Low Potassium & Heart Attacks

Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

We are going to learn about one of the most important electrolytes in our body, potassium. Normal potassium levels, what potassium does, and the effects that may be seen with low potassium will be described.


What advice are you given any time you sweat a lot from playing sports or experience vomiting and/or diarrhea for any period of time? The advice is something along the lines of drink a sports drink to replace lost water and electrolytes. Electrolytes are the chemical ions in your body that help the nerves and muscles function.

Tomatoes contain potassium
picture of tomatoes

Sodium and potassium are two of the main electrolytes that are crucial to nerve and muscle function. You are probably aware that sodium is one of the components of regular table salt. Potassium is a chemical that is found regularly in a lot of the foods we eat, such as bananas, avocados, and tomatoes. We usually get potassium and other electrolytes that we need in our bodies from consuming foods and drinks that contain them.

Our bodies function best when our blood potassium level is 3.5 - 5.0 mEq/L of blood. When the levels get too high, problems can arise, and the same is true when levels get too low.

The Heart

Many muscles exist in the body, but none are arguably more important than the heart. It has the vital function of pumping oxygenated blood throughout the body in order to supply the organs with oxygen and nutrients they need to function. The heart muscle itself also receives oxygenated blood from this action.

The heart muscle requires potassium to function
Diagram of the heart

The heart is one of the muscles in the body that requires both potassium and sodium in order to contract. The cells of the heart contract in response to the movement of potassium and sodium across their membranes. This only occurs the way it is supposed to when these electrolytes are in the right amounts. Things can go wrong if the amounts are too high or too low. Let's go over what happens when the potassium levels are too low.

Low Potassium and Heart Attack

Several heart problems may come to mind when you think about something not going right with the heart like cardiac arrest, heart failure, cardiac arrhythmia, and heart attack. Low potassium, called hypokalemia, could directly or indirectly cause each of these to happen. You can remember the term hypokalemia by remembering its word parts. The prefix hypo- means low, the word root kal- means potassium, and the suffix -emia means blood or blood condition.

Since the heart muscle needs potassium in order to contract, not having enough potassium may cause the heart to stop contracting, which is cardiac arrest. Once the heart is not pumping, then none of the body's organs, including the heart itself, are getting the blood supply that they need. Remember that the loss of blood supply to the heart muscle causes the death of heart tissue, which is a myocardial infarction, or what most refer to as a heart attack. This usually only happens when potassium levels are very low.

A heart attack can occur indirectly due to hypokalemia
Diagram of a heart attack

Potassium levels can be low without being so low that the heart stops contracting. Sometimes the low levels cause the heart to pump blood ineffectively in a condition known as heart failure. Heart failure could lead to a heart attack since blood is not moving as it should and could begin to clot. Blood clots that form or flow and get stuck in the coronary arteries could block the blood supply and cause a heart attack.

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