Second heart sound

This presentation is about mechanism and abnormalities of second heart sound.

1. بسم الله الرحمن الرحیم

2. Second Heart Sound Mechanism and variations

3. S2 The second heart sound (S2) is due to the closure of aortic and pulmonary valves. It has two components: Aortic component (A 2) due to aortic valve closure. Pulmonary component (P 2) due to pulmonary valve closure. The aortic component (A 2) is followed by the pulmonary component (P 2). Normally , during expiration, both valves close almost simultaneously, and hence, second heart sound is single. During inspiration , the aortic valve closes early due to increased capacitance of pulmonary vascular bed while pulmonary wall closes late due to increase in right ventricular volume. This results in a physiological inspiratory splitting of second heart sound. Loudness of A 2 or P 2 is proportional to the respective pressures in aorta or pulmonary artery at the onset of diastole .

4. Variations in the Intensity of Second Heart Sound Wide Mobile Split Reversed (paradoxical) Splitting • Delayed electrical activation of right ventricle • Right bundle branch block • Ectopic from left ventricle • Prolonged right ventricular systole • Pulmonary stenosis • Pulmonary hypertension • Massive pulmonary embolism • Early aortic closure • Mitral regurgitation • Delayed electrical activation of left ventricle • Left bundle branch block • Ectopic from right ventricle • Prolonged left ventricular systole • Hypertension • Severe aortic stenosis • Hypertrophic cardiomyopathy • Patent ductus arteriosus • Severe left ventricular dysfunction • Early pulmonary valve closure • Tricuspid regurgitation • Early electrical activation of right ventricle • Wolff-Parkinson-White syndrome (type B)

5. Variations in the Intensity of Second Heart Sound Wide Fixed Splitting Single Second Heart Sound • Atrial septal defect • Severe pulmonary stenosis • Severe right ventricular failure • Severe aortic stenosis (absent or markedly attenuated A2) • Severe pulmonary stenosis (absent or markedly attenuated P2) • Tetralogy of Fallot