Which phase of the cardiac cycle follows immediately after the beginning of the QRS wave?: (A) Isovolumic relaxation, (B) Atrial systole, (C) Diastasis, (D) Isovolumic contraction
Answer is D. Immediately after the QRS wave, the ventricles begin to contract, and the first phase that occurs is isovolumic contraction. Isovolumic contraction occurs before the ejection phase and increases the ventricular pressure enough to mechanically open the aoic and pulmonary valves.