What Is Cardiac Arrest?

What Is Cardiac Arrest?

Cardiac arrest happens when your heart abruptly stops effectively pumping blood out to the rest of the body, resulting in loss of a pulse and oftentimes death. The American Heart Association estimates that in the U.S., cardiac arrest is responsible for over 430,000 deaths per year. Cardiac arrest is often caused by underlying health conditions, such as heart disease, electrolyte abnormalities, or pulmonary embolism. In some cases, you can have a cardiac arrest due to drowning, blunt force trauma, and drug overdose.

Types of Cardiac Arrest

There are different types of cardiac arrest, which include:

  • Cardiac arrest: The heart abruptly stops working, resulting in a loss of blood flow and circulation
  • Sudden cardiac arrest: A cardiac arrest that occurs unexpectedly
  • Sudden cardiac death: Occurs when a cardiac arrest results in death
  • Aborted sudden cardiac death: Happens when CPR and medical intervention effectively prevents death caused by a cardiac arrest

Signs and Symptoms

If you witness someone who suddenly collapses, is gasping, or is unable to breathe, err on the side of caution and suspect that they are undergoing a cardiac arrest. At this time, it’s paramount to begin CPR. This could be the difference between life and death. It is estimated that immediate CPR can double or triple the chances of survival.

Be on the lookout for the following signs of cardiac arrest:

  • Sudden collapse
  • Loss of consciousness
  • Inability to wake up even after shaking them or shouting
  • Gasping for air or lack of breathing
  • Not having a pulse


Cardiac arrest occurs when the heart is suddenly unable to deliver blood to the body. Your organs and tissues require a constant supply of oxygen from the blood to survive. The brain is especially vulnerable to periods of low oxygen—a complication known as ischemia. Lack of blood flow to the brain, called cerebral ischemia, leads to collapse and loss of consciousness within seconds during a cardiac arrest.

The underlying medical conditions that can lead to cardiac arrest include:

  • Heart conditions: Includes heart attack, cardiac tamponade, cardiomyopathy, congenital heart disease, and myocarditis
  • Pulmonary embolism: A blood clot in the lungs
  • Electrolyte abnormalities: Conditions such as hyperkalemia, hypokalemia, and hypomagnesemia

You can also experience cardiac arrest due to:

  • Trauma, including commotio cordis
  • Drug overdose
  • Drowning
  • Bleeding
  • Asphyxiation or obstruction of the airway


Determining the underlying cause of a cardiac arrest is important so that your healthcare provider can offer the appropriate treatment. During a cardiac arrest or shortly after resuscitation, the following labs, heart studies, and imaging tests can help diagnose or rule out conditions that caused the cardiac arrest to occur:

  • Electrocardiogram (ECG or EKG) to look for signs of irregular heart rhythms and heart attack
  • Lab studies including blood chemistry tests for electrolytes and blood gas studies for blood pH and oxygen levels
  • Chest imaging such as X-ray and computed tomography angiography (CTA) to identify lung problems like a pulmonary embolism or pneumothorax
  • Echocardiogram (a heart ultrasound) to look for cardiac tamponade (fluid around the heart that impairs cardiac output) and structural heart disease
  • Other heart tests such as cardiac catheterization to identify blockages in coronary arteries (your heart’s blood vessels) or an electrophysiology study to look for underlying heart rhythm problems


During a cardiac arrest, there is no heartbeat to provide blood flow to the brain and other major organs. Every second counts, so it’s essential to recognize cardiac arrest and start immediate cardiopulmonary resuscitation (CPR). CPR involves pressing on the chest to provide blood flow to give someone the best chance at surviving. Without CPR, cardiac arrest is fatal.

Here are brief steps to perform hands-only CPR:

  • Call for help: Call 9-1-1, and if in a public place, request an AED (automatic external defibrillator)
  • Get in position: Ensure the person is lying flat on the ground, kneel beside them, and lock your elbows and keep your arms straight before starting compressions
  • Press hard and fast on the center of the person’s chest continuously: The rate of compressions should be between 100 to 120 compressions per minute, with strength enough to depress the chest about 2 inches down
  • Continue CPR: Keep going until medical help arrives


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