thaler chapter 1

1   The Basics

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The QT interval includes the QRS complex, the ST segment, and the T wave. It therefore measures the time from the beginning of ventricular depolarization to the end of ventricular repolarization. And, yes, the term QT interval is used even if a particular QRS complex does not have a Q wave. The term QRS interval is used to describe the duration of the QRS complex alone without any connecting segments. Obviously, it measures the duration of ventricular depolarization.

QRS interval

ST segment

QT interval