In hyperkalemia, which ECG change represents a late stage?

In hyperkalemia, which ECG change represents a late stage?

• A. Increased P wave amplitude
• B. Shortened PR interval
• C. Narrow QRS
• D. Progression to sine waves

Answer: (D)

In hyperkalemia, the ECG changes reflect progressively impaired cardiac conduction as potassium rises. Early on, you see tall, peaked T waves from faster repolarization. As potassium increases further, conduction through the atrioventricular node slows, so the PR interval becomes longer and P waves may flatten. The QRS complex also widens because ventricular depolarization slows as extracellular potassium continues to rise. When potassium is severely elevated, the QRS and T waves merge into a sine-wave pattern, a dangerous late stage that signals imminent complete heart block or ventricular arrhythmias. So, the late, ominous change is progression to sine waves. The other options are not characteristic late findings: increased P wave amplitude would not be expected (P waves tend to flatten or disappear with advancing hyperkalemia), a shortened PR interval is not typical (PR tends to prolong), and a narrow QRS is not seen as hyperkalemia worsens (QRS widens).

In hyperkalemia, the ECG changes reflect progressively impaired cardiac conduction as potassium rises. Early on, you see tall, peaked T waves from faster repolarization. As potassium increases further, conduction through the atrioventricular node slows, so the PR interval becomes longer and P waves may flatten. The QRS complex also widens because ventricular depolarization slows as extracellular potassium continues to rise. When potassium is severely elevated, the QRS and T waves merge into a sine-wave pattern, a dangerous late stage that signals imminent complete heart block or ventricular arrhythmias.

So, the late, ominous change is progression to sine waves. The other options are not characteristic late findings: increased P wave amplitude would not be expected (P waves tend to flatten or disappear with advancing hyperkalemia), a shortened PR interval is not typical (PR tends to prolong), and a narrow QRS is not seen as hyperkalemia worsens (QRS widens).