Signs and Symptoms of Sudden Cardiac Arrest

How to Tell if Someone Needs CPR

Midsection Of Man Resuscitating Friend Lying On Road

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Sudden 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.


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 a condition known as severe autonomic hyperreflexia, in which the involuntary nervous system overreacts, causing:

  • Sudden anxiety and apprehension (a "feeling of doom")
  • Irregular heartbeat (arrhythmia)
  • A pounding headache
  • Flushing and profuse sweating
  • Sudden nasal congestion
  • Lightheadedness and dizziness
  • Pupil dilation
  • Confusion


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 20 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 the heart function.

Unless heart function and respiration are restored within five 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.

In some parts of the country, even professional rescuers are being asked to ignore the pulse and initiate CPR and defibrillation 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, it is rare for resuscitation to be successful if more than 10 minutes have passed without treatment following the onset of cardiac arrest.

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.

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