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Asystole - Causes and Prevention

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The flat line that we see in the electrocardiogram indicates the absence of a heartbeat and is medically termed asystole. Scroll through the article below to know more.

Medically reviewed by

Dr. Sapkal Ganeshrao Patilba

Published At April 11, 2022
Reviewed AtDecember 29, 2023


Asystole happens when there is no movement or electrical activity in the heart, meaning there is no heartbeat. It is also called a flat line (as it appears as a flat line in the machine). In contrast, systole and diastole indicate the movement of the heart in terms of contraction and relaxation of the cardiac muscle.

The doctors check the rhythm of the heart with the help of a machine called an electrocardiogram, which is also known as ECG or EKG. This machine is used to check the heartbeat, and it shows as a straight line when the person does not have a heartbeat.

Even though asystole is common to occur in older people, in some conditions, it may occur during the early periods of life. Irregular heartbeat, heart injury, and certain types of arrhythmia are a few conditions that may lead to asystole in the early periods of life. Also, the genes that run in the families could lead to asystole.

How Does Our Heart Work?

The heart is a muscular organ situated between the two lungs in the mediastinum. It pumps blood throughout the body and is made up of four chambers. An electrical signal triggers the two upper chambers or atria of the heart.

This signal travels down to the two lower chambers (ventricles). This transmission of signals helps the atria to fill and release the blood so that the ventricles pump it out. Usually, this cycle happens 60 times to 100 times a minute, which is the heartbeat. This cardiac cycle is repeated during every heartbeat as a sequence of coordinated events in a cyclic manner.

What Causes Asystole?

The absence of a heartbeat occurs when there is a minor malfunction in the heart’s electrical system. A ventricular arrhythmia happens when the signals get cut off due to some glitch in the electrical system; hence the lower chambers will not be able to beat the right way. This makes the heart unable to pump blood to the rest of the body, resulting in cardiac arrest. Ventricular arrhythmias that lead to the absence of a heartbeat are:

a. Ventricular Fibrillation - In the case of ventricular fibrillation, the lower chambers find it difficult to do their normal activity, that is, the normal ventricular contraction; instead, they start to fibrillate. It should be treated as soon as possible within minutes, or else it may result in death. People are more susceptible to getting ventricular fibrillation if they have the below conditions:

  • Having a weak heart muscle, medically known as cardiomyopathy.

  • If they have already experienced a heart attack.

  • Any heart disease.

  • Congenital genetic diseases such as Brugada syndrome and long or short QT syndrome.

  • People under medication for heart diseases.

  • Electrolyte imbalance.

  • Drug poisoning or drug overdose.

  • Serious infection or sepsis.

b. Pulseless Ventricular Tachycardia - The heart will beat so fast, but it cannot pump blood. Ventricular tachycardia can be a life-threatening condition when it lasts for more than a few seconds because it may turn into ventricular fibrillation. People are more susceptible to getting ventricular tachycardia if they have the following:

  • A weak heart muscle is also known as cardiomyopathy.

  • A previous heart attack.

  • Usage of illegal drugs, like Cocaine.

  • Under certain medications.

  • Have an inflammatory disease, such as sarcoidosis.

c. Pulseless Electrical Activity (PEA) - When the heart has its electrical activity but is unable to pump normally, it is known as pulseless electrical activity. When it is not treated the right way, it may turn into asystole. Some of the other conditions that may result in the absence of the heartbeat when not treated the right way are:

  • Hypoxia (low oxygen).

  • Hypovolemia (decreased blood levels in the body).

  • Hypo or hyperkalemia (decrease or increase in potassium levels).

  • Hypothermia (decrease in the body temperature).

  • Increase in the hydrogen ion concentration (metabolic acidosis).

  • Tension pneumothorax (buildup of air in the lungs).

  • Tamponade (blood or fluid buildup in the heart).

  • Toxins or poisons in the body.

  • Thrombosis (blood clots that obstruct the blood flow to the heart or lungs).

How Can Asystole Be Prevented?

Get a timely medical check-up as it helps the doctor to check you for heart problems, such as arrhythmia. Before it gets worse, the doctor may find ways to fix the heartbeat if it is irregular. You may be suggested the following treatments to avoid complications. They are:

  • Doctor prescribed medications.

  • Following healthy lifestyle changes.

  • An implantable cardioverter defibrillator.

  • Undergoing surgery.

Can Asystole Be Reversed?

We have mostly come across shocking a flatlining heart with a defibrillator in the movies. It is a machine that uses an electric pulse to bring back the heartbeat to normal. But it usually does not help in real life. Only less than 2 % of people survive asystole, but it also depends on the causes that made your heart stop. When it is a treatable cause, the doctor or paramedic may give you the following.

  • Cardiopulmonary Resuscitation (CPR) - It is the mainstay treatment and helps to make the blood flow through the body. A high-quality cardiopulmonary resuscitation (CPR) should be done in less than 5 seconds with minimal intervention, and it acts as a heartbeat.

  • Epinephrine - It is also known as Adrenaline and is given 1 mg via intravenous or intraosseous line as this drug helps to boost blood flow within the body, but its role in treating cardiac arrest is under study.


Asystole is a life-threatening condition, and attempts to save the affected one’s life are almost impossible. But this does not stop professionals from offering lifesaving medical help. A meager percentage of people being saved from asystole does exist. Call 911 or your local emergency helpline in case of chest pain or cardiac conditions. Every second counts!

Frequently Asked Questions


Does Asystole Mean Death?

A specific type of cardiac arrest called asystole occurs when the heart completely stops beating. Without prompt CPR or medical attention, this situation is fatal in a matter of minutes.


Why Isn’t Asystole Shockable?

It is known as a non-shockable rhythm because an asystole rhythm indicates that the heart's electrical system has stopped and there is no heartbeat. Therefore, defibrillation is not performed during an asystole.


Can You Bring Someone Back From Asystole?

There may yet be a chance to revive someone because the brain cells can endure a lack of blood flow for around five minutes. There is a small chance that they will survive if medical personnel can restart their heart immediately.


What Is the Survival Rate of Asystole?

According to reports, just 2% of asystole patients survive.


Can CPR Restart a Stopped Heart?

In cases of sudden cardiac arrest, cardiopulmonary resuscitation (CPR) cannot restart the heart. CPR is only a temporary measure used to maintain a minimum oxygen supply to the brain and other organs. Defibrillation is the only procedure that can restore a regular heartbeat in a person experiencing sudden cardiac arrest. However, in asystole, only CPR is effective and not defibrillation.


Why Do Doctors Hit the Chest Before CPR?

The procedure where doctors hit the chest is referred to as a precordial thump. Only when applied quickly, just before the development of ventricular fibrillation or pulseless ventricular tachycardia, can precordial thump be beneficial. The precordial thump seeks to stabilize the patient's ventricular tachycardia and shift their rhythm to one that is more stable and organized.


Does Asystole Mean No Pulse?

No pulse and no electrical activity in asystole.


What Is the First Drug for Asystole?

Epinephrine, atropine, and calcium chloride are the standard medications used to treat asystole during cardiac arrest.


What Are Two Treatments for Asystole?

- Cardiopulmonary resuscitation (CPR) 
- Epinephrine


How Do You Confirm Asystole?

Cardiovascular monitoring detects asystole. The cardiac monitor displays an isoelectric "flat" line during asystole instead of a waveform.
Dr. Sapkal Ganeshrao Patilba
Dr. Sapkal Ganeshrao Patilba



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