He initial vibrations occur when the first contraction of the ventricle move blood towards the atria, closing the av-valves. The second component is caused by the abrupt tension of the closed av-valves, decelerating the blood.
Answers
Definition
Heart sounds are discrete bursts of auditory vibrations of varying intensity (loudness), frequency (pitch), quality, and duration. The first heart sound (S1) is composed of several high-frequency components; only the first two are normally audible. These two sets of audible vibrations are temporally related to closure of the mitral and tricuspid valves. The first heart sound coincides with contraction of the ventricles, thus identifying the onset of ventricular systole and the end of mechanical diastole.
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Technique
The examination should be conducted in a warm, quiet room. Place the patient in a supine position after all clothing has been removed from the chest. Explain to the patient that you are going to examine the heart. Warm your hands and stethoscope, but warn the patient that your hands may be cool at first. The most comfortable and satisfactory position for most examiners is on the patient's right side. Since heart sounds may be palpable, attempt to palpate the first sound with the heel of the right hand and/or the fingerpads, initially at the cardiac apex and then over the entire precordium.
The acoustic events should be analyzed only after having assessed the venous, arterial, and chest wall pulsations. The auscultatory examination is commonly begun at the aortic area (second right intercostal space) and the stethoscope inched to the pulmonary area (second left intercostal space), the tricuspid area (lower left sternal border), and mitral area (cardiac apex), as shown in Figure 22.1. Follow an identical routine for every examination, passing from one part to another in a particular order.