Which phase of the cardiac cycle produces the greatest amount of pressure?

• A. Systolic
• B. Diastolic
• C. Isovolumetric
• D. Atrial

Answer: (A)

Pressure in the ventricles peaks when they contract to eject blood. During the systolic phase, the ventricles generate enough force to overcome the afterload in the aorta and pulmonary artery, opening the semilunar valves and pushing blood out. This creates the highest intraventricular (and arterial) pressures in the cycle. In diastole, the heart is relaxed and pressures are low. Isovolumetric contraction raises pressure rapidly with all valves closed, but the peak reached is part of the same systolic event and does not exceed the peak achieved during actual ejection. Atrial contraction contributes only a small amount of pressure. Hence, systolic phase produces the greatest pressure.