The heart contracts and relaxes with each heartbeat. The contraction part of this cycle is called systole (SIS to-le). The relaxation portion is called diastole (di-AS to-le). My doctor has mostly been concerned about my diastolic numbers being so high... I think it s different for everyone though. In some people with heart failure, the contraction function is normal but there s impaired relaxation of the heart. This affects the heart s lower, pumping chambers (the ventricles) specifically. If the relaxation part of the cycle is abnormal, it s called diastolic (di as-TOL ik) dysfunction. Because the ventricle doesn t relax normally, the pressure in it increases and exceeds what s normal as blood for the next heartbeat. (It s harder for all of the blood to go into the ventricle.) This can cause increased pressure and fluid in the blood vessels of the lungs. (This is called pulmonary congestion.) It can also cause increased pressure and fluid in the blood vessels coming back to the heart. (This is called systemic congestion.) People with certain types of cardiomyopathy (kar de-o-my-OP ah-the) may also have diastolic dysfunction.