Systolic blood pressure represents which phase of the cardiac cycle?

• A. Relaxation
• B. Contraction
• C. Isovolumetric relaxation
• D. Diastasis

Answer: (B)

Systolic blood pressure is the arterial pressure during ventricular contraction when the ventricles actively eject blood into the aorta. As the ventricles contract and the aortic valve opens, blood is forced into the aorta and arterial pressure rises to a peak—the systolic pressure. After that, the heart relaxes and arterial pressure falls. The brief isovolumetric contraction phase occurs when the ventricles are contracting but the aortic valve hasn’t opened yet, so little if any blood is ejected and arterial pressure doesn’t rise to systolic levels. Isovolumetric relaxation is the short period after the aortic valve closes, with the ventricle relaxing but no filling yet, and diastasis is a later phase of diastole when filling progresses.