What Is Asystole?

Medically Reviewed by James Beckerman, MD, FACC on February 04, 2022
3 min read

Asystole (ay-sis-stuh-lee) is when there’s no electricity or movement in your heart. That means you don’t have a heartbeat. It’s also known as flatline. That’s because doctors check the rhythm of your heart with a machine called an electrocardiogram -- also called an ECG or EKG. It shows a straight line when there’s no heartbeat.

Asystole happens to everyone when they die. But some conditions raise your chances of it happening early. One of them is certain types of arrhythmia, or irregular heartbeat. A heart injury or genetics -- something that runs in your family -- could also lead to asystole.

If you’re worried about your heart, talk to your doctor. They’ll let you know if something’s going on and what you need to do.

An electrical signal triggers your heart’s two upper chambers, or atria. This pulse travels down to the two lower chambers, or ventricles. It tells your atria to fill with and release blood. Then the ventricles pump it out. Normally, this happens about 60-100 times a minute. That’s your heartbeat.

Asystole is caused by a glitch in your heart’s electrical system. You can get a ventricular arrhythmia when the signals are off. That’s when your lower chambers don’t beat the right way. So your heart can’t pump blood to the rest of your body. This is cardiac arrest. Ventricular arrhythmias that may lead to asystole are:

Ventricular fibrillation. With VFib, the lower chambers tremble, or fibrillate, instead of contracting normally. If it’s not treated within a few minutes, you can die. Your chances of VFib are higher if you:

  • Have a weak heart muscle (cardiomyopathy)
  • Have already had a heart attack
  • Have heart disease
  • Are born with certain genetic diseases (long or short QT syndrome, Brugada syndrome)
  • Take medications that affect your heart
  • Have an electrolyte imbalance
  • Have drug poisoning
  • Have a serious infection (sepsis)

Pulseless ventricular tachycardia. Your heart will beat so fast, it can’t pump blood. V-tach can be life-threatening if it lasts for more than a few seconds. It may turn into VFib. Your chances of V-tach are higher if you:

  • Have a weak heart muscle (cardiomyopathy)
  • Have had a heart attack before
  • Use illegal drugs, like cocaine
  • Take certain medications
  • Have sarcoidosis (an inflammatory disease)

Pulseless electrical activity (PEA). This is when you have electricity in your heart, but it doesn’t pump normally. It can turn into asystole if not treated right away.

Other conditions that may lead to asystole include:

  • Hypoxia: Low oxygen
  • Hypovolemia: Low levels of blood in your body
  • Hypo/hyperkalemia: Too little or too much potassium
  • Hypothermia: Body temperature that’s too low
  • Hydrogen ion (acidosis): Too much acid in the body
  • Tension pneumothorax: Air pressure buildup around your lungs
  • Tamponade: Blood or fluid buildup around your heart
  • Toxins: Poisons in your body
  • Thrombosis:Blood clots in your heart or lungs

These should also be treated right away.

In the movies, they sometimes shock a flatlined heart with a defibrillator. That’s a machine that uses an electric pulse to get your heartbeat back to normal. But it doesn’t usually help in real life. Typically, less than 2% of people survive asystole. Your odds depend on what causes your heart to stop. If you can be treated, a doctor or paramedic may give you:

  • Cardiopulmonary resuscitation (CPR). High-quality CPR acts like a heartbeat. This can keep blood flowing through your body.
  • Epinephrine. Also called adrenaline, this drug can boost blood flow. Some experts think more research is needed on its role in cardiac arrest.

Someone in cardiac arrest might:

Call 911 right away if you think someone is in cardiac arrest. If you know how, give them hands-only CPR until emergency workers arrive. It’s a good idea to wear a medical ID bracelet if you have a heart problem.