Which factor can alter the measured heart rate on an ECG?

• A. Artifact
• B. Heart Rate Variability
• C. QRS Duration
• D. T Wave Amplitude

Answer: (A)

Measuring heart rate on an ECG relies on accurately detecting the R waves and calculating the interval between them. Any distortion that affects the visibility or timing of these peaks can throw off the rate reading. Artifact from movement, loose leads, muscle activity, or electrical interference can create extra spikes or obscure real R waves, leading to an incorrect counting of beats per minute.

The other factors don’t typically disrupt rate calculation in the same way. Heart rate variability is the natural fluctuation in intervals between beats, which describes how the rate changes over time rather than contaminating the trace. QRS duration affects how long a single beat’s depolarization lasts, not how many beats occur in a minute. T wave amplitude changes the size of the repolarization wave, not the counting of beats.