**Core Concept**
Hyperkalemia is a condition characterized by elevated serum potassium levels, which can lead to cardiac arrhythmias and even cardiac arrest. The ECG changes in hyperkalemia are a result of the effect of potassium ions on the cardiac membrane potential.

**Why the Correct Answer is Right**
The ECG changes in hyperkalemia are a result of the effect of potassium ions on the cardiac membrane potential. As potassium levels rise, the resting membrane potential becomes less negative, and the action potential duration is prolonged. This can lead to a range of ECG changes, including peaked T waves, a prolonged PR interval, and eventually, a sine wave pattern or ventricular fibrillation. The mechanism involves the blockage of sodium channels and the activation of potassium channels in the cardiac membrane.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not describe a characteristic ECG change in hyperkalemia.
**Option B:** This option is incorrect as it describes a characteristic ECG change in hypokalemia, not hyperkalemia.
**Option C:** This option is incorrect as it describes a characteristic ECG change in ischemia, not hyperkalemia.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the ECG changes in hyperkalemia as they can be a life-threatening emergency. The "ramp" sign, which refers to the progressive widening of the QRS complex, is a characteristic feature of hyperkalemia and should prompt immediate treatment.

**Correct Answer:** A. Peaked T waves