What Causes Sudden Cardiac Arrest?

What Causes Sudden Cardiac Arrest?

chest pain graphic

Sudden Cardiac Arrest (SCA) is the leading cause of death in the U.S. And 350,200 people in the U.S. experience SCA, and nine out of 10 victims die. What actually causes Sudden Cardiac Arrest that so many people can suffer from? We get the question quite frequently and we have compiled a list of known causes to SCA for your convenience. Take a look, and schedule a talk with your doctor to see if you need to be cautious of the following risk factors.

1) Physical Stress

Certain types of physical stress can cause your heart’s electrical system to fail. During intense physical activity, the hormone adrenaline is released and can trigger SCA in those who have heart problems. Very low blood levels of potassium or magnesium can also play an important role in the heart’s electrical signaling.

2) Structural Changes in the Heart

Changes in the heart’s normal size or structure may affect its electrical system. Examples of such changes include an enlarged heart due to high blood pressure or advanced heart disease. Heart infections also may cause structural changes in the heart.

3) Heart Attack

If a heart attack occurs, often as a result of severe coronary artery disease, it can trigger ventricular fibrillation (VF) and sudden cardiac arrest. In addition, a heart attack can leave behind areas of scar tissue. Electrical short circuits around the scar tissue can lead to abnormalities in your heart rhythm.

4) Hyperkalemia (High Potassium)

Hyperkalemia is the medical term that describes a potassium level in your blood that’s higher than normal. Potassium is a chemical that is critical to the function of nerve and muscle cells, including those in your heart.

5) Arrhythmias

The four main types of arrhythmia are: 1) Premature (extra) Beats, 2) Supraventricular Arrhythmias, 3) Ventricular Arrhythmias, and 4) Bradyarrhythmias.

  • Premature (Extra) Beats – Premature beats are the most common type of arrhythmia. They’re harmless most of the time and often don’t cause any symptoms.
  • Supraventricular Arrhythmias – Supraventricular Arrhythmias are tachycardias (fast heart rates) that start in the atria or atrioventricular (AV) node. The AV node is a group of cells located between the atria and the ventricles. Types of Supraventricular Arrhythmias include:
    • AF – Atrial Fibrillation is the most common type of arrhythmia. AF occurs if rapid, disorganized electrical signals cause the heart’s two upper chambers, called the atria, to fibrillate.
    • AFL – Atrial flutter is the most common abnormal heart rhythm. AFL occurs if the upper chambers of the heart beat too fast, which results in atrial muscle contractions that are faster than and out of sync with the lower chambers.
    • PSVT – Paroxysmal supraventricular tachycardia is a regular, fast (160 to 220 beats per minute) heart rate that begins and ends suddenly and originates in heart tissue other than that in the ventricles.
    • WPW – Wolff-Parkinson-White syndrome is where an extra electrical pathway between your heart’s upper and lower chambers causes a rapid heartbeat. The extra pathway is present at birth and fairly rare. This syndrome is often harmless, however, doctors might recommend further evaluation before children participate in high-intensity sports.
  • Ventricular Arrhythmias
    • Brugada Syndrome – a condition that can lead to irregular heartbeats in the heart’s lower chambers. If untreated, the irregular heartbeats can cause fainting, seizures, difficulty breathing, or sudden death.
    • Catecholaminergic polymorphic ventricular tachycardia – a disorder of the calcium channels in the heart muscle, resulting in problems with electrical signalling and irregular heartbeats. As the heart rate increases in response to physical activity or emotional stress, it can trigger an abnormally fast and irregular heartbeat called ventricular tachycardia.
    • Ventricular Fibrillation (VF) – the electrical signals that control the lower chambers of the heart (ventricles) become chaotic. This sends the ventricles into fibrillation, an extremely rapid and irregular quivering that cannot effectively pump blood to the body.
  • Bradyarrhythmias – Bradyarrhythmias occur if the heart rate is slower than normal. If the heart rate is too slow, not enough blood reaches the brain.

