ECG Waveforms Flashcards

1
Q

what does a single ECG complex comprise of?

A

individual waves and lines that occur in a specific sequence as a result of depolarization and repolarization

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2
Q

isoeletric line

A

the baseline of an ECG tracing

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3
Q

waveform

A

deflection or movement away from the baseline

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4
Q

segment

A

the line between 2 waveforms

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5
Q

interval

A

consists of a waveform and a segment

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6
Q

complex

A

a collection of waveforms ie) QRS complex

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7
Q

what are the components of an ECG?

A

P wave, PR interval, QRS complex, ST segment, T wave, QT interval

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8
Q

in lead II, which electrode is positive and which is negative?

A

LL is positive
RA is negative

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9
Q

what does the P wave represent?

A

atrial depolarization

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10
Q

if the P wave is normal, what would the direction of electrical flow be?

A

from R to L and down toward positive electrode

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11
Q

P Wave
- location
- amplitude
- duration
- configuration
- deflection

A
  • precedes QRS complex
  • 2-3mm high
  • 0.06-0.12 seconds
  • rounded and upright
  • positive and upright in lead II
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12
Q

what does the isoelectric line represent?

A

after atria are depolarized, wave of depolarization continues towards AV node and junctional tissues and there’s a short pause in electrical flow allowing atria to recover and repolarize

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13
Q

isoelectric line location?

A

immediately after P wave

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14
Q

what does the PR interval represent?

A

amount of time it takes for the electrical impulse to leave the SA node, depolarize the atria, and pass through the AV junction

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15
Q

PR interval
- location
- duration
- composed of

A
  • beginning of P wave to beginning of QRS complex
  • 0.12-0.20 seconds
  • composed of P wave and PR segment
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16
Q

what does the Q wave represent?

A
  • delay of electrical activity at AV node
  • after delay, wave of depolarization flows toward bundle of His then to L bundle branch
  • interventricular septum is depolarized from L to R
17
Q

Q wave
- location
- deflection

A
  • after a P wave and PR interval
  • first negative deflection
18
Q

what does the R wave represent?

A

wave of depolarization continues down bundle branches and flows over bulk of ventricular tissue

19
Q

R wave
- location
- deflection

A
  • right after Q wave
  • large upright positive deflection because: electrical current is directed down towards positive electrode and b/c ventricles are depolarizing
20
Q

what does S wave represent? its deflection?

A
  • electrical flow extends up to Purkinje fibers
  • flow of electrical current is away from positive electrode = small negative downwards deflection
21
Q

QRS complex represents?
- location
- duration

A
  • all of ventricular depolarization from endocardium to epicardium
  • follows PR interval
  • 0.10 seconds or less
  • measured to end of S wave
22
Q

what does the ST segment represent?

A

early ventricular repolarization

23
Q

what does the T wave represent?

A
  • atrial repolarization activity is hidden in QRS complex b/c atrial tissue is smaller
  • ventricular repolarization is more visible
  • ventricular tissue recovers or repolarizes from epicardium to endocardium and electrical flow goes toward (+) electrode
24
Q

T wave deflection

A

positive upright

25
Q

QT interval represents? location?

A
  • represents total ventricular activity
  • begins at beginning of QRS complex to end of T wave
26
Q

what happens if Q wave is not visible and you’re measuring QT interval?

A

begin measuring from start of R wave

27
Q

J Point

A
  • junction point where QRS complex and ST segment meet
  • important reference point when analyzing waveform for signs of myocardial ischemia or injury (ST elevation or ST depression)
  • not always a perfect angle
28
Q

what is significant about the P wave and PR interval?

A

P wave signifies atrial depolarization which is important if atria were to contract. atrial depolarization alone does not provide atrial kick. PR interval accounts for atrial depolarization and AV nodal delay to allow for an effective atrial kick

29
Q

what is the most important component of the waveform?

A

QRS complex as it signifies ventricular depolarization. without it, ventricles can’t contract. most essential for CO