Certified Rhythm Analysis Technician (CRAT) Practice Exam 2025 - Free CRAT Practice Questions and Study Guide

The most common paper speed used for a standard electrocardiogram (ECG) is 25.0 mm/sec. This speed allows for the optimal representation of the heart's electrical activity, making it easier to analyze the waveforms and intervals, which are crucial for diagnostic purposes.

When the paper speed is set at 25.0 mm/sec, each small square on the ECG paper represents 0.04 seconds (or 40 milliseconds), while a larger square (composed of five small squares) represents 0.20 seconds (or 200 milliseconds). This scale is widely accepted and allows clinicians to measure intervals, such as PR, QRS, and QT intervals, accurately and effectively.

The other options provided do not represent the standard practice for ECG paper speed. A speed of 12.5 mm/sec would reduce the clarity of the waveforms, while 50.0 mm/sec and 100.0 mm/sec would increase the speed at which the heart's electrical activity is recorded, potentially compressing data and making it difficult to interpret the results accurately. Thus, the choice of 25.0 mm/sec aligns with the conventions established in clinical practice for routine ECGs, ensuring proper assessment of cardiac function.