Asystole (New Latin, from Greek
privative a "not, without" + ''systolē'' "contraction") is the absence of ventricular contractions in the context of a lethal
heart arrhythmia
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 adult ...
(in contrast to an induced asystole on a cooled patient on a
heart-lung machine
Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and oxygen to the body. The CPB pump itself is often referred to as a ...
and
general anesthesia
General anaesthesia (UK) or general anesthesia (US) is a medically induced loss of consciousness that renders the patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general ...
during surgery necessitating stopping the heart). Asystole is the most serious form of
cardiac arrest
Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possib ...
and is usually irreversible. Also referred to as cardiac flatline, asystole is the state of total cessation of electrical activity from the
heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...
, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.
Asystole should not be confused with very brief pauses in the heart's electrical activity—even those that produce a temporary flatline—that can occur in certain less severe abnormal rhythms. Asystole is different from very fine occurrences of
ventricular fibrillation
Ventricular fibrillation (V-fib or VF) 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 p ...
, though both have a poor prognosis, and untreated fine VF will lead to asystole. Faulty wiring, disconnection of electrodes and leads, and power disruptions should be ruled out.
Asystolic patients (as opposed to those with a "shockable rhythm" such as coarse or fine ventricular fibrillation, or unstable
ventricular tachycardia
Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...
that is not producing a pulse, which can potentially be treated with
defibrillation
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 (often called a ''cou ...
) usually present with a very poor prognosis. Asystole is found initially in only about 28% of cardiac arrest cases in hospitalized patients,
but only 15% of these survive, even with the benefit of an
intensive care unit
220px, Intensive care unit
An intensive care unit (ICU), also known as an intensive therapy unit or intensive treatment unit (ITU) or critical care unit (CCU), is a special department of a hospital or health care facility that provides intensiv ...
, with the rate being lower (6%) for those already prescribed drugs for
high blood pressure
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
.
Asystole is treated by
cardiopulmonary resuscitation
Cardiopulmonary resuscitation (CPR) is an emergency procedure consisting of chest compressions often combined with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore spont ...
(CPR) combined with an intravenous
vasopressor such as
epinephrine
Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
(a.k.a. adrenaline). Sometimes an underlying reversible cause can be detected and treated (the so-called "
Hs and Ts", an example of which is
hypokalaemia
Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an abnor ...
). Several interventions previously recommended—such as defibrillation (known to be ineffective on asystole, but previously performed in case the rhythm was actually very fine ventricular fibrillation) and intravenous
atropine
Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate, and to decrease saliva production during surgery. It is typically given i ...
—are no longer part of the routine protocols recommended by most major international bodies. 1 mg epinephrine by IV every 3–5 minutes is given for asystole.
Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation; asystole is itself not a "shockable" rhythm. Even in those cases where an individual suffers a cardiac arrest with asystole and it is converted to a less severe shockable rhythm (ventricular fibrillation, or ventricular tachycardia), this does not necessarily improve the person's chances of survival to discharge from the hospital, though if the case was witnessed by a civilian, or better, a paramedic, who gave good CPR and cardiac drugs, this is an important confounding factor to be considered in certain select cases. Out-of-hospital survival rates (even with emergency intervention) are less than 2 percent.
Cause
Possible underlying causes, which may be treatable and reversible in certain cases, include the
Hs and Ts.
*
Hypovolemia
*
Hypoxia
*
Hydrogen ions (
acidosis
Acidosis is a process causing increased acidity in the blood and other body tissues (i.e., an increase in hydrogen ion concentration). If not further qualified, it usually refers to acidity of the blood plasma.
The term ''acidemia'' describes ...
)
*
Hypothermia
*
Hyperkalemia or
Hypokalemia
*
Toxins (e.g.,
drug overdose)
*
Cardiac Tamponade
*
Tension pneumothorax
*
Thrombosis (
myocardial infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...
or
pulmonary embolism
Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain p ...
)
While the heart is asystolic, there is no blood flow to the brain unless
CPR
Cardiopulmonary resuscitation (CPR) is an emergency procedure consisting of chest compressions often combined with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore sponta ...
or
internal cardiac massage
Cardiopulmonary resuscitation (CPR) is an emergency procedure consisting of chest compressions often combined with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore sponta ...
(when the chest is opened and the heart is manually compressed) is performed, and even then it is a small amount. After many emergency treatments have been applied but the heart is still unresponsive, it is time to consider pronouncing the patient
dead
Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
. Even in the rare case that a rhythm reappears, if asystole has persisted for fifteen minutes or more, the brain will have been deprived of oxygen long enough to cause severe
hypoxic
Hypoxia means a lower than normal level of oxygen, and may refer to:
Reduced or insufficient oxygen
* Hypoxia (environmental), abnormally low oxygen content of the specific environment
* Hypoxia (medical), abnormally low level of oxygen in the t ...
brain damage
Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating t ...
, resulting in
brain death or
persistent vegetative state
A persistent vegetative state (PVS) or post-coma unresponsiveness (PCU) is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. After four weeks in a vegetative stat ...
.
See also
*
Agonal heart rhythm
*
Ictal asystole
References
External links
{{Heart diseases
Medical aspects of death
Medical emergencies
Causes of death
Cardiac arrhythmia