Hyperkalemia ECG Changes: Findings and Progressions
Hyperkalemia ECG changes made easy! Use this simple arrow trick to remember the progression of EKG findings seen with hyperkalemia, along with the effects on the heart. Great for students, nursing, USMLE, NCLEX, and more!
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Hyperkalemia: Definition & Levels
Potassium plays an important role in the human body and is required for many cells to function properly.
The heart is one organ in particular that relies on potassium to perform.
Potassium is involved in cardiac conduction, which allows our heart to contract and pump blood forward.
Changes to normal potassium levels in the blood can affect cardiac function.
For example, elevated potassium levels in the blood (hyperkalemia) can impact the cardiac conduction system, which can lead to changes seen on EKG.
In this lecture, we will review the main EKG changes that occur in hyperkalemia along with the mechanism behind those findings.
You will also learn a simple trick to remember these changes!
There is a table at the bottom of this post summarizing everything, so make sure to read until the end to not miss out!
Leave a comment down below if you find this trick useful!
Hyperkalemia Definition
Hyperkalemia is the medical term used to describe higher than normal potassium levels in the blood.
The definition makes sense if we break down the word.
We know from our medical terminology lecture that the prefix “hyper” means above normal, excess, high, or elevated.
The term “kalemia” refers to the presence of potassium in the blood.
Therefore, hyperkalemia is defined as elevated levels of potassium in the blood.
Hyperkalemia Definition: Elevated potassium levels in the blood. Prefix “Hyper” = Above normal; “Kalemia” = Presence of potassium in the blood
Normal Potassium Level
We know from our lecture on normal lab values that the normal range for potassium is about 3.5-5.0 mEq/L.
As a result, a value greater than 5.0 mEq/L will be considered high for most labs.
**Normal ranges can vary from lab to lab.
Hyperkalemia Effects on the Heart
Hyperkalemia can have many effects on the body, some of which are life-threatening.
As previously mentioned, potassium plays an important role in cardiac function.
In severe cases, hyperkalemia can lead to cardiac conduction abnormalities and arrhythmias (abnormal heart rates or rhythms).
Some arrhythmias can be life-threatening.
Therefore, it is important to be able to recognize hyperkalemia EKG changes, especially the early findings which will allow the condition to be treated promptly.
Let’s now review the EKG changes along with a simple trick to remember them!
Potassium Levels: The normal range for potassium is 3.5-5.0 mEq/L. Hyperkalemia (values > 5.0 mEq/L) can affect the heart.
*Normal lab values can vary
Hyperkalemia ECG Changes
The progression of EKG changes seen with hyperkalemia usually correlates with the severity of the potassium level.
Generally speaking, the first EKG changes start to occur when potassium levels are greater than 6.0 mEq/L.
However, this is not a hard-and-fast rule and EKG changes can happen sooner.
It is important to remember the EKG changes seen with hyperkalemia can vary from patient to patient.
Two patients could have identical high potassium levels, and one may have minimal EKG changes while the other has significant changes.
Having said that, there is a general progression of EKG changes seen with hyperkalemia.
The trick to remember these EKG changes is to draw a counterclockwise box of arrows like the one shown below.
Let’s walk through how the trick works!
Hyperkalemia ECG Changes: Use the arrow trick above to remember the progression of EKG changes in hyperkalemia.
1. Peaked T Waves
The arrow trick begins with the up arrow.
How can you remember to start with the up arrow?
Simply think of hyperkalemia, which is elevated levels of potassium in the blood.
Since we are dealing with increased levels of potassium, this will help you remember to start with the arrow pointing up.
One of the first EKG changes to occur in hyperkalemia is peaked T waves.
A peaked T wave refers to a T wave with a higher than normal amplitude that gives a tall, peaked or tented appearance.
The up arrow will help you remember peaked T waves.
Peaked T waves generally occur when potassium levels are about 5.5-6.5 mEq/L.
Again, this is not a hard-and-fast rule and there may be peaked T waves outside that range.
At potassium levels of 5.5-6.5 mEq/L, repolarization abnormalities can occur.
Remember from our EKG lecture that the T wave represents ventricular repolarization.
If you need a quick refresher on the different components of an EKG, then make sure to check out the lecture on EKGs Made Easy.
Since repolarization abnormalities occur at potassium levels of 5.5-6.5 mEq/L and the T waves represent ventricular repolarization, we see changes to the T wave morphology as a result.
To learn more about depolarization and repolarization, check out the lecture on Cardiac Action Potentials Made Easy.
Hyperkalemia ECG Changes: One of the first EKG findings in hyperkalemia is peaked T waves, due to repolarization abnormalities (Potassium 5.5-6.5 mEq/L)
2. Prolonged PR Interval
The arrow trick moves in a counterclockwise direction and illustrates the progression of EKG changes in hyperkalemia.
After the up arrow, we move to the arrow pointing left.
The next EKG changes to develop are PR interval prolongation and P wave widening.
PR interval prolongation refers to a longer than normal duration between the start of the P wave and the start of the QRS complex.
P wave widening refers to P waves that have a longer duration than normal.
The left arrow will help you remember the prolonged durations associated with the PR interval and P wave.
PR interval prolongation and P wave widening typically occur at potassium levels of 6.5-7.0 mEq/L.
Again, this is not a hard-and-fast rule but just an average.
