The cardiovascular physical examination includes inspection, palpation, and auscultation of the heart as well as examination of the arterial and venous pulses. (See "Examination of the precordial pulsation" and "Examination of the arterial pulse" and "Examination of the jugular venous pulse".) The genesis of heart sounds continues to be a subject of debate and the precise mechanisms of their production have not been identified with certainty. This topic will review the auscultation of heart sounds. The auscultation of cardiac murmurs is discussed separately. (See "Auscultation of cardiac murmurs".)
A variety of stethoscopes are available for auscultation of heart sounds. Many stethoscopes have a separate bell and diaphragm. The bell is most effective at transmitting lower frequency sounds, while the diaphragm is most effective at transmitting higher frequency sounds.
Some stethoscopes combine these functions into a single surface such that the intensity of pressure of the stethoscope against the skin determines whether the stethoscope functions as a bell or a diaphragm. In addition, pressing the bell more firmly against the skin alters the frequencies that are loudest towards those of a diaphragm such that higher frequency sounds become louder and lower frequency sounds become softer.
FIRST HEART SOUND (S1)
The classic hypothesis for the genesis of the first heart sound (S1), for which there is much support, relates the high-frequency components of S1 to mitral and tricuspid valve closure; the first component of S1 is attributed to mitral valve closure and the second to closure of the tricuspid valve [1-4]. A second hypothesis suggests that the principal high-frequency elements of S1 are related to movement and acceleration of blood in early systole, and are influenced by the peak rate of rise of left ventricular (LV) systolic pressure (dP/dt), which is a measure of contractility and ejection of blood into the root of the aorta .
S1 occurs just before or coincident with the upstroke of the carotid pulse. Mitral valve closure precedes the upstroke of the carotid pulse because it occurs before LV ejection begins. However, the delay between mitral valve closure and the upstroke of the carotid pulse normally is too short to be appreciated at the bedside. Tricuspid valve closure normally coincides with the upstroke of the carotid pulse.