The pulmonic valve may close after the aortic, as the right ventricle can fill with more blood, leading to a slightly longer ejection time.ĭoctors may also refer to the second heart sound as an S2, and if there is a time difference in the closure, it is a split 2. If the aortic valve closes before the pulmonic valve, it may cause two distinct sounds, which experts may refer to as aortic and pulmonic components. The valves close, which causes vibrations, and results in the second “dub” sound. The second sound occurs when the ventricles relax to receive blood from the atria after pumping blood, which is the diastole phase of the cardiac cycle. Split heart sounds may indicate a problem. A split S1 occurs when the time difference between the two valves increases. Clinically, this noise corresponds to the pulse, and doctors refer to it as S1. As the valves close almost simultaneously, it usually creates a single sound. These valves close to prevent blood from flowing into either atrium after the two ventricles contract to pump blood into the pulmonary artery and aorta.Īs the valves close, this creates an audible vibration as the first heart sound. Vibrations from closing the two valves known as the mitral and tricuspid valves cause the first “lub” heart sound. Sometimes, if the doctor can hear the third and fourth sounds, it may indicate a potential problem with heart function. The third and fourth sounds are low pitched and often quieter. It is much easier to hear the first two noises, “lub” and “dub,” which are high pitched. The former is when the ventricles contract and pump blood out, and the latter is when the ventricles relax and fill with blood. There are two phases in the cardiac cycle: systole and diastole. Valves at the bottom of each atrium empty into the two ventricles. Heart sounds refer to the noises that occur when blood flows through the heart chambers as valves open and close during the cardiac cycle. Share on Pinterest NICK VEASEY/SCIENCE PHOTO LIBRARY/Getty Images
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