shock caused by heart failure. The heart fails to pump blood effectively. For example, a heart attack (a myocardial infarction) can cause an abnormal ineffectual heart beat (an arhythmia) with very slow, rapid, or irregular contractions of the heart, impairing the heart's ability to pump blood, lowering the volume of blood going to vital organs. Cardiogenic shock can also be due to drugs that reduce heart function or an abnormally low level oxygen in the blood (hypoxaemia) caused, for instance, by lung disease. Whatever be the cause, blood vessels constrict and adrenalin-like substances are secreted into the bloodstream, increasing the heart rate. Treatment of cardiogenic shock is aimed at improving the heart's function. Shock after a heat attack is extremely serious. The mortality rate is over 80%.