Waveforms, segments, and intervals Flashcards

1
Q

State which electrophysiological event corresponds to the P-wave, QRS complex, T-wave, and U-wave

A
  • P: Atrial depolarization
  • QRS: Ventricular Depolarization
  • T: Ventricular repolarization
  • U: Unknown
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2
Q

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

A

Left Atrial Enlargement

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3
Q

Define the boundaries of the PR segment

A

end of P-wave to beginning of QRS complex

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4
Q

Define the TP segment and explain its significance to ECG interpretation

A
  • 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
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5
Q

PR depression may be a sign of

A

pericarditis

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6
Q

Define an interval with relation to ECGs

A

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

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7
Q

What are the endpoints of the PR interval?

A

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

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8
Q

Define the QT interval.

A

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

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9
Q

What property of ECGs do intervals describe?

A

Duration (not amplitude!)

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10
Q

What is the normal duration of the PR interval?

A

120-200ms (3-5 small squares)

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11
Q

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

A
  • 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.
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12
Q

What is the normal duration of the QRS interval?

A

<120ms (3 small squares)

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13
Q

What is indicated by a QRS duration >120ms?

A

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

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14
Q

A quick approximation for an appropriate QT interval is:

A

no more than 1/2 the RR interval

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15
Q

Factors that influence appropriate QT duration are:

A

Age, sex, heart rate

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16
Q

What is indicated by a prolonged QT interval?

A

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

17
Q

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

A
  • PR: 120-200ms
  • QRS: <120ms
  • QT: <1/2 RR
18
Q

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

A

Junction.

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

19
Q

What is the Bazzett formula for QTc?

A

QTc= QT / √ RR

20
Q

What are normal QTc intervals for men and women?

A
  • 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