Heart Attack vs. Sudden Cardiac Arrest: Understanding the Difference

Awake or Not Awake. That is the Question.

October is National Sudden Cardiac Arrest Awareness Month. Understanding the difference between heart attack and sudden cardiac arrest could help save lives. One way to understand the difference between the two conditions is this distinction: The heart attack victim is awake and the heart is beating. In contrast, the sudden cardiac arrest victim is not awake and the heart is not beating. To survive sudden cardiac arrest, the victim needs immediate CPR and treatment with a defibrillator. [1]

Sudden unexpected cardiac arrest is the third leading cause of death in the U.S. [2], affecting 326,200 people each year, including 6,000 youth [3]. On average, about 10 percent of victims survive, though nearly 40 percent survive when bystanders call 911, start CPR, and use automated external defibrillators, or AEDs, before emergency medical services (EMS) arrives at the scene. [4] 

It's a common misconception that heart attack and sudden cardiac arrest are the same thing. In reality, the two conditions are quite different. 

Heart attack, or myocardial infarction, occurs when part of the heart's blood supply is reduced or blocked, causing the heart muscle to become injured or die. Victims may complain of various symptoms including:

• Mild intermittent chest discomfort that lasts a few minutes and comes and goes over a period of days
• Pain or discomfort in one or both arms that spreads to the shoulders, upper back, neck or jaw
• Shortness of breath
• Nausea, sweating, lightheadedness
• A general sense of anxiety
• A tendency to deny that anything serious is happening.

Women sometimes experience additional symptoms including:

• Stomach or abdominal pain
• Weakness and overwhelming fatigue
• Swelling of the ankles and lower legs.

When someone has a heart attack, he or she is awake and the heart is beating. It's important to act right away to maximize the odds of survival and minimize permanent damage to the heart. Bystanders should call 911 and have the person lie down and rest until EMS arrives. 

While heart attack is often described as a "plumbing problem," sudden cardiac arrest is more of an "electrical problem" that prevents the heart from functioning effectively. Heart attacks can lead to sudden cardiac arrest, but there are many other causes as well, including congenital and electrophysiological abnormalities, severe heart failure, electrocution, and drug overdose.

When sudden cardiac arrest occurs, the heart stops beating altogether. As a result, blood is no longer pumped throughout the body, including the brain. The person suddenly passes out, loses consciousness, and appears lifeless -- except for abnormal gasping, which may last several minutes. Sometimes victims experience seizure activity at the onset of the event.

The sudden cardiac arrest victim is not awake and the heart is not beating. If no one provides immediate help, the victim will die within minutes.

When sudden cardiac arrest occurs, it is critically important for bystanders to call 911, give CPR, and use the nearest AED.

This is lifesaving care that anyone can provide. While it is best to be trained in CPR and the use of AEDs, even without formal training, bystanders can call 911, follow dispatcher instructions, push hard and fast on the center of the victim's chest, and follow the directions on the AED while waiting for EMS to arrive.

Sometimes people hesitate to help because they are afraid they might do something wrong and hurt the victim. But since the cardiac arrest victim is clinically dead and cannot get any worse, bystander actions can only help. In addition, state and federal Good Samaritan laws provide protection to bystanders who render aid to sudden cardiac arrest victims in good faith.

Risk factors for sudden cardiac arrest include:

• A previous heart attack
• A previous episode of cardiac arrest
• A low (<35 percent) ejection fraction (the heart's ability to pump blood)
• Underlying heart conditions such as coronary artery disease, congenital heart disease (e.g., hypertrophic cardiomyopathy), electrophysiological abnormalities (e.g., long QT syndrome, Wolff-Parkinson-White disease, Brugada syndrome)
• Severe heart failure
• Marked changes in electrolytes in the blood
• A tendency to faint
• Hyperthyroidism
• Electrocution
• Drug abuse
• A family history of heart disease or stroke, especially having relatives who died suddenly before age 50.

If your loved ones have one or more of these risk factors, they may be at risk for sudden cardiac arrest. If this is the case, they should see a cardiologist or heart rhythm specialist (electrophysiolgist) for an evaluation. The physician may recommend implantable cardioverter defibrillator therapy, medications, or other measures to prevent sudden cardiac death.

In summary, heart attack victims are awake and typically experience discomfort or pain. While they do not need CPR or treatment with a defibrillator, it's essential to call 911 so they can be transported immediately to the hospital. In contrast, sudden cardiac arrest victims are not awake and need immediate CPR and treatment with a defibrillator. You can save a life by learning to recognize these conditions and being prepared to take appropriate action.

-By Mary M. Newman, MS

See Huffington Post blog here.

For more information, visit http://www.sca-aware.org.

REFERENCES: 

[1] Sudden Cardiac Arrest Foundation. Sudden cardiac arrest and heart attack: Understanding the difference. http://www.sca-aware.org/blog/scafoundation/sca-and-heart-attack-unders….

[2] IOM (Institute of Medicine). 2015. Strategies to improve cardiac arrest survival: A time to act. Washington, DC: The National Academies Press.

[3] Heart Disease and Stroke Statistics -- 2015 Update: A Report From the American Heart Association. Circulation. 2015; 131: e29-e322. Published online before print December 17, 2014, doi: 10.1161/CIR.0000000000000152.

[4] Weisfeldt ML, Sitlani CM, Ornato JP, et al. Survival after application of automated external defibrillators before arrival of the emergency medical system: Evaluation in the Resuscitation outcomes consortium population of 21 million. J Am Coll Cardiol. 2010;55(16): 1,713-1,720.