During which phase of the cardiac cycle is the aortic valve open?

The aortic valve is open during systole, which is the phase of the cardiac cycle when the ventricles contract. This contraction generates the pressure needed to propel blood into the aorta, allowing for effective blood flow to the systemic circulation. When the ventricle contracts, the pressure inside surpasses the pressure in the aorta, leading to the opening of the aortic valve and enabling blood to exit the heart.

During diastole, the heart chambers are filling with blood, and the aortic valve remains closed to prevent backflow into the ventricle. In isovolumetric contraction, although the ventricles are contracting, the pressure has not yet reached the level required to open the aortic valve, as both the aortic valve and mitral valve are closed. Atrial contraction occurs toward the end of diastole, primarily assisting in the filling of the ventricles but does not involve the opening of the aortic valve.

Thus, recognizing the mechanics of the cardiac cycle is crucial for understanding when the aortic valve opens, which occurs specifically during ventricular systole.