What is the difference between a heart attack and a cardiac arrest? One is about the plumbing, the other is about the wiring

In July 2023, rising US basketball star Bronny James collapsed on the court during training and was hospitalized. The 18-year-old athlete, son of famous LA Lakers veteran LeBron James, had suffered a cardiac arrest.

Many media outlets incorrectly referred to the event as a “heart attack” or used the terms synonymously.

Cardiac arrest and heart attack are different but overlapping concepts related to the heart.

With some background knowledge about how the heart works, we can see the differences and connections.

Understanding the heart

The heart is a muscle that contracts to work as a pump. When it contracts, it pumps blood – which contains oxygen and nutrients – to all the tissues in our body.

In order for the heart muscle to work effectively as a pump, it must be supplied with blood via the coronary arteries. If these arteries are blocked, the heart muscle does not receive the blood it needs.

This can cause damage or death to the heart muscle and the heart to no longer pump properly.

Heart attack or cardiac arrest?

Simply put, a heart attack, technically known as a myocardial infarction, describes injury or death of the heart muscle.

Cardiac arrest, sometimes called sudden cardiac arrest, occurs when the heart stops beating or, in other words, no longer performs its pumping function effectively.

In other words, both are related to the heart not working as it should, but for different reasons. As we will see later, one can lead to the other.

Why do they happen? Who is at risk?

Heart attacks are usually the result of blockages in the coronary arteries. This is sometimes called coronary artery disease, but in Australia it is more commonly referred to as ischemic heart disease.

The underlying cause, in about 75% of people, is a process called atherosclerosis. This is where fatty and connective tissue build up in the walls of the coronary arteries, forming plaque. The plaque can block the blood vessel or, in some cases, lead to the formation of a blood clot.

Atherosclerosis is a long-term, insidious process with a number of risk factors that can affect anyone. High blood pressure, high cholesterol, diet, diabetes, stress and your genes are all involved in this process of plaque formation.

Other causes of a heart attack include coronary artery spasms (which cause the arteries to narrow), chest trauma, or anything else that reduces blood flow to the heart muscle.

Regardless of the cause, a blockage or reduction in blood flow through these tubes can result in the heart muscle not receiving enough oxygen and nutrients, which can cause heart muscle cells to become injured or die.

However, cardiac arrest is the result of abnormal heart rhythms that make it difficult for the heart to pump blood effectively throughout the body. These abnormal heart rhythms are generally due to electrical malfunctions in the heart. There are four different types:

• ventricular tachycardia: a fast and abnormal heart rhythm in which the heart beats more than 100 beats per minute (the normal heart rate in adults is generally 60-90 beats per minute at rest). This fast heart rate prevents the heart from filling with blood and thus pumping adequately

• Ventricular fibrillation: Instead of regular beats, the heart trembles or “fibrillates” and resembles a sack of worms, resulting in an irregular heartbeat of more than 300 beats per minute

• pulseless electrical activity: occurs when the heart muscle does not produce enough pumping power after electrical stimulation, which leads to no pulse

• Asystole: the classic flat heart rhythm that you see in movies and which indicates no electrical activity in the heart.

Cardiac arrest can be caused by numerous underlying conditions, both cardiac and non-cardiac, such as drowning, trauma, asphyxia, electrocution, and drug overdose. James' cardiac arrest was attributed to congenital heart defect, a heart condition he was born with.

However, among the many causes of cardiac arrest, ischemic heart disease, such as a heart attack, is the most common cause, accounting for 70% of all cases.

So how can a heart attack cause cardiac arrest? You'll recall that a heart attack can cause damage to the heart muscle or parts of it to die. This damaged or dead tissue can affect the heart's ability to conduct electrical signals, increasing the risk of abnormal heart rhythms and potentially causing cardiac arrest.

Although a heart attack is a common cause of cardiac arrest, cardiac arrest does not generally result in a heart attack.

What do they look like?

Because cardiac arrest occurs when the heart suddenly stops pumping blood, the most common signs and symptoms include sudden loss of consciousness, absence of pulse or heartbeat, cessation of breathing, and pale or bluish skin.

However, common signs and symptoms of a heart attack include chest pain or discomfort, which may also spread to other parts of the body such as the arms, back, neck, jaw, or abdomen. Also common are shortness of breath, nausea, dizziness, paleness, and sweating.

What is the take-home message?

Although both heart attack and cardiac arrest are heart diseases, they differ in their mechanisms and consequences.

A heart attack is like a blockage in a house's water pipe. A cardiac arrest, on the other hand, is like an electrical malfunction in the house's wiring.

Despite their different nature, both conditions can have serious consequences and require immediate medical attention.

This article is republished from The Conversation under a Creative Commons license. Read the original article.