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Asystole Pronunciation: A-sys-tole (ā-ˈsis-tə-lē)

Definition: Asystole is a life-threatening cardiac condition characterized by the absence of electrical activity in the heart, resulting in no heartbeat and a flatline on an ECG.

What is Asystole?


Asystole is a serious form of cardiac arrest where the heart stops beating and no electrical activity is observed on the electrocardiogram (ECG). This condition is typically fatal without immediate treatment, which includes cardiopulmonary resuscitation (CPR) and administration of epinephrine.

Key Facts About Asystole:

  • Asystole is the most severe form of cardiac arrest.
  • The primary treatment for asystole is cardiopulmonary resuscitation (CPR) and administration of epinephrine.
  • Asystole is often an irreversible condition and has a very low survival rate.

Understanding Asystole

Asystole, often referred to as a “flat line,” is a life-threatening cardiac condition characterized by the absence of electrical and mechanical activity in the heart. It’s the most serious form of cardiac arrest and is usually fatal unless treated immediately.

In terms of treatment, basic life support (BLS) in the form of cardiopulmonary resuscitation (CPR) is initiated immediately. Advanced Cardiac Life Support (ACLS) protocols should be followed, including the administration of epinephrine.

`Despite aggressive treatment, the prognosis of asystole is often poor. It is frequently a sign that the patient has reached the terminal phase of a disease, and the survival rate after an episode of asystole is very low.

Frequently Asked Questions About Asystole

What causes asystole?

Asystole, also known as flatline, is a state of no cardiac electrical activity, leading to no cardiac output and cessation of blood flow in the body. It is the most serious form of cardiac arrest and typically has a very poor prognosis. Several conditions can cause asystole, including:

  • Severe cardiac disease: Conditions like coronary artery disease and myocardial infarction can lead to asystole.
  • Hypoxia: Lack of adequate oxygen to the heart can result in asystole.
  • Electrolyte imbalances: Imbalances in potassium and magnesium levels can cause asystole.
  • Drug overdose: Certain drugs, especially those affecting the cardiovascular system, can lead to asystole.
  • Trauma: Trauma to the heart or significant systemic trauma can cause asystole.
  • Acidosis: Severe acidosis can result in asystole.
  • Extreme hypothermia: Extreme lowering of body temperature can cause the heart to stop beating.

How is asystole treated?

The primary treatment for asystole is cardiopulmonary resuscitation (CPR), advanced cardiac life support (ACLS) and administration of vasopressor medications such as epinephrine or vasopressin.

Defibrillation (which is used to deliver shocks in cases of ventricular fibrillation or ventricular tachycardia) is typically not effective for asystole.

Treatment also involves identifying and managing the underlying cause.

This can include administering oxygen, correcting electrolyte imbalances, treating hypothermia, or reversing drug overdoses.

Is asystole reversible?

The reversal of asystole depends largely on the underlying cause and the speed of intervention. If immediate and effective CPR is performed and the underlying cause can be promptly identified and corrected, it may be possible to restore a viable heart rhythm and circulation.

However, asystole is often a terminal rhythm and is associated with a poor prognosis. It’s often a sign that the heart has exhausted its resources and has ceased to function.

Many factors contribute to the potential for reversal, including the patient’s overall health, age, and the duration of the asystole.

It’s worth noting that every minute matters in such cases, as the chance of successful resuscitation decreases rapidly with time.

How CPR Helps During Asystole

CPR (Cardiopulmonary Resuscitation) is directly related to asystole in that it is the primary immediate response to someone experiencing asystole, or a “flatline.” In the absence of a pulse or breathing, the goal of CPR is to artificially circulate oxygenated blood to the body’s vital organs when the heart is unable to do so. This can buy some crucial time while waiting for professional medical assistance or until a defibrillator is available.

When asystole occurs, the heart has stopped beating entirely, and there is no electrical activity within it. Defibrillators, which work by interrupting chaotic rhythm patterns with an electrical shock, are typically ineffective when there is no rhythm to reset. Therefore, the main treatment for asystole is high-quality chest compressions coupled with administering epinephrine, if available, to stimulate the heart.

The key is that CPR must be started quickly and performed effectively. The chest compressions should be at a rate of 100-120 per minute, and about 2 inches deep in adults. This keeps blood circulating, delivering oxygen to the brain and other vital organs. This can prevent or limit damage until the cause of the cardiac arrest can be identified and addressed.

While CPR in response to asystole is a crucial immediate treatment, it’s also important to understand that a patient in asystole will need immediate professional medical care. Asystole is often a terminal event requiring not only resuscitative efforts but also potentially the reversal of the underlying cause, which can range from drug toxicity to severe electrolyte imbalance. Therefore, calling emergency services (like 911 in the United States) is a vital step in the process.


  1. WebMD. (n.d.). Asystole (Flatline): What to Know About Cardiac Arrest. Retrieved from
  2. Cleveland Clinic. (n.d.). Asystole (Flatline). Retrieved from
  3. Healthline. (n.d.). Asystole: Everything You Need to Know. Retrieved from