Question

Use a Pressure (Y-axis) and Volume (x-axis) diagram of the cardiac cycle for a human Left ventricle. The output valve is semilunar (SL) and the input valve is atrioventricular (AV).  Indicate on the cycle where output and input valves are open (SLO, AVO) and closed (SLC, AVC).   Why is relaxation and buildup of pressure during systole iso-volumetric?  Show on the diagram what would happen if the AV valve leaked.

Answer 1

As the graph shows no change in volume but increase in pressure from B to C - this is Isovolumic contraction

Also from D to A - No change in Volume but decrease in pressure i- Isovolumic relaxation.

AV valve leak leads to Regurgitation to blood from Ventricle to atrium. Hence the shape of the graph changes. The above graph is for Mitral Regurgitation.