define normal qrs interval
Related to QRS interval: QT interval. the duration of the QRS complex in the electrocardiogram. In the electrocardiogram, the interval that denotes depolarization of the ventricles, between the beginning of the Q wave and the end of the S wave. Its normal duration is 120â200 msec. Shorter durations are found, e.g., in preexcitation. Longer durations are indicative of first-degree heart block.