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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.
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.
Causes:
ECG/EKG flatline or asystole occurs when the heart's electrical and mechanical activities stop. It also results from other causes such as hypoxia, acidosis, hypokalemia, hyperkalemia, hypovolemia, toxins, pulmonary thrombosis, and coronary thrombosis. Additional causes could also include tension pneumothorax and cardiac tamponade. These conditions should be treated immediately when identified.
ECG flat line also occurs when the electrocardiographic (ECG/EKG) leads or recording electrodes are placed incorrectly. It can be caused by malfunction of the electrocardiogram (ECG/EKG) machine.
Diagnosis:
ECG flatline or asystole is diagnosed when a person, who is in cardiac arrest (the heart stops beating), is experiencing the following conditions:
The electrocardiogram (ECG) test records the heart's electrical activity and will show a flat line if the heart stops beating.
A neurological flatline is referred to as brain death. It can be identified by using an EEG (electroencephalogram) test. Brain death is the loss of function of the brain, the cerebrum, that is responsible for thinking and the deep brain or the Brainstem that is responsible for the breathing and reflexes such as pupillary light reflex (the constriction of the pupil of the eye in response to light) and gag reflex or pharyngeal reflex (contraction of pharyngeal muscle).
Causes:
EEG flat line or brain death can result from a head injury that leads to brain damage and bleeding. Brain death also results from a lack of blood flow to the brain because the heart stops beating (cardiac arrest), which is when the ECG imaging shows a cardiac flat line (asystole).
Diagnosis:
Brain death is diagnosed if a person is experiencing all of the following three conditions:
The electroencephalogram (EEG) records the brain's electrical activity and will show a flat line if the brain is dead.
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. With the ECG, the characteristics of a dying heart were identified, creating the leading tool for diagnosing death—even to this day.
However, in the mid 19th century with the invention of the defibrillator and cardioversion, it was realized that the flatline on the ECG did not always mean death. This instigated research into other ways to determine death, which eventually lead to the idea of brain death.
In 1924, a German physiologist and psychiatrist Hans Berger recorded the first EEG on a human brain. The machine consisted of steel electrodes that get mounted on the scalp with an EEG cap to visualize and interpret signals. He noted that the human brain has a specific pattern, called alpha oscillations, and went on to publish this in 1929. 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 le coma dépassé 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.
Treatment for cardiac flatline or asystole can involve:
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.
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