Does the SV node hold the maximum amount of blood at the end of atrial systole?

No, the sinoatrial (SA) node does not hold blood; it is responsible for generating electrical impulses that trigger heartbeats. The maximum amount of blood in the heart at the end of atrial systole is found in the ventricles, specifically during the phase known as end-diastolic volume (EDV). This is when the ventricles are filled with blood just before they contract.