Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain life. It occurs when the heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 stops beating in a regular rhythm, a condition called cardiac arrest

Cardiac arrest

Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...

. The term is also sometimes used in resuscitation research.

Stopped blood circulation has historically proven irreversible in most cases. Prior to the invention of cardiopulmonary resuscitation

Cardiopulmonary resuscitation

Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

 (CPR), defibrillation

Defibrillation

Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...

, epinephrine

Epinephrine

Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

 injection, and other treatments in the 20th century, the absence of blood circulation (and vital functions related to blood circulation) was historically considered to be the official definition of death

Death

Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

.