most strongly to the chest wall there, S1 is maximally audible in this area. At the base, where S2 from the aortic and pulmonic valves is best heard, the mitral valve closure is farther away, so S1 is softer. The left sternal border and right parasternal border are typically used to listen for other sounds and murmurs rather than for the strongest S1.