Which ECG change on telemetry is most characteristic of severe hyperkalemia?

Which ECG change on telemetry is most characteristic of severe hyperkalemia?

• A. Flattened T waves with prominent U waves
• B. Tall, peaked T waves progressing to wide QRS and possibly a sine-wave pattern
• C. ST-segment elevation in leads V2-V4
• D. Prolonged PR interval with widened QRS but no T changes

Answer: (B)

Severe hyperkalemia is best recognized on ECG by tall, peaked T waves that progressively widen the QRS complex and can merge into a sine‑wave pattern. This sequence occurs because high extracellular potassium speeds up repolarization (producing the tall, peaked T waves) while also slowing conduction through the heart as potassium blocks further depolarization, leading to PR prolongation and QRS widening. As potassium rises even more, the QRS widens further and the ECG can take on a sine‑wave appearance, indicating a life‑threatening risk of ventricular arrhythmias or arrest. The other patterns fit different scenarios: flattened T waves with prominent U waves point to hypokalemia; ST‑segment elevation in precordial leads suggests an acute myocardial infarction; and prolonged PR with widened QRS but no T changes can occur earlier but does not capture the severe, sine‑wave stage seen with extreme hyperkalemia.

Severe hyperkalemia is best recognized on ECG by tall, peaked T waves that progressively widen the QRS complex and can merge into a sine‑wave pattern. This sequence occurs because high extracellular potassium speeds up repolarization (producing the tall, peaked T waves) while also slowing conduction through the heart as potassium blocks further depolarization, leading to PR prolongation and QRS widening. As potassium rises even more, the QRS widens further and the ECG can take on a sine‑wave appearance, indicating a life‑threatening risk of ventricular arrhythmias or arrest.

The other patterns fit different scenarios: flattened T waves with prominent U waves point to hypokalemia; ST‑segment elevation in precordial leads suggests an acute myocardial infarction; and prolonged PR with widened QRS but no T changes can occur earlier but does not capture the severe, sine‑wave stage seen with extreme hyperkalemia.