6) Inherited Disorders

A tendency to have arrhythmias runs in some families. This tendency is inherited, which means it’s passed from parents to children through the genes. Members of these families may be at higher risk for SCA. Examples of inherited disorders that makes you more likely to have arrhythmias are:

  • Long QT syndrome (LQTS) –  LQTS is a disorder of the heart’s electrical activity. Problems with tiny pores on the surface of heart muscle cells cause the disorder. LQTS can cause sudden, uncontrollable, dangerous heart rhythms.
  • Cardiomyopathy (enlarged heart) – Cardiomyopathy is a condition which affects the ability of the heart muscle to pump effectively. There are different types of cardiomyopathies:
    • Dilated Cardiomyopathy – This is the most common type of cardiomyopathy. One or more chambers of the heart become enlarged, and the muscles that make up the walls of the heart become stretched and thinner than normal. This stretching further weakens the muscles, and the heart is not able to pump blood as strongly.
    • Hypertrophic Cardiomyopathy – Muscles in the heart become abnormally thickened, and the heart has to work harder to push the same amount of blood through the body. In obstructive hypertrophic cardiomyopathy, the thickened muscles push into a chamber of the heart, blocking blood flow and sometimes causing the mitral valve of the heart to leak.
    • Restrictive Cardiomyopathy – In this rare type, the heart muscles become stiff, and the ventricles of the heart are not able to relax and completely fill with blood between heartbeats.
    • Arrhythmogenic Right Ventricular Cardiomyopathy – Heart muscle cells are replaced by scar tissue or fat, leading to disturbances in the electrical signalling of the heart. These disturbances can cause sudden cardiac death.
  • Coronary Heart Disease (CHD) – CHD is a disease in which a waxy substance called plaque builds up in the coronary arteries. These arteries supply oxygen-rich blood to your heart muscle. When plaque builds up in the arteries, the condition is called atherosclerosis. Arteries are blood vessels that carry oxygen-rich blood to your heart and other parts of your body. Eventually, an area of plaque can rupture and may cause a blood clot to form on the plaque’s surface. A blood clot can partly or fully block the flow of oxygen-rich blood to the portion of heart muscle fed by the artery. This causes a heart attack, during which some heart muscle cells die and are replaced with scar tissue. The scar tissue damages the heart’s electrical system. As a result, electrical signals may spread abnormally throughout the heart. These changes to the heart increase the risk of dangerous arrhythmias and SCA.

7) Scarring

Rhythm problems can often be traced to scarred heart muscle. “Scarring causes the heart’s electrical signals to become confused and fragmented,” explains Dr. Wilkoff. The most common causes are coronary artery disease and cardiomyopathy. Heart attacks starve the heart muscle, causing tissue death and scarring. Viral infections, hereditary or autoimmune conditions and chemical toxicity can also damage and scar the heart muscle.

8) Mitral Valve Prolapse  

Mitral Valve Prolapse (MVP) occurs when the leaflets of the mitral valve bulge (prolapse) into the heart’s left upper chamber (left atrium) like a parachute during the heart’s contraction.

9) Drug Abuse

Most illegal drugs can have adverse cardiovascular effects, ranging from abnormal heart rate to heart attacks. Injecting illegal drugs also can lead to cardiovascular problems, such as collapsed veins and bacterial infections of the blood vessels and heart valves.

10) Electrocution  

Electrical shock is a leading cause to CA, it is the injury caused by contact with electric current passing through the human body causing undesirable effects ranging from simple burns to death.

11) Commotio Cordis

A disruption in the heart rhythm that occurs from a blunt blow to the chest. It must be directly over the heart at a critical time in the heart beat (10-30ms)

12) A low ejection fraction

Every contraction pushes blood out of the two pumping chambers (ventricles). When the heart relaxes, the ventricles refill with blood. The ejection fraction (EF) refers to the amount, or percentage, of blood that is pumped (or ejected) out of the ventricles with each contraction. If you have heart failure with an ejection fraction of 35 percent or less, your heart can’t pump out enough blood with each beat. This disrupts your heart rhythm and increases the risk of sudden cardiac death.

13) Poorly managed heart failure symptoms

“If you have heart failure symptoms (shortness of breath and exercise intolerance) with or without a low ejection fraction, you need medicine,” he says. Drugs such as ACE inhibitors and beta blockers will keep your heart from working too hard, improve its function and lower your risk of SCA.


If you can think of any other causes, leave us a comment! If you are convinced that you are in need of an AED, give us a call at 800-580-1375. If you still have questions, you can always leave us a comment or email us at customerservice@aedbrands.com


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