Lena Torres
Heart sounds are the noises generated by the beating heart and the flow of blood through it. They are created from blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations from these structures create audible sounds, with the turbulence of blood flow influencing the strength of the sound. Heart sounds can be described by their intensity, pitch, location, quality and timing in the cardiac cycle. They are a valuable tool in evaluating a patient's heart health and diagnosing pathologic cardiac conditions.
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What You'll Learn
- Heart sounds are made by blood flowing through the heart chambers
- The cardiac cycle has two phases: systole and diastole
- Heart valves closing create vibrations that make audible sounds
- Heart murmurs are caused by turbulent blood flow
- Heart sounds can be described by their intensity, pitch, location, quality and timing
Heart sounds are made by blood flowing through the heart chambers
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. The heart has four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. Heart sounds are made by blood flowing through these chambers as the cardiac valves open and close during the cardiac cycle.
The cardiac cycle features four sounds. The first two noises, "lub" and "dub", are high-pitched and easier to hear. The third and fourth sounds are low-pitched and often quieter. Sometimes, if a doctor can hear the third and fourth sounds, it may indicate a potential problem with heart function. The first heart sound, or S1, forms the “lub” sound and is composed of mitral valve closure (M1) and tricuspid valve closure (T1). The second heart sound, or S2, forms the “dub” sound and is produced by the closing of the semilunar valves.
The rarer extra heart sounds form gallop rhythms and are heard in both normal and abnormal situations. The third heart sound, or S3, is rarely heard and is also called a protodiastolic gallop, ventricular gallop, or informally the "Kentucky" gallop. The fourth heart sound, or S4, is an abnormal late diastolic sound caused by forcible atrial contraction in the presence of decreased ventricular compliance. The combined presence of S3 and S4 is a quadruple gallop, also known as the “Hello-Goodbye” gallop.
The heart sounds are created from vibrations of cardiac structures caused by changes that create turbulent flow. The more turbulent the blood flow, the more vibrations that are created. These vibrations from the blood flow create audible sounds. Heart murmurs are produced as a result of turbulent flow and can be heard in different parts of the cardiac cycle, depending on the cause.
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The cardiac cycle has two phases: systole and diastole
The heart creates audible sounds as blood flows through its chambers and the cardiac valves open and close during the cardiac cycle. The cardiac cycle involves four major stages of activity: "isovolumic relaxation", inflow, "isovolumic contraction", and "ejection". The first two stages comprise the diastolic phase, while the last two stages make up the systolic phase.
Diastole, or the diastolic phase, is when the heart chamber is in a state of relaxation and fills with blood returning from the veins. During this phase, the heart relaxes and expands while refilling with blood returning from the circulatory system. Both atrioventricular (AV) valves open to facilitate the flow of blood directly through the atria into both ventricles. Atrial systole occurs near the end of diastole, when the atria begin contracting and pumping blood into the ventricles. This phase is also called the ventricular diastole period. The third heart sound, or S3, occurs during diastole and is usually benign, but if it re-emerges later in life, it may signal cardiac problems.
Systole, or the systolic phase, is when the heart chambers contract and pump blood towards the periphery via the arteries. During this phase, the ventricles contract, and the pressure within the ventricles becomes greater than that of the adjacent blood vessels, allowing blood to flow out. The first heart sound, or S1, occurs at the beginning of systole and is caused by the closure of the atrioventricular valves. The second heart sound, or S2, occurs at the beginning of diastole and is caused by the closure of the semilunar valves.
The cardiac cycle is a series of pressure changes within the heart that result in blood movement through its chambers and the body. These pressure changes are caused by conductive electrochemical changes within the myocardium that lead to the concentric contraction of cardiac muscle. The cardiac cycle, or heartbeat, typically takes about 0.8 seconds to complete.
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Heart valves closing create vibrations that make audible sounds
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. The heart has four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. The atrioventricular valves are located on the floor of the atria and empty into the ventricles.
Heart sounds are produced from a specific cardiac event, such as the closure of a valve or the tensing of a chordae tendineae. The vibrations of these structures from the blood flow create audible sounds. The more turbulent the blood flow, the more vibrations are created. The turbulence of blood flow is determined by fluid viscosity, density, velocity, and the diameter of the column through which the fluid is traveling.
