The cardiac cycle is defined as the steps involving the conversion of deoxygenated blood to oxygenated blood in the lungs and pumping it by the heart to the body through the aorta. So i think it would be stable over the years unless u have factors that will affect the cycle depending on a persons health
It´s because of the lack of the gravity factor that´s present on the surface of Earth. This makes bodies and objects so light and they practically float in the station´s interior. Earth´s gravity is simply weaker the further you are from it.
