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10 Things That Happen When Your Heart Stops

You've seen it on the big screen—the dramatic moment when the "doctor" announces that the heart stopped. What does it mean in real life? Cardiologists tell what actually happens in your body.

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You’ve had an SCA

Sudden cardiac arrest (SCA) is “medicalese” for “your heart stopped.” As the name implies, it can occur suddenly without warning. There are many causes of SCA, including irregular heart rhythms and/or genetic abnormalities; the condition can result in sudden death but doesn’t always. Make sure you remember these 7 easy CPR steps.

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You are not having a heart attack

Check out the difference between a heart attack and cardiac arrest: A heart attack may precede or follow SCA, but they are not the same. According to the American Heart Association, a heart attack is a circulation problem—a blockage in the blood flow to the heart—but the heart can continue to pump. With SCA, the problem is an electrical disturbance that disrupts your heart beat.

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Your pacemaker is malfunctioning

The sinus node, located in your heart’s upper right chamber, is a specialized group of cells that generate electrical impulses through the heart, explains Iosif Gulkarov, MD, a cardiothoracic surgeon at the Heart Institute, Staten Island University Hospital in Staten Island, New York. This cluster of cells functions as your heart’s natural pacemaker; when the cells misfire, you get an arrhythmia. There is an impairment in your heart’s rhythm that interferes with the job of pumping blood and maintaining circulation. Make sure you know these things that can mess up your heart’s rhythm.

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Your heart may be quivering

The most common, and potentially lethal, arrhythmia is ventricular fibrillation, a quick and chaotic rhythm during which the heart’s lower chambers begin quivering, bringing your circulation to a halt.

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Your heart may be racing or slowing

Aside from ventricular fibrillation, other abnormal rhythms that can cause the heart to stop pumping blood include ventricular tachycardia, which is marked by a quickened heartbeat (above 100 beats per minute) that is out of sync with the heart’s upper chambers. Brachycardia is a heart rate that has slowed below 60 beats per minute.

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You may feel and remember nothing

Sometimes the heart stops pumping blood and there are no symptoms. “Other people may report that they felt dizzy, tired, cold, or weak right before they passed out,” says Dr. Gulkarov. An onlooker may notice the person’s eyes rolling back and/or witness a seizure. “The heart is tasked with pumping blood to all parts of the body including the brain, and when the brain doesn’t get blood, a person can seize or pass out,” he says. “The first cells to die during cardiac arrest are brain cells.”

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SCA is not a death sentence

At least not if someone acts quickly: If you witness someone pass out, try to rouse them, and if you can’t, check their pulse. “If there is no pulse, start cardiopulmonary resuscitation (CPR or chest compressions) immediately and call 911,” says Konstantinos Dean Boudoulas, MD, an interventional cardiologist at The Ohio State University Wexner Medical Center in Columbus. CPR manually gets the blood moving through the body and is a person’s best shot at survival. Familiarize yourself with this CPR guide so you know what to do if someone experiences a life-threatening emergency. Ninety percent of people who suffer out-of-hospital cardiac arrests die, but CPR, if performed in the first few minutes, can triple a person’s odds of survival, according to the American Heart Association. Cardiac arrest can also occur in the hospital. Survival rates are rising for people who have a cardiac arrest while in the hospital, but if it happens at night or on a weekend, you’re more likely to die, according to a study the Journal of the American College of Cardiology.

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You need a restart STAT

Defibrillators are everywhere today (schools, airports, hotels, restaurants, gyms—you name it), and they save lives. Defibrillators can instantly analyze heart rhythms to determine if they are “shockable,” which means reversible. Defibrillation should be started as soon after CPR as possible. Further treatment may be needed after an abnormal rhythm is reversed to keep it from coming back. If this doesn’t work, the individual is placed on an automated CPR machine and transferred to their hospital where they are immediately placed on a heart-lung bypass machine for support. This is known as extracorporeal cardiopulmonary resuscitation (ECPR), and it allows interventional cardiologists to look for reversible causes of the arrest. “It’s a game changer,” explains Dr. Boudoulas.

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You need a diagnosis

Asystole is a cardiac arrest-causing rhythm where there is no electrical activity visible on the electrocardiogram (ECG) monitor, explains Dr. Boudoulas. Pulseless electrical activity (PEA) occurs when the ECG shows a heart rhythm that should produce a pulse but does not. “Essentially, sudden cardiac death results from arrhythmia indirectly or directly,” he says. “Heart disease can cause a heart attack, which can lead to arrhythmia.” Take necessary precaution with these 30 ways to prevent heart disease.

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The bottom line

Survival depends on the cause of the arrest as well as the timeliness of treatment. Each year, 325,000 adults die from SCA in the United States, according to Cleveland Clinic. Knowing CPR and acting quickly provides the best chance of survival in the face of cardiac arrest. However, you may not even know you’re at risk. Look out for these silent signs of heart trouble you shouldn’t ignore.