The rhythmic sounds produced by the heart are a fundamental part of a health assessment, providing insights into the organ’s mechanical function. Listening to these sounds, a process known as auscultation, allows a healthcare professional to perceive the vibrations created by the closing of the heart’s valves and the movement of blood. These vibrations generate distinct sounds that reflect the heart’s pumping cycle and the effective operation of its components. The familiar “lub-dub” rhythm is a pattern created by the heart’s four valves snapping shut, a direct acoustic signature of the mechanical events regulating blood flow.
Essential Tools and Environment
The primary tool for listening to heart sounds is the stethoscope, which uses a chestpiece to transmit internal body vibrations to the listener’s ears. The chestpiece typically features two sides: the diaphragm and the bell, each designed to capture different sound frequencies. The diaphragm is the larger, flat side, which is best suited for hearing higher-pitched sounds, such as the normal “lub-dub” sounds (S1 and S2) and some regurgitant murmurs. This part works by filtering out lower frequencies and accentuating the shorter, sharper sounds generated by the closing valves.
The bell, conversely, is the smaller, cup-shaped side, which excels at detecting lower-frequency sounds that are often softer and deeper, like a third heart sound (S3) or certain types of murmurs. To properly use the bell, it should be applied to the skin with only light pressure; pressing too firmly will stretch the skin beneath it and cause it to act like a diaphragm, dampening the low-frequency sounds it is intended to capture. A quiet environment is important for effective auscultation, as ambient noise can easily mask subtle heart sounds. The stethoscope should be placed directly against the skin, as clothing interference can introduce artifact noise and distort the sounds being assessed.
Locating the Auscultation Points
Listening to the heart requires moving the stethoscope to four main auscultation points on the chest wall, which correspond to where the sounds from each valve are best transmitted. These points do not strictly align with the exact anatomical location of the valves but rather with the direction of blood flow and sound propagation. Finding these landmarks begins by locating the sternal angle, a slight ridge on the sternum that marks the level of the second rib.
The first location, the Aortic area, is found at the second intercostal space just to the right of the sternal border. Moving directly across the sternum to the left side, the second intercostal space marks the Pulmonic area. These two upper areas are referred to as the base of the heart.
Moving down the left sternal border to the fourth intercostal space identifies the Tricuspid area. The final point, the Mitral area, is located at the fifth intercostal space on the left side, following the line that runs down from the midpoint of the collarbone, known as the midclavicular line. This area is also known as the apex of the heart, where the heart’s strongest impulse can be felt.
Understanding the Standard Heart Sounds
The normal heartbeat is characterized by two primary sounds, S1 and S2, which create the repetitive “lub-dub” rhythm. The first heart sound, S1 (the “lub”), occurs at the beginning of ventricular contraction, or systole. This sound is produced by the simultaneous closure of the mitral and tricuspid valves, which separate the atria from the ventricles. The closure of these atrioventricular valves prevents blood from flowing backward into the atria as the ventricles expel blood.
S2, the “dub” sound, immediately follows S1 and marks the beginning of ventricular relaxation, or diastole. This sound is generated by the closure of the aortic and pulmonic valves, the semilunar valves that separate the ventricles from the large arteries. S2 is often heard as a higher-pitched sound than S1 and may split into two distinct components (A2 and P2) during inhalation, as the increased blood flow to the right side of the heart slightly delays the pulmonic valve closure. Listening at the apex (Mitral area) often makes S1 sound louder, while listening at the base (Aortic and Pulmonic areas) makes S2 more prominent, which helps differentiate the two sounds.
Identifying Deviations from Normal
Beyond the standard S1 and S2, the presence of additional sounds can indicate a deviation from normal blood flow or cardiac mechanics. These abnormal sounds can be broadly categorized into extra heart sounds and murmurs. Extra heart sounds include gallops, specifically S3 and S4, which are low-frequency sounds that occur during the rapid filling of the ventricles. S3, or a ventricular gallop, happens shortly after S2 and may indicate ventricular volume overload, while S4, an atrial gallop, occurs just before S1 and is often associated with a stiffened ventricle.
Murmurs are distinct from extra sounds and are characterized by a whooshing or swishing noise caused by turbulent blood flow through the heart or great vessels. This turbulence can result from blood flowing through a narrowed valve (stenosis), leaking backward through a valve that does not close completely (regurgitation), or passing through an abnormal opening in the heart wall. While a medical professional will grade a murmur based on its intensity and timing, the general public should recognize any atypical sound as a reason to seek professional medical assessment. Interpreting the precise cause and severity of these deviations requires specialized training.