Heart Sounds and Heart Murmurs, Animation..

When a healthy heart beats, it makes a “lub-dub” sound. The first heart sound “lub”, also known as S1, is caused by the closing of the AV valves after the atria have pumped blood into the ventricles. The second heart sound “dub”, or S2, originates from the closing of the aortic and pulmonary valves, right after the ventricles have ejected the blood. The time interval between S1 and S2 is when the ventricles contract, called SYSTOLE. The interval between S2 and the NEXT S1 is when the ventricles relax and are filled with blood, called DIASTOLE. Diastole is longer than systole, hence the lub-dub, lub-dub, lub-dub…
Heart sounds are auscultated at 4 different sites on the chest wall which correspond to the location of blood flow as it passes through the aortic, pulmonic, tricuspid, and mitral valves, respectively. This is how SIMILAR defects associated with DIFFERENT valves are differentiated.
Heart murmurs are whooshing sounds produced by turbulent flow of blood. Murmurs are diagnosed based on the TIME they occur in the cardiac cycle, their changes in INTENSITY over time, and the auscultation SITE where they are best heard.