Which combination of findings is evaluated during rhythm assessment to identify abnormalities?

• A. P waves and PR intervals only
• B. QRS duration alone
• C. Premature beats or elevated/depressed ST segments
• D. Heart rate alone

Answer: (C)

Rhythm assessment looks for patterns that deviate from a normal, regular heartbeat by examining both when the beats occur and what the electrical signals look like. The most informative clues to an abnormal rhythm are premature beats and ST segment changes. Premature beats indicate ectopic activity: an atrial or ventricular impulse lands early, disrupting the regular timing of the rhythm. ST segment elevations or depressions signal ischemia or injury that can accompany rhythm disturbances and alter the overall electrical profile of the tracing. If you only check the P waves and PR intervals, you might miss irregular timing; if you focus on QRS duration alone, you miss rhythm irregularities; and looking at heart rate alone tells you how fast the heart is beating but not whether the rhythm is regular or abnormal. So, recognizing premature beats and ST segment changes gives the clearest indication of rhythm abnormalities.