This occurs when the pumping action of the heart stops, either because it stops beating (see ASYSTOLE) or because the heart muscle contracts too fast to pump effectively during ventricular systole, the period when the heart contracts. For out-of-hospital arrests, 75–85% have a primary cardiac cause such as coronary thrombosis; survival rates for out-of-hospital arrests in the developed world are about 8%. Of those persons whose arrest is while they are in hospital, non-cardiac contributory causes include acute respiratory insufficiency, hypotension, severe disturbance of ELECTROLYTES, PULMONARY OEDEMA and PULMONARY EMBOLISM. Irreversible brain damage and death is likely within minutes unless there is prompt treatment. Heart massage, defibrillation and artificial respiration are customary treatment. (See APPENDIX 1: BASIC FIRST AID – Cardiac/respiratory arrest.)