At potassium levels of 6.5-7.0 mEq/L, progressive atrial paralysis can occur.
Remember from our EKG lecture the P wave represents atrial depolarization, and the PR interval represents the time from the start of the P wave (atrial depolarization) to the start of the QRS complex (ventricular depolarization).
In other words, the PR interval is the time it takes for an electrical impulse to depolarize the atria and travel through the atria and AV node to the ventricles.
Since progressive atrial paralysis occurs at potassium levels of 6.5-7.0 mEq/L and the PR interval and P wave both involve the atria, we see changes to the PR interval and P wave morphology as a result.
Hyperkalemia ECG Changes: The next EKG findings are PR interval prolongation and P wave widening, due to progressive atrial paralysis (Potassium 6.5-7.0 mEq/L)
3. Dropped P Waves
After the left arrow, we will move counterclockwise to the down arrow.
As the atrial paralysis progresses, eventually the P waves may disappear on EKG.
The phenomenon of disappearing P waves on EKG is often referred to as dropped P waves.
The down arrow will help you remember dropped P waves.
P waves may no longer be visible on EKG when potassium levels reach 7.0 mEq/L.
As previously mentioned, progressive atrial paralysis occurs at potassium levels of 6.5-7.0 mEq/L which is why we already saw PR interval prolongation and P wave widening.
Remember the P wave represents atrial depolarization, which is impacted by the atrial paralysis.
As potassium levels approach 7.0 mEq/L and the atrial paralysis worsens, we can start to see dropped P waves on EKG.
Hyperkalemia ECG Changes: As atrial paralysis progresses, the next EKG finding to occur is dropped P waves (Potassium 7.0 mEq/L)
4. Widened QRS Complex
Lastly, we will move counterclockwise to the arrow pointing right.
As potassium levels continue to rise, the next EKG change to develop is QRS widening.
A widened QRS refers to QRS complexes that have a longer duration than normal.
Think of severe hyperkalemia as grabbing on to each end of the EKG tracing and pulling outward to stretch it out.
The QRS complexes would widen, and eventually a sine wave pattern may form.
The right arrow will help you remember the widened QRS complexes.
At potassium levels of 7.0-9.0 mEq/L, conduction abnormalities can occur.
Conduction abnormalities may present as widened QRS complexes, sinus bradycardia, AV heart blocks, slow atrial fibrillation, bundle branch blocks, fascicular blocks, etc.
Remember from the EKG lecture the QRS complex represents ventricular depolarization.
Conduction abnormalities often affect ventricular depolarization, which is why we can see changes to the QRS morphology.
It is important to note the only sign of hyperkalemia may simply be sinus bradycardia (slow heart rate), so it is always good to keep hyperkalemia in the differential.
As potassium levels exceed 9.0 mEq/L, life threatening arrhythmias can develop.
This may include sine wave patterns, asystole, ventricular fibrillation (VF), or pulseless electrical activity (PEA).
Hyperkalemia ECG changes: The next EKG findings to progress are widened QRS complexes, arrhythmias, and heart blocks due to conduction abnormalities (Potassium 7.0-9.0 mEq/L). Sine wave pattern and life-threatening rhythms can also develop (Potassium > 9.0 mEq/L)
Hyperkalemia ECG Changes: Table
Below is a table summarizing the EKG changes that can occur in hyperkalemia along with the arrow trick, potassium levels, and mechanism behind those changes.
Hopefully this helps to bring it all together!
Hyperkalemia ECG Changes: Table summarizing EKG changes in hyperkalemia, along with the arrow trick, potassium levels, and mechanism for those changes.
Summary
Let’s briefly recap the table.
Up Arrow = Peaked T Waves
At potassium levels of about 5.5-6.5 mEq/L, peaked T waves may be present (up arrow).
Repolarization abnormalities occur at potassium levels of 5.5-6.5 mEq/L.
The T waves represent ventricular repolarization, which is why we can see changes to the T waves at these levels.
Left Arrow = Prolonged PR Interval
As potassium levels increase to about 6.5-7.0 mEq/L, PR interval prolongation and P wave widening may be present (left arrow).
Progressive atrial paralysis occurs at potassium levels of 6.5-7.0 mEq/L.
The P waves represent atrial depolarization.
The PR interval represents the duration between the start of the P wave (atrial depolarization) and the start of the QRS complex (ventricular repolarization).
The P wave and PR interval both involve the atria, which is why the progressive atrial paralysis affects the P wave and PR interval morphology.
Down Arrow = Dropped P Waves
As potassium levels approach 7.0 mEq/L, the P waves may disappear on EKG (down arrow).
Atrial paralysis continues to progress at potassium levels of 7.0 mEq/L.
The P waves represent atrial depolarization, which is why the worsening atrial paralysis continues to affect the P waves (dropped P waves).
Right Arrow = Widening QRS
As potassium levels approach 7.0-9.0 mEq/L, widened QRS complexes may be present (right arrow).
Conduction abnormalities occur at potassium levels of 7.0-9.0 mEq/L, which can lead to widened QRS complexes, arrhythmias, heart blocks, etc.
Potassium levels greater than 9.0 mEq/L can eventually lead to sine wave patterns and life threatening arrhythmias such as asystole, ventricular fibrillation, or PEA.
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Referenceshttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC3627796/https://litfl.com/hyperkalaemia-ecg-library/