The ECG in hyperkalemia classically shows: September 2009, 2010
**Core Concept**
Hyperkalemia is a condition characterized by elevated potassium levels in the blood. It can lead to cardiac arrhythmias and even cardiac arrest. The ECG changes in hyperkalemia are a key diagnostic feature and can be life-saving.
**Why the Correct Answer is Right**
In hyperkalemia, the ECG shows characteristic changes due to the effect of potassium on the cardiac membrane potential. The initial changes include peaked T waves, which are a result of the increased potassium levels affecting the repolarization phase of the cardiac action potential. As potassium levels rise further, the PR interval prolongs, followed by a widening of the QRS complex, and eventually, a sine wave pattern or a flatline ECG. This is due to the depolarization of the cardiac fibers, leading to a loss of the normal cardiac rhythm.
**Why Each Wrong Option is Incorrect**
**Option A:** Prolonged QT interval - This is incorrect because the QT interval shortens in hyperkalemia, not prolongs.
**Option B:** Low voltage QRS complex - This is incorrect because the QRS complex widens in hyperkalemia, not becomes low voltage.
**Option C:** Right axis deviation - This is incorrect because hyperkalemia does not specifically lead to right axis deviation.
**Clinical Pearl / High-Yield Fact**
In hyperkalemia, the ECG changes can be remembered using the mnemonic "PEAKS": Peaked T waves, Elevation of the PR interval, A widening of the QRS complex, and eventually, a Sine wave pattern or a flatline ECG.
**Correct Answer: A. Peaked T waves**