5 Areas for Listening to the Heart
First, identify cardiac auscultation sites. These include aortic, pulmonic, tricuspid, and mitral areas. Most normal heart sounds result from vibrations created by the opening and closing of the heart valves. When valves close, they suddenly terminate the motion of blood; when valves open, they accelerate the motion of blood. This sudden deceleration or acceleration produces heart sounds. Auscultation sites don’t lie directly over the valves but over the pathways the blood takes as it flows through chambers and valves.
Sound it out
Next, listen for a few cycles to become accustomed to the rate and rhythm of the sounds. You’ll differentiate heart sounds by their pitch (frequency), intensity (loudness), duration, quality (such as musical or harsh), location, and radiation. The timing of heart sounds in relation to the cardiac cycle is particularly important.
Two sounds normally occur: S1 and S2. They have a relatively high pitch and are separated by a silent period. Normal heart sounds last only a fraction of a second, followed by slightly longer periods of silence. Listen for:
- S1 — the lub of lub-dub — which occurs at the beginning of systole when mitral and tricuspid valves close and blood is ejected into the circulation
- S2 — the dub of lub-dub — which occurs at the beginning of diastole when aortic and pulmonic valves close (louder in the aortic and pulmonary chest areas), coinciding with the pulse downstroke and followed by a silent period that normally exceeds the pause between S1 and S2.