Reverse splitting occurs in conditions such as aortic stenosis (LBBB, HOCM). The splitting is fixed in Atrial septal defect (ASD). There may be a persistent or a widened splitting of S2 due to delayed right ventricular emptying, in diseases like pulmonary stenosis, right bundle branch block (RBBB), mitral regurgitation, and ventricular septal defect. Since this phenomenon is a normal occurrence it is known as a physiological splitting of S2. This occurs because of an increased venous return and decreases pulmonary vascular resistance. During inspiration, there is a delay in the closing of the pulmonary valves by about 30 to 60 milliseconds. The splitting is best heard in the second left intercostal space and the left sternal edge. The pulmonary component of S2 is known as P2, whereas the aortic component is called A2. This is because of the lower pressures in the pulmonary circulation allowing the blood to continue flowing into the pulmonary artery after systole ends in the left ventricle. Normally the aortic valves close before the pulmonary valves close. Increased intensity is heard in systemic hypertension (aortic component) and pulmonary hypertension(pulmonary component). When compared with the first heart sound, S2 is shorter, softer and is slightly higher pitched. Although it is heard over the precordium, S2 is loudest at the base (left sternal edge).ĭecreased intensity heard in low cardiac output, calcified aortic stenosis, and aortic incompetence. The aortic component of the second sound (A2) Slightly precedes the pulmonic component (P2). The second heart sound (S2) occurs with the closure of the semilunar valves (aortic and pulmonary valves) and signals the end of systole. Its intensity is increased in mitral stenosis due to an increased left atrial pressure and decreases in low cardiac output conditions. You can hear S1 over all the precordium but its usually loudest at the apex. The mitral component of the first heart sound (M1) Slightly precedes the tricuspid component (T1), but you usually hear the two components fused as one heart sound. The first heart sounds (S1) occur with the closure of the atrioventricular valves (mitral and tricuspid valves) and thus it signals the beginning of systole. Normal Heart Sounds The first heart sounds (S1) In some instances, extra heart sounds may be heard, these are the third and fourth heart sounds and additional sounds known as heart murmursĮvents in the cardiac cycle generate sounds that can be heard on the surface of the chest wall. These are the first heart sound and second heart sounds. 45(6), 285 (1998).During auscultation, two normal heart sounds are heard from a person with a normal heart. J. Chin, Acta Cardiologica XLIII, 337 (1993). Electronic magister thesis of signals and systems, Departement of Electronics, Faculty of Science Engineerig, University Aboubekr belkaid Tlemcen, Algeria, 18–24, 1999. Djebbari A., Synthèse des méthodes d'analyse temporelle, spectrale et spectrotemporelle du signal phonocardiogramme.B. Tuteur, Wavelet Transforms in signal detection, IEEE ICASSP ( 1988) pp. Grossman A., Morlett J., Decomposition of Function into Wavelets of Shape and Related Transforms, Center for Interdisciplinary Research and Research Center Biefeld-Bochum, University of Biefeld, Report No.R. Olivier and P. Duhamel, IEEE Transactions Information Theory 38(2), 569 (1992).Luisada, The sounds of the normal heart ( WH, Green, St Louis, 1972 ).
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