thumb|Flatlined [[Electrocardiogram|ECG lead]]
A flatline is an electrical time sequence measurement that shows no activity and therefore, when represented, shows a flat line instead of a moving one. It almost always refers to either a flatlined electrocardiogram, where the heart shows no electrical activity (asystole), or to a flat electroencephalogram, in which the brain shows no electrical activity (brain death). Both of these specific cases are involved in various definitions of death.
ECG/EKG (Electrocardiogram/Cardiac) flatline
A cardiac flatline is also called asystole. It can possibly be generated by malfunction of the electrocardiography device, but it is recommended to first rule out true asystole because of the emergence of such condition.
Definition:
A cardiac flatline is referred to as asystole. It can be identified by using an ECG/EKG (electrocardiogram) test. Asystole occurs when the electrical and mechanical activities of the heart stop.
The electroencephalogram (EEG) records the brain's electrical activity and will show a flat line if the brain is dead. Neuro flatline or brain death happens after cardiac arrest or cardiac flatline. It can take 2 to 20 seconds after cardiac flatline for the brain to show no activity.
History
The definition of death has changed over time, but the loss of cardiac and neurological function have been the main criteria for centuries. The concept of flatlining begins to take form with the invention of technologies for death determination.
It began in 1837 when Professor Manni at the University of Rome offered a cash prize to the doctor who could offer a true test of death. The winner, Dr. Eugene Bouchut used new technology– the stethoscope– to determine death when heart sounds were absent for over two minutes. In 1883 he updated his criteria to require five minutes without heart sounds to qualify cardiac death.
Then, the standard for viewing cardiac activity changed in 1887 when Augustus Waller recorded the first ECG from the human heart with a mercury capillary electrometer. This sparked research into modern ECG technology, which was developed from the mercury capillary electrometer by Willem Einthoven. Between 1901 and 1905, Einthoven developed the string galvanometer, which could measure and record the heart's electrical activity. Electrodes were place on three points, the "Einthoven leads", the right and left arms and on the left foot same as today and provided precise recordings of the heart. This led to Einthoven's Nobel Prize in 1924. The machine consisted of steel electrodes that get mounted on the scalp with an EEG cap to visualize and interpret signals. The presence of this technology along with resuscitation technology saw the use of the EEG to determine a time in which the person had reached total death. In 1959, this concept—brain death—was first coined as by Mollaret and Goulon. They determined that a person reached this state when they were apneic, comatose, without brainstem reflexes, and showed no electroencephalographic (EEG) activity. The lack of electrical activity also means that the individual's heart will stop pumping. Following a cardiac flatline a fast intervention is a priority and can affect individual outcomes and recovery.
Treatment for cardiac flatline or asystole can involve:
- CPR (cardiopulmonary resuscitation)
- Administering a vasopressin such as epinephrine
- Trying to identify what could be causing the cardiac flatline in the first place.
Treatment decisions will depend on where an individual is when they go into asystole. When an individual goes into cardiac arrest providers will start CPR immediately and then try to determine whether the rhythm is shockable. While defibrillation is often portrayed as a common treatment option in popular media, since asystole is an unshockable rhythm defibrillation is not a recommended course of treatment. Successful resuscitation is generally unlikely and is inversely related to the length of time spent attempting resuscitation.
Following a treatment intervention, the individuals who survive may still suffer long-term consequences of their cardiac flatline.
Brain death (neurological flatline)
An individual's cardiac flatline can progress to neurological flatline, which is also referred to as brain death. After an individual's heart stops beating, if providers are unable to successfully intervene within the window, the individual's brain cells will die from this lack of blood and oxygen and this damage is irreversible and permanent. The criteria to diagnose brain death has been outlined in the above sections of this article. While brain death cannot be treated, individuals and their families have several options