Clinical Quick Reference Monthly / August 2022 / Heart Sounds – Cardiac Auscultation
Clinical Quick Reference Guides Concept Review/Heart Sounds
This overview will help clarify the basic heart sounds, providing an introduction to the fundamentals involved in cardiac auscultation.
What Are the Heart Sounds?
In the scientific study of physics, sound is defined as a vibration which propagates as an acoustic wave, transmitting through a medium (for example: a gas, liquid or solid). Students of human anatomy and physiology recognize that sound is the reception of those distinct waves and their subsequent perception by the brain.
“Heart sounds” are created as blood flows through the heart chambers. The beating heart, the resultant flow of blood through it, and the heart valves snapping shut, all create very particular sounds. In general, the more turbulent the blood flow, the greater the vibration generated.
In cardiac auscultation, an examiner may use a stethoscope to listen for these unique sounds.
Study of a patient’s heart sounds with a stethoscope is a basic component of any thorough medical exam. Auscultated sounds may indicate general heart health, while others are very characteristic of pathological issues.
Tip: Remember, sound will be transmitted in the same direction as blood flow*
Basic Cardiac Auscultation
Cardiac auscultation was long considered to be a centerpiece of cardiac examination. Listening to the heart requires that the clinician, or examiner, has excellent hearing. In addition, the clinician also needs to be able to distinguish between subtle differences in pitch and timing.
What Equipment Is Required?
In order to perform a basic assessment of a patient’s heart sounds, the clinician will need a stethoscope and a watch/clock with second hand.
Core Knowledge
Cardiac Valves
There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle. Atrioventricular valves are located on the floor of the atria and empty into the ventricles. Semilunar valves separate the ventricles from the great arteries.
The main job of the heart valves is to permit the forward flow of blood and prevent its backward flow.
Flow
Blood flow can be laminar or turbulent. Laminar flow is smooth and is generally associated with less/or low resistance. Turbulent flow is the opposite of this. It is generally associated with increasing levels of resistance and is more chaotic.
It is important to note that heart sounds may be altered by dysfunction or deformities of the valves, producing various types of murmurs (series of vibrations of variable duration). The clinician must take care to distinguish the physiologic heart sounds from them, should one be present.
Physiologic Heart Sounds
The “S1, S2” Sounds That We Expect to Hear
The standard rhythm of a beating heart sounds a little like: lub-dub, lub-dub, lub-dub. Pretty standard, right?
But, what do those sounds actually represent? What is the clinician listening for? What is going on in the patient’s heart?
Let’s take a closer look at the physiologic heart sounds.
The S1 Heart Sound
An “S1” heart sound is produced as the mitral and tricuspid valves close in systole
This is the 1st heart sound.
It represents the “lub” in the heart’s characteristic “lub-dub” rhythm
It is a softer, lower pitched sound than S2 (lasts approx. 0.10 – 0.17 secs)
The S2 Heart Sound
An “S2” heart sound is produced with the closing of the aortic and pulmonic valves in diastole
This is the 2nd heart sound.
It represents the “dub” in the heart’s characteristic “lub-dub” rhythm
It is shorter, sharper and higher pitched (lasts approx. 0.10 – 0.14 secs)
What Happens When The Clinician Hears lub-dub-dub?
What about the S3 and S4 Heart Sounds?
The third and fourth heart sounds (S3 and S4) are two unusual heart sound components. They are often indicators of heart failure. An S3 sound can be normal at times, but may be pathologic. Further examination should be performed to identify the nature of its presence.
S4 heart sounds are almost always pathologic.
The S3 heart sound is a low-frequency, brief vibration occurring in early diastole at the end of the rapid diastolic filling period of the right or left ventricle. It may be noted in the patient’s chart as a: ventricular gallop, early diastolic gallop, ventricular filling sound, or protodiastolic gallop.
The S4 heart sound is a presystolic heart sound commonly associated with reduced ventricular compliance. Its sound is usually generated by a stiffened ventricle (low ventricular compliance), and therefore is heard in patients with ventricular hypertrophy, myocardial ischemia, or older adults.
Where To Start?
In cardiac auscultation, an examiner may use a stethoscope to listen for the unique and distinct sounds associated with the heart beat and its rhythm.
The heart is located just behind and slightly left of the breastbone, between the 4th and 6th ribs. A basic examination may begin by placing the diaphragm of the stethoscope on the skin. The clinician can listen to the heartbeat, and may move the chestpiece of the stethoscope around a little to listen for the loudest spot.
The normal heartbeat sounds like ‘’lub-dub,’’ as the heart contracts.
Remember for S3 & S4 heart sounds, they are rarely heard after age 40 as a normal finding and follow closely after S2.
These sounds usually have a lower frequency, best heard with the bell of the stethoscope pressed lightly to the apex, with the patient in the left lateral position.
Medical Terminology
Getting to know these terms will help reinforce the above material.
auscultate – to examine patients by listening to sounds; typically using a stethoscope
stethoscope - instrument useful in auscultation which conveys the sounds from the body of a patient to the ear of the user
bell (stethoscope) – elongated portion of the chestpiece that is used to listen for and evaluate lower pitched noises and sounds
diaphragm (stethoscope) – round portion of chestpiece that often has a disc (thin membrane); this portion of the stethoscope is highly sensitive and useful in picking up higher pitched noises and sounds.
Anatomy & Physiology
Becoming familiar with these body systems will help increase understanding of body processes and medical conditions.
heart valves
heart valves control blood flow in, through and out of the heart
aortic valve (lies between the left ventricle and the aorta)
mitral valve (lies between the left atria and the left ventricle)
pulmonary valve (lies between the right ventricle and the pulmonary artery)
tricuspid valve (lies between the right atrium and the right ventricle)
Helpful Video:
To help differentiate between physiologic heart sounds and murmurs:
Disclaimer: The above study guide represents study materials, always seek and follow the advice of your medical provider for any acute or chronic medical issues or questions.