Sudden cardiac arrest (SCA) occurs when the heart stops beating, suddenly and unexpectedly. When this happens the blood stops flowing to the brain and other vital organs. SCA is NOT a heart attack. A heart attack may cause SCA, but they are not the same. A heart attack is caused by a blockage that stops the flow of blood to the heart. SCA is a malfunction in the heart’s electrical system, causing the heart to suddenly stop beating.