Cardiogenic shock occurs when a weakened heart is suddenly unable to pump enough blood. "Shock" means that not enough blood and oxygen are reaching the brain and other organs. The most common cause of cardiogenic shock is a severe heart attack (myocardial infarction). This sudden blockage of coronary vessels can damage heart muscle, rupture the wall between the heart chambers and the outer heart wall, tear tendons that anchor heart valves, or disrupt or block heart rhythms. These serious complications of a heart attack affect the heart's pumping ability and can be fatal if not treated immediately. Other causes of heart damage leading to cardiogenic shock include: heart inflammation (myocarditis) or infection (endocarditis), severe arrhythmias, pericardial tamponade (accumulation of fluid in pericardial sac around the heart) and drug overdose.