EKG Basics Flashcards

1
Q

The vertical axis of an EKG strip measures?

A

measure voltage in millimeters (mm) or Millivolts (mV)

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2
Q

The horizontal axis of an EKG strip measures?

A

measures units of time in milliseconds

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3
Q

Each vertical small box of an EKG represents how many mm/mV?

A

1 mm or 0.1 mV

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4
Q

Each horizontal small box of an EKG represents how much time?

A

40 milliseconds (msec) or .04 sec

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5
Q

What is the lead marker on an EKG strip?

A

straight vertical line that indicates every 3 seconds

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6
Q

What is the standardization bar on an EKG strip?

A

Found on the fore most left of the strip and indicates the EKG machine is properly calibrated

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7
Q

Specifications of the standardization bar indicating the EKG machine is properly calibrated?

A
  • 10 mm tall or 2 large squares high

- 0.20 sec or 1 large square wide

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8
Q

Each vertical large box of an EKG represents how many mm/mV?

A

5 mm/0.5 mV or 5 small boxes

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9
Q

Each horizontal large box of an EKG represents how many msecs?

A

0.20 secs or 200 milliseconds

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10
Q

The limb leads of an EKG shows the activity of which part of the heart?

A

the frontal plane, from top to bottom

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11
Q

Which EKG leads are limb leads?

A
  • I, II, III
  • aVR, aVL, aVF
  • are bipolar leads
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12
Q

The precordial or chest leads of an EKG show which the activity of which part of the heart?

A

activity of the horizontal plane from front to back

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13
Q

Which EKG leads are precordial or chest leads?

A

V-leads (V1 - V6)

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14
Q

What is the Isoelectric line on an EKG?

A

Baseline of an EKG and is the straight line before the the p-wave

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15
Q

What is the J-Point of an EKG?

A

The point marking the end of the QRS complex and the beginning of the ST segment at the isoelectric line

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16
Q

Sections of the heart that are depolarized by slow calcium channels?

A

SA and AV nodes

17
Q

Sections of the heart that are depolarized by fast sodium channels?

A
  • Bundle of His/Purkinje fibers
  • atrial muscle
  • ventricular muscle
18
Q

What happens during Phase 0 of a fast channel (Na+) depolarization cycle?

A

initiates the action potential through rapid depolarization with Na+ influx into cell

19
Q

What happens during Phase 1 of a fast channel (Na+) depolarization cycle?

A

Partial repolarization due to K+ leaving cell through iK1 channels

20
Q

What happens during Phase 2 of a fast channel (Na+) depolarization cycle?

A

Membrane potential plateau – calcium enters cell and promotes contraction of muscle (K+ efflux continues)

21
Q

What happens during Phase 3 of a fast channel (Na+) depolarization cycle?

A
  • Rapid repolarization

- Na+ out and K+ in

22
Q

What happens during Phase 4 of a fast channel (Na+) depolarization cycle?

A
  • Membrane potential stable

- cell is in a polarized state and ready for depolarization

23
Q

What happens to cardiac cells if no stimulus is received?

A

They will depolarize by themselves due to the eventual influx of Na+

24
Q

Where are the cardiace pacer cells located?

A

SA and AV node

25
Q

What happens during Phase 0 of a slow channel (Ca++) depolarization cycle?

A

slow depolarization due to slow influx of Ca++

26
Q

What action do epi and NE have on cardiac Ca++ channels?

A

Epi and NE stimulate B1 receptors, opening Ca++ channels; sympathetic response that increase the HR

27
Q

What action does acetylcholine have on cardiac Ca++ channels?

A

acetylcholine stimulates the vagus nerve, preventing the opening of the Ca++ channels; parasympathetic response that slows the HR

28
Q

What happens during Phase 1 of a slow channel (Ca++) depolarization cycle?

A

there is no phase 1 or rapid depolarization of the Ca++ channels

29
Q

What happens during Phases 2 & 3 of a slow channel (Ca++) depolarization cycle?

A

Slow repolarization as Ca++ is pumped out of the cell

30
Q

What is the normal vector/direction for Lead I?

A

RA to LA

31
Q

What is the normal vector/direction for Lead II?

A

RA to RL

32
Q

What is the normal vector/direction for Lead III?

A

LA to LL

33
Q

Which leads are known as the limb leads?

A

aVR, aVF, aVL

34
Q

Which leads are known as the precordial leads?

A

V1-V6

35
Q

What is a normal QRS duration?

A

80-100 ms

36
Q

What is a normal P-R interval?

A

120-200 ms

37
Q

What is a normal QT interval?

A

400-440 ms

38
Q

What is a normal QTc for males?

A

< 420 ms

39
Q

What is a normal QTc for females?

A

< 440 ms