Cardiac Medicine Certification Practice Exam 2026 – Comprehensive Prep Guide

Question: 1 / 400

How is the QT interval measured on an ECG?

From the P wave to the QRS complex

From the Q wave to the end of the T wave

The QT interval on an ECG is measured from the beginning of the Q wave to the end of the T wave. This interval represents the total time taken for the heart's ventricles to depolarize and then repolarize. It is an important measure as it reflects the duration of ventricular electrical activity. Prolongation of the QT interval can be associated with an increased risk of arrhythmias, so understanding its accurate measurement is crucial for assessing cardiac health.

The other options do not correctly define the QT interval. The interval does not start from the P wave or end at the S wave, and measuring it from those points would not capture the full span of ventricular activity reflected in the Q and T waves. Each of these mistakenly focuses on other components of the ECG, which could lead to misunderstanding the timing of ventricular repolarization in relation to depolarization.

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From the start of the T wave to the end of the S wave

From the beginning of the P wave to the end of the R wave

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