Sudden cardiac arrest (SCA) for tachycardia

  • ~ 475,000 Americans die from cardiac arrest each year.1
  • ICDs are 98% effective in treating dangerous ventricular arrhythmias.2,3

What is SCA?

SCA is an electrical problem with the heart that triggers a dangerously fast heart rate (ventricular tachycardia) or irregular rhythm (ventricular fibrillation). If not treated immediately, SCA can be fatal. Approximately 95% of people who experience an out-of-hospital cardiac arrest event and are not treated by defibrillation within 10 minutes will die.1

SCA versus heart attack

SCA is not the same as a heart attack.

Think of your house: It needs plumbing and electricity to work as it should — and it has the potential for both plumbing and electrical problems. The same can happen with your heart. A heart attack is primarily a plumbing (blood flow) problem; SCA is an electrical (heart rhythm) problem.

Illustration of home with numbers for blue electric line and pink water pipe plumbing below the house

1. SCA is an electrical issue.

SCA is a rhythm problem that prevents the heart from pumping blood to the brain and organs.

2. A heart attack is a plumbing issue.

A heart attack is typically caused by a blockage in a blood vessel to the heart muscle. This can permanently damage part of the heart and can lead to cardiac arrest.

Immediate action saves lives.

Survival rates can double or triple if more people take action and know how to respond in the case of an SCA1:

1. Call emergency hotline.

2. Administer CPR.

3. If available, use an automated external defibrillator (AED) to provide an electronic shock to the heart within minutes.

What are the symptoms of SCA?

  • Dizziness
  • Fast heartbeat
  • Loss of consciousness

What are the risk factors for SCA?

  • Previous heart attack or SCA
  • Family history of SCA or other heart disease
  • Heart failure
  • Low ejection fraction
  • Rapid or abnormal heartbeats starting in the lower chambers of the heart

Do you know your ejection fraction (EF)?

Why is knowing your EF important?

EF is a measurement of the percentage of blood pumped (or ejected) from the left ventricle in your heart with each beat. Understanding how well your blood is pumping can help your doctor diagnose and track heart failure and determine the right course of treatment for you.

If you are someone with a heart condition, it's important to know your EF. Ask your physician about your EF.

What does this measurement mean?

  • 50–75%: Heart's pumping ability is normal.4
  • 36–49%: Heart's pumping ability is below normal.4
  • 35% and below: Heart's pumping ability is low.4

Treating SCA through defibrillation

The most effective way to treat SCA is through defibrillation. It involves delivering an electrical shock to your heart to restore the normal heartbeat. There are two types of devices that can deliver these electrical shocks: Automated external defibrillators (AEDs) and ICDs.
Blue illustration of an automated external defibrillator (AED)


An AED is a portable device used by emergency response teams or the general public to shock the heart — giving the heart a chance to restart normal electrical activity and resume beating effectively. 

Pacemaker Icon


An ICD is likely to be recommended for long-term treatment of irregular rhythms and prevention of SCA. The small, battery-powered device is surgically placed below the collarbone. One or more thin wires (leads) from the ICD run through the veins to the heart. The device constantly monitors the heart's rhythm so it can regulate the heart rate if it detects an irregular rhythm. It can send either high-energy shocks or low-energy, painless pacing stimulation to disrupt a dangerously fast heart rhythm.5

Ask the ICD.

Visit Ask the ICD, an interactive website full of questions and answers about living with an ICD.



CPR Facts & Stats. American Heart Association. Available at: Accessed September 19, 2022.


Zipes DP, Roberts D. Results of the international study of the implantable pacemaker cardioverter-defibrillator. A comparison of epicardial and endocardial lead systems. The Pacemaker-Cardioverter-Defibrillator Investigators. Circulation. July 1995;92(1):59-65. 


Volosin KJ, et al. Virtual ICD: A Model to Evaluate Shock Reduction Strategies. Presented at HRS 2010 (PO3-125). 


Solomon SD, Anavekar N, Skali H, et al. Influence of ejection fraction on cardiovascular outcomes in a broad spectrum of heart failure patients. Circulation. December 13, 2005;112(24):3738-3744.


Sudden cardiac arrest. Mayo Clinic. Available at: Accessed September 19, 2022.