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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 (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 he ...
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 possi ...
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 (biology), 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 ca ...
, 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 n ...
, 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 ''coun ...
) 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 intensi ...
, with the rate being lower (6%) for those already prescribed drugs for high blood pressure. 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 An antihypotensive agent, also known as a vasopressor agent or simply vasopressor, or pressor, is any substance, whether endogenous or a medication, that tends to raise low blood pressure. Some antihypotensive drugs act as vasoconstrictors to i ...
such as epinephrine (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 abnorm ...
). 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 ...
—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'' describe ...
) * Hypothermia * Hyperkalemia or Hypokalemia * Toxins (e.g.,
drug overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended.
) * 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 ma ...
or pulmonary embolism) 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 spont ...
or internal cardiac massage (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. 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 brain damage, resulting in brain death or persistent vegetative state. Image:Lead II rhythm generated asystole.JPG, ECG lead showing asystole (flatline) File:Asystole.png, Asystole File:Asystole Coarse.png, Ventricular Fibrillation


See also

*
Agonal heart rhythm In medicine, an agonal heart rhythm is a variant of asystole. Agonal heart rhythm is usually ventricular in origin. Occasional P waves and QRS complexes can be seen on the electrocardiogram. The complexes tend to be wide and bizarre in morphol ...
*
Ictal asystole Ictal asystole is a rare occurrence for patients that have temporal lobe epilepsy. It can often be identified by loss of muscle tone or the presence of bilateral asymmetric jerky limb movements during a seizure, although ECG Electrocardiograph ...


References


External links

{{Heart diseases Medical aspects of death Medical emergencies Causes of death Cardiac arrhythmia