Certified Rhythm Analysis Technician (CRAT) Practice Exam

What is a common method to interpret heart rhythm in an ECG?

1. Counting small squares between R-R intervals

2. Assessing QRS width

3. Measuring PR interval

4. Examining T wave morphology

The correct answer is: Counting small squares between R-R intervals

Counting small squares between R-R intervals is an established method to interpret heart rhythm on an ECG. This technique allows practitioners to determine the heart rate and assess the regularity of the rhythm. By counting the number of small squares on the ECG strip between successive R waves (the peaks of the QRS complex), one can calculate the heart rate using the formula: heart rate (beats per minute) = 300 divided by the number of large squares between R-R intervals or by converting the number of small squares directly to time. Understanding the interval between beats is crucial for diagnosing conditions such as bradycardia, tachycardia, or arrhythmias. This method is particularly valuable because it can be used quickly during patient evaluation in acute settings. The other options, while relevant in the context of ECG interpretation, serve different purposes. Assessing QRS width helps in identifying conduction abnormalities, measuring the PR interval is essential for evaluating atrioventricular (AV) conduction, and examining T wave morphology is important for identifying ischemia or electrolyte imbalances. These measures provide additional information about cardiac function but do not focus specifically on the rhythm itself in the same direct way that counting R-R intervals does.