The first heart sound, or S1, forms the "lub" of "lub-dub" and is composed of mitral valve closure (M1) and tricuspid valve closure (T1). The mitral and tricuspid valves close almost simultaneously, creating a single sound. The second heart sound, or S2, forms the "dub" and is produced by the closing of the semilunar valves. The third heart sound, or S3, is rarely heard and is also called a protodiastolic gallop. It occurs at the beginning of diastole after S2 and is lower in pitch than S1 or S2. The fourth heart sound, or S4, is an abnormal sound that can be heard immediately before S1 and indicates increased resistance to ventricular filling due to high atrial pressure or increased ventricular thickness.
In addition to these normal sounds, a variety of other sounds may be present, including heart murmurs, adventitious sounds, and gallop rhythms. Murmurs may be physiological (benign) or pathological (abnormal). Heart murmurs are produced as a result of turbulent flow of blood strong enough to produce audible noise.
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Heart murmurs are caused by turbulent blood flow
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. The sounds are created from blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations of these structures from the blood flow create audible sounds. The more turbulent the blood flow, the more vibrations are created.
Innocent heart murmurs can be caused by changes in blood flow due to growth spurts or anemia, which affects blood viscosity. They can also be caused by carcinoid syndrome or carcinoid heart disease, a slow-growing tumour that can affect the heart. Innocent murmurs can disappear and reappear and may get louder when the heart beats faster.
Other heart murmurs may be a sign of a serious heart condition and can be caused by problems with the aortic or mitral valves, such as aortic regurgitation, aortic stenosis, mitral regurgitation, or mitral stenosis. They can also be caused by calcium deposits, which can cause a heart valve to become stiff and narrow (valve stenosis) or not close completely, allowing blood to flow backward. In addition, bacterial or other germs can cause an infection of the inner heart lining and valves (endocarditis), which can spread through the blood to the heart from another part of the body, such as the mouth.
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Heart sounds can be described by their intensity, pitch, location, quality and timing
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. They can be described by their intensity, pitch, location, quality and timing.
The intensity of a heart sound is influenced by the amount of pressure that forces the valve closure. For instance, in mild to moderate mitral stenosis, the increased left atrial pressure causes the mobile portions of the mitral valve leaflets to be more widely separated, resulting in an accentuated M1 sound. In severe cases of mitral stenosis, the valve leaflets are so calcified and immobile that the M1 sound is diminished or absent. The ventricular contraction rate also affects the intensity of the first heart sound. The faster the heart rate and the faster the rise in ventricular pressure, the louder the sound.
The pitch of a heart sound can be described as high or low. The first and second heart sounds, often described as "lub" and "dub", are high-pitched. The third and fourth heart sounds are low-pitched and quieter. Low-pitched sounds can be heard using the bell attachment of a stethoscope.
The location of a heart sound can help determine its etiology. For example, the first heart sound is best heard at the tricuspid (left lower sternal border) and mitral (cardiac apex) listening posts. The third heart sound is best heard with the bell side of the stethoscope, which is used for lower-frequency sounds. A left-sided third heart sound is best heard at the apex of the heart, normally located in the 5th left intercostal space at the midclavicular line. A right-sided third heart sound is best heard at the lower left sternal border.
The quality of a heart sound refers to its characteristics, such as whether it is described as a "click", "snap", "knock", or "gallop". These terms may not have specific meanings, but they can be referenced when describing the sound.
The timing of a heart sound can be described as occurring during early, mid, or late systole, or early, mid, or late diastole. The first heart sound occurs during systole, while the second heart sound occurs during diastole. The third heart sound occurs during early diastole, and the fourth heart sound occurs during late diastole.
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Frequently asked questions
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it.
Heart sounds are created from blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations of these structures from the blood flow create audible sounds.
The two normal heart sounds are often described as a "'lub' and a 'dub' that occur in sequence with each heartbeat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the atrioventricular valves and semilunar valves, respectively.
The third heart sound (S3) and fourth heart sound (S4) are rarer extra heart sounds. S3 is rarely heard and is also called a protodiastolic gallop. S4 is an abnormal late diastolic sound caused by forcible atrial contraction in the presence of decreased ventricular compliance.
Heart sounds are usually heard using a stethoscope. Doctors can use the diaphragm attachment to hear higher-pitched noises and the bell attachment to listen for lower-pitched sounds.
