Cardiac Cycle and Sounds Prof. K. Sivapalan

Cardiac Cycle and Sound Venous blood flows into the atria [collectors]. It fills the ventricles when relaxed - diastole. Ventricular contraction –systole- ejects blood into circulation [pump]. Cardiac cycle usually means ventricular cycle. 2013 Cardiac Cycle and Sound

Phases of Cardiac Cycle. When left ventricle begins contraction, aortic valve remains closed. Mitral valve closes when ventricular pressure exceeds atrial pressure. Isovolumetric contraction phase follows.[0.05 sec] Aortic valve opens when ventricular pressure exceeds aortic pressure. Ejection phase [0.25 sec]- Blood flows forwards due to the momentum created by the contraction even when ventricular pressure falls below aortic pressure. Aortic valve closes due to back flow caused by elastic recoil of aorta. Isovolumetric relaxation phase follows.[0.05 sec] Mitral valve opens when ventricular pressure falls below atrial pressure- filling phase. [0.45 sec.] 2013 Cardiac Cycle and Sound

Pressure changes in atria. a wave - atrial contraction. c wave - ventricular contraction, AV valves bulging and/or back pressure. v wave [raising] -venous blood flow in. v wave [fall] - blood flow into ventricles. 2013 Cardiac Cycle and Sound

Cardiac Cycle and Sound Volume changes. End systolic volume – 50 ml. Early diastole – filling due to venous pressure. Atrial systole adds last 30% filling. End diastolic volume is 120 ml. ECG, Heart sounds corrilated. 2013 Cardiac Cycle and Sound

Muscles and Valves in Heart. All four valves are in the fibrous skeleton. Muscles above the skeleton [right] are atria and on the other side ventricles. 2013 Cardiac Cycle and Sound

Cardiac Cycle and Sound Apex Beat During ventricular contraction, apex remain in place and thrusts on the chest due to rotation. The fibrous ring moves left and right. 2013 Cardiac Cycle and Sound

Surface anatomy of the heart. Atria are right to the sternum. Right ventricle is anterior. Left ventricle is posterior with one cm above R. ventricle. Apex: fifth intercostal space, 1 cm medial to MCL All valves are placed in oblique plane. 2013 Cardiac Cycle and Sound

Cardiac Cycle and Sound Heart sounds. Normal heart sounds are produced by vibrations caused by closure of the valves. Mitral and tricuspid valves- 1st sound. Aortic and pulmonary valves- 2nd sound. Rapid filling – 3rd and 4th sounds. Sounds from each valve is best heard at different places on the chest. 2013 Cardiac Cycle and Sound

Cardiac Cycle and Sound Abnormal heart sounds. 2013 Cardiac Cycle and Sound