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Ebook Bedside cardiology: Part 2

(BQ) Part 2 book "Bedside cardiology" presents the following contents: Second heart sound, third heart sound, ejection sound, non-ejection sound, murmur, innocent murmur and sound, is your patient in heart failure, clinical assessment: pulmonary hypertension, segmental approach in congenital heart disea, clinical approach - eisenmenger physiology,. | 15 Second Heart Sound S2 Mechanism During the closure of the semilunar valves clapping of the leaflets does not produce the sound. Sudden deceleration of the retrograde flow of the blood column in the aorta or pulmonary artery by the closed tensed valves set the vibration of the cardiohemic system. The high frequency components of this vibration produce the S2. Splitting Physiological Splitting Fig. 15-1 Left ventricular ejection begins and completes earlier than right ventricle. Thus aortic component A2 occurs 10 to 15 ms earlier than the pulmonary component P2 . One cannot appreciate two components unless the split is more than 30-50 ms. This causes the S2 single during expiration where the split is less than 15-20 ms. In inspiration the split is appreciable because P2 is delayed and A2 occurs earlier. Delayed P2 contributes 70 and early A2 30 for the inspiratory split. P2 is delayed because of the effect of inspiration on the aortic and pulmonary hang out time. Hang-out time is defined as the interval between the end of the ventricular ejection and closure of the semilunar valve. This time is longer in pulmonary artery than the aorta. Pulmonary hang out time may be up to 60 to 70 ms whereas aortic hang-out time may be below 20 to 30 ms. Semilunar valve is closed only when the pulmonary artery or aortic diastolic pressure crosses that of the respective ventricle. Pulmonary vasculature is more compliant than the systemic vasculature pulmonary vascular resistance is one tenth of that of aorta and pulmonary artery has less elastic recoil power than that of the aorta. Thus it takes a longer time for the diastolic pressure building up in the pulmonary artery than in the aorta for this cross over Fig. 15-2 . 116 Bedside Cardiology Expiration Inspiration lying posture Expiration lying posture Inspiration sitting posture Expiration sitting posture Fig. 15-1 Physiological splitting of S2. A During inspiration P2 is delayed and A2 occurs earlier. Inspiratory shifting of P2