How to Recognize Sudden Cardiac Arrest and Act Fast

When someone collapses, stops breathing, and becomes unresponsive, your ability to recognize sudden cardiac arrest and respond quickly can mean the difference between life and death. It’s one of the most serious medical emergencies, and it often strikes without warning, even in otherwise healthy individuals. Whether you’re at home, at work, or in a public place, knowing what to look for — and what to do — can dramatically improve a person’s chance of survival.

What is sudden cardiac arrest?

Sudden cardiac arrest (SCA) occurs when the heart’s electrical system malfunctions, causing the heart to stop beating properly. This electrical problem can trigger abnormal heart rhythms, like ventricular fibrillation, which prevents the heart muscle from pumping enough blood to the vital organs.

Without this oxygen-rich blood, the brain and body quickly begin to shut down. Within minutes, permanent brain damage or death can occur if no action is taken.

It's important to understand that SCA is not the same as a heart attack. A heart attack happens when a blocked artery cuts off blood flow to a part of the heart, typically due to coronary artery disease or a blood clot. But SCA is an electrical malfunction that leads to the unexpected loss of heart function, often without any prior symptoms.

Who is at risk for sudden cardiac arrest?

Sudden cardiac arrest is one of the leading causes of death in the United States, affecting nearly 1,000 people a day. According to the Sudden Cardiac Arrest Foundation, there are more than 356,000 out-of-hospital cardiac arrests (OHCA) each year, with nearly 90% being fatal. However, survivors of cardiac arrest often experience complications, such as impaired consciousness and cognitive deficits, often resulting in reduced quality of life and shortened life span. Therefore, early CPR and AED use are the key to increasing the chances of survival and recovery.

While SCA can affect anyone, certain groups of people (e.g., older adults and males) are at greater risk for cardiac arrest. Sudden cardiac arrest risk factors mimic those of heart disease, including a family history of coronary heart disease, smoking, high blood pressure, high blood cholesterol, obesity, diabetes and a sedentary lifestyle. Other risk factor might include:

• A personal or family history of heart problems, such as heart attack, heart failure, irregular heart rhythm, or known or undiagnosed congenital heart conditions.
• Substance use or drug overdose.
• Low potassium or magnesium levels.
• Obstructive sleep apnea.
• Chronic kidney disease.

Because sudden cardiac arrest can happen to anyone, raising awareness, encouraging regular health screenings, and expanding access to CPR and AED training are essential steps to improving survival rates.

What sudden cardiac arrest looks like

The most telling indicator of SCA is a sudden collapse. A person experiencing sudden cardiac arrest will often drop to the ground without warning, lose consciousness, and stop responding. In many cases, normal breathing stops almost immediately.

Some individuals may show seizure-like activity — typically lasting 10 to 20 seconds — as the brain begins to shut down due to lack of oxygen.

After collapse, the person may exhibit abnormal gasping, known as agonal breathing. These irregular breaths can last for several minutes but are not signs of life. Agonal gasps may sound like snorting, gurgling, or labored breathing. It's critical that bystanders do not mistake this for normal breathing as immediate action is still needed.

What to do: Responding in those first critical moments

If someone is experiencing sudden cardiac arrest, there’s no time to wait. Quick response times can mean the difference not only between life and death, but also between full recovery and lasting complications.

CPR is the immediate treatment for suspected sudden cardiac arrest. However, CPR alone isn’t enough. Follow these steps:

1. Call 911. Start by activating emergency services. The faster medical help is on the way, the higher the chances of survival. Send someone to get the first aid kit and an on-site automated external defibrillator (AED).
2. Begin chest compressions. If the person is unresponsive and not breathing normally, begin chest compressions. Push hard and fast in the center of the chest, at a rate of 100 to 120 beats per minute. Chest compressions help move oxygen-rich blood to the brain and vital organs, buying time until defibrillation or advanced care is available. If you’ve never taken a CPR class, hands-only CPR is easy to learn and effective.
3. Use an AED as soon as it’s available. Turn it on and follow the voice prompts. AEDs are designed to assess the heart’s rhythm and deliver an electric shock if needed to correct pulseless ventricular tachycardia and ventricular fibrillation. Using an AED within the first several minutes of collapse can significantly increase outcomes. That’s why the presence of AEDs in public spaces, such as schools, gyms, offices, and community centers, can make all the difference.

Your willingness to act in those first few minutes can give someone their best chance of survival and recovery.

Why CPR, AED, and First Aid training matters

Despite how common and deadly sudden cardiac arrest is, bystander intervention remains alarmingly low. Fewer than half of OHCA victims receive bystander CPR, and AEDs are used in only a small fraction of cases. Yet, these simple actions can dramatically increase a person’s chance of survival and reduce the risk of permanent brain damage or other impairments.

Training in CPR, AED, and First Aid equips individuals with the skills and confidence to respond effectively to SCA and other medical emergencies. High-quality training allows for:

• Hands-on, scenario-based learning. Engage in realistic simulations that mirror real-life emergencies, enhancing retention and readiness.
• Instructor-led sessions with real-time feedback. Benefit from immediate guidance to correct techniques and build confidence.
• Flexible training options. Choose from in-person, blended, or remote learning formats to fit your schedule and learning style.
• Skill development. Learn to perform high-quality chest compressions, deliver rescue breaths, and operate an AED effectively.
• Empowerment to act. Gain the confidence to take decisive action during emergencies, whether at home, work, or in the community.

HSI offers comprehensive training programs that encompass all these elements, ensuring participants are well-prepared to act swiftly and effectively during life-threatening emergencies.

When SCA strikes, every second matters — So does your training

Sudden cardiac arrest can happen to anyone, any time, in any place. It strikes without warning and can be fatal within minutes. However, with rapid recognition and immediate treatment from bystanders, lives can be saved.

By knowing the signs of SCA — such as sudden collapse, seizure-like activity, abnormal gasping, and unresponsiveness — you’re better equipped to take action. Immediately starting CPR and using an AED while waiting for professional medical services to arrive can give someone the best possible chance of survival.

You don’t have to be a medical professional to save a life. You just need the knowledge, the will to act, and the confidence to take that first step.

Ready to be the difference-maker? Take a CPR, AED, and First Aid class near you with an authorized HSI Instructor!

Already passionate about helping others? Take it a step further by becoming an HSI Instructor. Whether you’re leading safety efforts at your organization or want to teach classes in your community, you can be the one who turns bystanders into lifesavers.