Signs and Symptoms of Sudden Cardiac Arrest

How to Tell if Someone Needs CPR

Midsection Of Man Resuscitating Friend Lying On Road

Jaromir Chalabala / EyeEm / Getty Images

udden cardiac arrest is a serious and life-threatening medical emergency characterized by a sudden loss of consciousness, breathing, and pulse. This may be preceded by dizziness, shortness of breath, and a racing heartbeat, though some experience no warnings at all. The symptoms of cardiac arrest come on suddenly and must be treated immediately.

Cardiac arrest is usually caused by an electrical disturbance that disrupts the pumping action of the heart, stopping blood flow to the rest of the body. Prompt performance of cardiopulmonary resuscitation (CPR) and use of a defibrillator, which delivers an electrical pulse to the chest to restart the heart, are essential. Any delay in care can increase one's risk of death.

According to a report from the American Heart Association, more than 356,000 out-of-hospital cardiac arrests occur in the United States each year. Nearly 90% of them are fatal.

Despite this, early recognition of cardiac arrest symptoms, along with a fast, appropriate response, can significantly increase one's chances of survival.

Preceding Symptoms

Some people who experience cardiac arrest have some sense that something is wrong ahead of time. In some cases, cardiac arrest will be preceded by warning symptoms which may include

  • Difficulty breathing or shortness of breath
  • Chest pain
  • Nausea and/or vomiting
  • Irregular or racing heartbeat (arrhythmia)
  • Lightheadedness and dizziness
  • Passing out, fainting, or losing consciousness

These symptoms, of course, can be confused with those of several other conditions.

Often, however, people do not realize that there is a problem until the actual cardiac arrest event itself is occurring.

Classic Symptoms

Depending on the cause, cardiac arrest can mimic other conditions. For example, someone may have convulsions that look like a seizure, or you may presume that someone is choking if they start gasping and collapse. Regardless, symptoms of in-progress cardiac arrest occur quickly and are dramatic.

There are three signs that, when present together, can help you distinguish a cardiac arrest from another emergency. Even if you're in doubt about what you're witnessing someone experience, seek emergency medical attention.

Sudden Loss of Consciousness

The stoppage of blood flow to the brain deprives the brain of the oxygen and sugars it needs to function, resulting in the loss of consciousness (syncope). This will occur within seconds of the heart stopping.

Unlike other forms of syncope, in which a person may be suddenly or intermittently aroused, loss of consciousness with cardiac arrest will persist until heart function and circulation are restored.

Stoppage of Breathing

With cardiac arrest, the loss of consciousness will be accompanied by the complete stoppage of breathing. This happens because the brain effectively shuts down involuntary bodily functions needed to survive, including breathing, when it is abruptly deprived of oxygen.

At the onset of cardiac arrest, there will often be agonizing gasping motions, called agonal respiration, in which the person seems suddenly deprived of air before suddenly collapsing. Agonal respiration is not actually breathing, per se, but rather a reflex of the brainstem as it is confronted with a cataclysmic breakdown of heart function.

Unless heart function and respiration are restored within minutes, permanent brain damage can occur.

Absence of a Pulse

The absence of a pulse is the central sign of cardiac arrest. Unfortunately, this is the symptom often missed by lay rescuers who don't know how to find a pulse. Don't waste time looking for a pulse if the person has already collapsed and stopped breathing.

Even professional rescuers are being asked to spend fewer than 10 seconds checking for pulse and initiate CPR and defibrillation immediately if the person has stopped breathing.

If a person has stopped breathing, call 911 and start CPR chest compressions at a rate of 80 to 100 beats per minute. Even if it turns out not to be cardiac arrest, CPR will not harm the individual.

Outcomes After Cardiac Arrest

Early CPR with defibrillation is the only way to reverse cardiac arrest. Speed is of the essence if a person is to survive. For every minute that passes without defibrillation, the chances of survival decrease by anywhere from 7% to 10%. If emergency services arrive and administer defibrillation, survival rates are as high as 49%.

Unfortunately, the more time that passes between the onset of cardiac arrest and treatment, the more likely it is for the cardiac arrest to lead to permanent death.

A Word From Verywell

If you encounter a person who has collapsed and is no longer breathing, don't waste your time trying to figure out whether it is cardiac arrest or not. Simply act and recruit others around you to help. Cardiac arrest won't suddenly reverse itself and requires immediate hands-on intervention. Call 911 right away and, if you're able, perform CPR until help arrives.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: Adult basic and advanced life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020;142(16_suppl_2). doi: 10.1161/CIR.0000000000000916

  2. National Heart, Lung, and Blood Institute; National Institutes of Health. Sudden Cardiac Arrest.

  3. Benjamin EJ, Virani SS, Callaway CW, et al. Heart disease and stroke statistics—2018 update: a report from the American Heart Association. Circulation. 2018;137(12). doi: 10.1161/CIR.0000000000000558

  4. Chan J, Rea T, Gollakota S, Sunshine JE. Contactless cardiac arrest detection using smart devices. npj Digital Medicine. 2019;2(1):1-8.

  5. Welbourn C, Efstathiou N. How does the length of cardiopulmonary resuscitation affect brain damage in patients surviving cardiac arrest? A systematic review. Scand J Trauma Resusc Emerg Med. 2018;26(1):77.

Additional Reading