exam 3: cardiac cycle & murmurs

Explain what is happening during cardiac cycle

• Late diastole contraction causes a rise in pressure in both the LA and LV

• After a short delay (when LV starts to contract), the LV pressure rises & the LV pressure exceeds the LA pressure. The MV closes & produces the first heart sound (S1)

• LV pressure becomes greater than aortic pressure & the AOV opens (silent event in normal heart)

• After contraction (ventricles relaxes) the pressure drops below aortic pressure, causing AOV to close & produces the second heart sound (S2)

Wigger’s Diagram

Pressure relationship between L sided heart chambers

• diagram shows which chamber has the highest pressure at different times & that determines whether valves open or close

Systole

Ventricular contraction

Diastole

Ventricular relaxation and filling

Wiggers Diagram- Late diastole (atrial systole)

What happens?

• The atrias are accepting blood returning to the heart from the systemic veins & pulmonary veins. Blood then passes from atrias to ventricles through the open AV valves (MV & TV) which then increases the diastolic pressure

• Late diastole (atrial contraction) pushes the last bolus of blood into each ventricle which gives rise to atrial and ventricular pressures creating the “a” wave