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Flashcards in Waveforms, segments, and intervals Deck (20)
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State which electrophysiological event corresponds to the P-wave, QRS complex, T-wave, and U-wave

  • P: Atrial depolarization
  • QRS: Ventricular Depolarization
  • T: Ventricular repolarization
  • U: Unknown


An unusually long P-wave may be a sign of ______

Left Atrial Enlargement


Define the boundaries of the PR segment

end of P-wave to beginning of QRS complex


Define the TP segment and explain its significance to ECG interpretation

  • Segment running from the end of one T-wave to the beginning of the next P-wave
  • Least likely part of ECG to be affected by pathology so serves as a reference for establishing a baseline


PR depression may be a sign of



Define an interval with relation to ECGs

intervals contain one or more waveforms +/- one or more segments


What are the endpoints of the PR interval?

beginning of P-wave to beginning of QRS complex (P-wave + PR segment)


Define the QT interval.

sum of the duration of the QRS complex, ST segement, and T-wave (beginning of QRS to end of T-wave)


What property of ECGs do intervals describe?

Duration (not amplitude!)


What is the normal duration of the PR interval?

120-200ms (3-5 small squares)


What is indicated by a shortened or prolonged PR interval? Define what is meant by shortened or prolonged PR.

  • Shortened (<120ms or 3 small squares): indicates an abnormal pathway for conduction from atria to ventricles (as in LGL or WPW)
  • Prolonged (>200ms or 5 small squares): indicates delayed AV conduction as in AV nodal block.


What is the normal duration of the QRS interval?

<120ms (3 small squares)


What is indicated by a QRS duration >120ms?

abnormal sequence of ventricular depolarization (as in BBB) or excessive ventricular mass (LVH)


A quick approximation for an appropriate QT interval is:

no more than 1/2 the RR interval


Factors that influence appropriate QT duration are:

Age, sex, heart rate


What is indicated by a prolonged QT interval?

a QT interval that is >1/2 the RR interval indicates prolonged ventricular depolarization (long QT), which may indicate ischemia or predispose to torsades des pointes


List appropriate durations for the PR, QRS, and QT intervals

  • PR: 120-200ms
  • QRS: <120ms
  • QT: <1/2 RR


The "J" in J-point stand for ________. The J point is defined as


The J point indicates where the QRS complex meets the ST segment


What is the Bazzett formula for QTc?

QTc= QT / √ RR


What are normal QTc intervals for men and women?

  • QTc is prolonged if > 440ms in men or > 460ms in women
  • QTc > 500 is associated with increased risk of torsades de pointes
  • QTc is abnormally short if < 350ms