Which statement best describes hyperkalemia's effect on the heart in severe cases?

Which statement best describes hyperkalemia's effect on the heart in severe cases?

• A. ST segment elevation
• B. Peaked T waves that may progress to QRS widening
• C. Decreased heart rate only
• D. No ECG changes until potassium is extremely high

Answer: (B)

Hyperkalemia alters cardiac conduction by increasing extracellular potassium, which makes the resting membrane potential less negative and partially inactivates sodium channels. This slows conduction and changes the timing of ventricular depolarization and repolarization. The earliest and most recognizable ECG change is tall, peaked T waves from faster repolarization. As potassium rises further, the PR interval lengthens and the QRS complex widens due to slowed ventricular conduction. In severe cases, this progression can culminate in dangerous rhythms or a sine-wave pattern, reflecting major conduction collapse and impending arrest. So, peaked T waves that may progress to QRS widening best describe the ECG changes seen in severe hyperkalemia. ST segment elevation isn’t typical of hyperkalemia (it’s more associated with acute myocardial injury), symptoms aren’t limited to decreased heart rate, and ECG changes do not wait until potassium is extremely high.

Hyperkalemia alters cardiac conduction by increasing extracellular potassium, which makes the resting membrane potential less negative and partially inactivates sodium channels. This slows conduction and changes the timing of ventricular depolarization and repolarization. The earliest and most recognizable ECG change is tall, peaked T waves from faster repolarization. As potassium rises further, the PR interval lengthens and the QRS complex widens due to slowed ventricular conduction. In severe cases, this progression can culminate in dangerous rhythms or a sine-wave pattern, reflecting major conduction collapse and impending arrest.

So, peaked T waves that may progress to QRS widening best describe the ECG changes seen in severe hyperkalemia. ST segment elevation isn’t typical of hyperkalemia (it’s more associated with acute myocardial injury), symptoms aren’t limited to decreased heart rate, and ECG changes do not wait until potassium is extremely high.