What Is Ischemia? - Definition, Causes & Symptoms

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson defines the concept of ischemia. Then you'll learn the major reasons for why it might occur and the signs and symptoms of various different forms of ischemia.

What is Ischemia?

It can affect your heart. It can affect your intestines. It can affect any part of your body. And if it does, and it's prolonged and severe enough, it can end up triggering a sequence that leads to your death. It's called ischemia, an inadequate supply of oxygenated blood to all or part of a tissue or organ as a result of an obstructed or constricted blood vessel. Ischemia itself comes from the Greek 'ischein', which means to hold back and '-emia', which refers to blood or a condition of the blood.

Let's learn about its causes, signs and symptoms.


It's important to note right from the start that ischemia is a general term. It doesn't refer to any particular organ or tissue. It can be qualified; however, to refer to a particular structure. For instance, myocardial ischemia refers to ischemia of the heart muscle. More on that later.

Regardless though, the causes of any specific form of ischemia fall into two major categories given away by the definition itself:

1. Obstructed blood vessels

2. Constricted/narrowed blood vessels

What can obstruct a blood vessel? A blood clot (thrombus), a gas bubble (air embolism), and a piece of fat (fat embolism) to name a few. What can constrict a blood vessel? Blood vessel disorders, like atherosclerosis or a blood vessel spasm (vasospasm). In atherosclerosis, fatty plaques narrow the blood vessel. In a blood vessel spasm, the blood vessel suddenly constricts all by itself, sometimes for no known reason.

And here's another important note. Our definition used the term 'oxygenated blood'. Oxygenated blood is carried to a tissue via arteries. Deoxygenated blood is carried away from the tissues via veins. So you'd logically think that an obstructed artery would be a cause of ischemia, and you'd be right. But suddenly obstructed or constricted veins can cause ischemia as well even though they don't deliver oxygenated blood to the tissue.

Why? If the outflow of blood is obstructed, congestion sets in. This means oxygenated (arterial) blood has a tougher time getting through all that congestion and into the tissue. This means ischemia sets in anyways.

Signs & Symptoms

The signs and symptoms of ischemia will vary depending on what part of the body is affected and the severity and duration of the ischemia. Let's take a few examples:

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