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In healthy adults, there are two normal heart sounds, often described as a lub and a dub that occur in sequence with each heartbeat. These are the first heart sound (S 1) and second heart sound (S 2), produced by the closing of the atrioventricular valves and semilunar valves, respectively.
A third heart sound, S3 usually indicates an increase in ventricular blood volume. A fourth heart sound S4 is referred to as an atrial gallop and is produced by the sound of blood being forced into a stiff ventricle. The combined presence of S3 and S4 give a quadruple gallop. [1] The x-axis reflects time with a recording of the heart sounds.
Heart sounds result from vibrations created by the closure of the heart valves. There are at least two; the first (S1) is produced when the atrioventricular valves (tricuspid and mitral) close at the beginning of systole and the second (S2) when the aortic valve and pulmonary valve (semilunar valves) close at the end of systole. [4]
Upon auscultation of an individual with mitral stenosis, the first heart sound is usually loud and may be palpable (tapping apex beat) because of increased force in closing the mitral valve. The first heart sound is made by the mitral and tricuspid heart valves closing. These are normally synchronous, and the sounds are termed M1 and T1 ...
The closing of the mitral valve and the tricuspid valve constitutes the first heart sound (S1), which can be heard with a stethoscope. It is not the valve closure itself which produces the sound but the sudden cessation of blood flow, when the mitral and tricuspid valves close. [citation needed].
Most bruits occur only in systole, so the bruit is intermittent and its frequency dependent on the heart rate. Anything increasing the blood flow velocity such as fever , anemia , hyperthyroidism , or physical exertion , can increase the amplitude of the bruit.
The closure of the semilunar valves causes the second heart sound. The aortic valve , which has three cusps, lies between the left ventricle and the aorta . During ventricular systole , pressure rises in the left ventricle and when it is greater than the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle ...
The first heart sound is followed by a high-pitched holosystolic murmur at the apex, radiating to the back or clavicular area. [6] Its duration is, as the name suggests, the whole of systole. The loudness of the murmur does not correlate well with the severity of regurgitation.