Which intervals or segments are commonly measured on an ECG?

• A. PR, ST segment, QT
• B. PR interval only
• C. QT only
• D. PR, QT only

Answer: (A)

Measuring ECG features focuses on how the heart’s electrical impulse travels, how the ventricles activate and recover, and whether there are signs of ischemia. The PR interval shows the time from atrial activation to the start of ventricular activation, reflecting AV conduction. The ST segment is the flat part after the QRS that helps detect ischemia or injury when it deviates from baseline. The QT interval covers the entire period of ventricular depolarization and repolarization, and its length relates to arrhythmic risk. Since routine interpretation uses all three to assess conduction timing, ventricular activity, and potential ischemia, including PR interval, ST segment, and QT interval provides the most complete and commonly used set. The other options omit one of these essential aspects, making them incomplete.