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 [1] (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.
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. [2]
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. [3] [2]
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. [3]
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 eclectrocardiogram (ECG) test records the heart's electrical activity and will show a flat line if the heart stops beating. [2]
Definition:
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 brain stem 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). [4]
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). [4]
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. [4]
In a study published in the New England Journal of Medicine, 631 subjects' end of life was observed. Of the 631 subjects, 480 subjects were analyzed using a computer program that recorded each subject's vitals in order to monitor for return of pulse or heart activity after at least 1 minute of flatlining. The study found that 14% of subjects had a return of heart activity but none regained consciousness. [5] 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. [6]
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. [7]
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. [8] This sparked research into modern ECG technology, which was developed from the mercury capillary electrometer by Willem Einthoven. In 1901 to 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. [9] This led to Einthoven's Nobel Prize in 1924. [10] [8] With the ECG, the characteristics of a dying heart were identified, creating the leading tool for diagnosing death– even to this day. [7]
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. [7] 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. [11] The machine consisted of steel electrodes that get mounted on the scalp with an EEG cap to visualize and interpret signals. [12] He noted that the human brain has a specific pattern, called alpha oscillations, and went on to publish this in 1929. [13] 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. [12] They determined that a person reached this state when they were apneic, comatose, without brainstem reflexes, and showed no electroencephalographic (EEG) activity. [12]
When an individual experiences asystole or cardiac flatline, there is no electrical activity in their heart which is evidenced by the flatline recorded by an ECG. [2] 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 [14] 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. [16]
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 [4] available to them:
Bradycardia is a medical term used to describe a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from a variety of pathologic processes, it is commonly a physiologic response to cardiovascular conditioning, or due to asymptomatic type 1 atrioventricular block. Resting heart rates less than 50 BPM are often normal during sleep in young and healthy adults, and in athletes. In large population studies of adults without underlying heart disease, resting heart rates of 45-50 BPM appear to be the lower limits of normal, dependent on age and sex. Bradycardia is most likely to be discovered in the elderly, as both age and underlying cardiac disease progression contribute to its development.
The diagnostic tests in cardiology are methods of identifying heart conditions associated with healthy vs. unhealthy, pathologic heart function.
Cardiac arrest, also known as sudden cardiac arrest, is when the heart suddenly and unexpectedly stops beating. As a result blood will not be pumped around the body in normal circulation, consciousness will be rapidly lost, and breathing will be abnormal or absent. Without immediate intervention such as cardiopulmonary resuscitation (CPR), and possibly defibrillation, death will occur within minutes.
Electrocardiography is the process of producing an electrocardiogram, a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including cardiac rhythm disturbances, inadequate coronary artery blood flow, and electrolyte disturbances.
Defibrillation is a treatment for life-threatening cardiac arrhythmias, specifically ventricular fibrillation (V-Fib) and non-perfusing ventricular tachycardia (V-Tach). A defibrillator delivers a dose of electric current to the heart. Although not fully understood, this process depolarizes a large amount of the heart muscle, ending the arrhythmia. Subsequently, the body's natural pacemaker in the sinoatrial node of the heart is able to re-establish normal sinus rhythm. A heart which is in asystole (flatline) cannot be restarted by a defibrillator; it would be treated only by cardiopulmonary resuscitation (CPR) and medication, and then by cardioversion or defibrillation if it converts into a shockable rhythm.
Ventricular fibrillation is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by sudden cardiac death in the absence of treatment. Ventricular fibrillation is initially found in about 10% of people with cardiac arrest.
Brain death is the permanent, irreversible, and complete loss of brain function which may include cessation of involuntary activity necessary to sustain life. It differs from persistent vegetative state, in which the person is alive and some autonomic functions remain. It is also distinct from comas as long as some brain and bodily activity and function remain, and it is also not the same as the condition locked-in syndrome. A differential diagnosis can medically distinguish these differing conditions.
Asystole is the absence of ventricular contractions in the context of a lethal heart arrhythmia. Asystole is the most serious form of cardiac arrest and is usually irreversible. Also referred to as cardiac flatline, asystole is the state of total cessation of electrical activity from the heart, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.
Willem Einthoven was a Dutch medical doctor and physiologist. He invented the first practical electrocardiograph in 1895 and received the Nobel Prize in Physiology or Medicine in 1924 for it.
Hypermagnesemia is an electrolyte disorder in which there is a high level of magnesium in the blood. Symptoms include weakness, confusion, decreased breathing rate, and decreased reflexes. Complications may include low blood pressure and cardiac arrest.
Pulseless electrical activity (PEA) is a form of cardiac arrest in which the electrocardiogram shows a heart rhythm that should produce a pulse, but does not. Pulseless electrical activity is found initially in about 20% of out-of-hospital cardiac arrests and about 50% of in-hospital cardiac arrests.
Deep hypothermic circulatory arrest (DHCA) is a surgical technique in which the temperature of the body falls significantly and blood circulation is stopped for up to one hour. It is used when blood circulation to the brain must be stopped because of delicate surgery within the brain, or because of surgery on large blood vessels that lead to or from the brain. DHCA is used to provide a better visual field during surgery due to the cessation of blood flow. DHCA is a form of carefully managed clinical death in which heartbeat and all brain activity cease.
A Bioamplifier is an electrophysiological device, a variation of the instrumentation amplifier, used to gather and increase the signal integrity of physiologic electrical activity for output to various sources. It may be an independent unit, or integrated into the electrodes.
The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.
Syncope, commonly known as fainting, or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from low blood pressure. There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm. Syncope may also be associated with a short episode of muscle twitching. Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event, usually medical in nature. When consciousness and muscle strength are not completely lost, it is called presyncope. It is recommended that presyncope be treated the same as syncope.
Flatline may mean:
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Some types of arrhythmias have no symptoms. Symptoms, when present, may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath, chest pain, or decreased level of consciousness. While most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.
Clinical Electrophysiological Testing is based on techniques derived from electrophysiology used for the clinical diagnosis of patients. There are many processes that occur in the body which produce electrical signals that can be detected. Depending on the location and the source of these signals, distinct methods and techniques have been developed to properly target them.
Ictal bradycardia is when people with temporal lobe epilepsy experience bradycardia with their seizures. Bradycardia is defined by a slower than normal heart rate, less than 60 bpm..
An electrogram (EGM) is a recording of electrical activity of organs such as the brain and heart, measured by monitoring changes in electric potential.