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Cardiovascular > EXAM #1: REVIEW OF ECG > Flashcards

EXAM #1: REVIEW OF ECG Flashcards

1
Q

Where is the Cl- concentration high?

A

Extracellular

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2
Q

Is the cardiac cell negatively charged or positively charged intracellularly?

A

Negative

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3
Q

What are the five phases of the cardiac action potential?

A 
0=  Rapid upstroke/ depolarization 
1=  Early repolarization
2= Plateau 
3= Rapid repolarization
4= Resting membrane potential
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4
Q

Describe the ion flux in phase 0 of the cardiac action potential.

A
  • Rapid influx of Na+
  • FAST Na+ channels

“Rapid depolarization”

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5
Q

Describe the ion flux in phase 1 of the cardiac action potential.

A
  • Na+ channels close
  • Voltage-gated K+ channels OPEN and K+ moves OUT

“Early repoarlization”

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6
Q

Describe the ion flux in phase 2 of the cardiac action potential.

A
  • Slow Ca++ channels open

- Opposing movement of Ca++ IN and K+ out= PLATEAU

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7
Q

Why is the plateau phase of the action potential important?

A

This phase corresponds to systole; the pause allows contraction to occur

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8
Q

Describe the ion flux in phase 3 of the cardiac action potential.

A
  • Ca++ channels close
  • K+ channels are still OPEN
  • K+ OUT

“Rapid repolarization”

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9
Q

Describe the ion flux in phase 4 of the cardiac action potential.

A
  • Na+/K+ ATPase
  • Only K+ channels are open and a SMALL amount of K+ fluxes

“Resting membrane potential”

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10
Q

How many phases are there in the nodal action potential? What are they?

A

Three phases: 0, 3, and 4

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11
Q

What phases are missing from the nodal action potential?

A

1 and 2

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12
Q

How does the resting membrane of the nodal action potential differ from the cardiac myocyte action potential?

A

Cardiac myocyte= -90mV

Nodal= -60 mV

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13
Q

Describe the ion flux in phase 0 of the nodal action potential.

A
  • Upon reaching threshold, Slow Ca++ channels open

- Ca++ INFLUX

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14
Q

Describe the ion flux in phase 3 of the nodal action potential.

A
  • After depolarization, K+ channels open

- K+ EFFLUX

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15
Q

Describe the ion flux in phase 4 of the nodal action potential.

A
  • Funny channels open (HCN)
  • K+ efflux progressively declines
  • Ca++ influx occurs, leading to slow depolarization
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16
Q

Outline the normal sequence of depolarization in the heart.

A

1) SA node
2) Atrial syncitium/ internodal tracts
3) AV node
4) Bundle of His
5) Purkinjie fibers
6) Ventricles

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17
Q

What sequence of depolarization occurs in the ventricles?

A

1) Interventricular septum
2) Apex of the heart
3) Ventricular free walls

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18
Q

What are the two branches of the left bundle branch?

A

Left aterosuperior fasicle

Left posteroinferior fasicle

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19
Q

What is the conduction velocity of the cardiac depolarization in the SA node?

A

Less than 0.01 m/sec

20
Q

What is the conduction velocity of the cardiac depolarization in the atrial myocardium?

A

1.0- 1.2 m/sec

21
Q

What is the conduction velocity of the cardiac depolarization in the AV node?

A

0.02-0.05 m/sec

22
Q

What is the conduction velocity of the cardiac depolarization in the Bundle of His?

A

1.2- 2.0 m/sec

23
Q

What is the conduction velocity of the cardiac depolarization in the bundle branches?

A

2.0- 4.0 m/sec

24
Q

What is the conduction velocity of the cardiac depolarization in the Purkinje fibers?

A

2.0-4.0 m/sec

25
Q

What is the conduction velocity of the cardiac depolarization in the ventricular myocardium?

A

0.3 -1.0 m/sec

26
Q

Where is the conduction velocity the fastest in the heart?

A

Prukinje fibers

27
Q

Where is the conduction velocity the slowest in the heart?

A

AV node

28
Q

What does the p-wave of the ECG represent?

A

Atrial myocyte depolarization

29
Q

What does the PR Interval represent?

A

Time it takes for the stimulus to spread through the atria and pass through the AV junction

30
Q

What is the normal PR interval?

A

0.12- 0.2 seconds i.e. 3-5 small boxes

Note that 1mm = 0.04 sec

31
Q

What does the QRS complex correspond to?

A

Ventricular myocyte depolarization

32
Q

What does the T-wave represent?

A

Ventricular repolarization

33
Q

What does the ST segment represent?

A

Ventricular myocyte plateau

34
Q

What does 10mm or 2x large boxes represent vertically on ECG paper?

A

1 mV

35
Q

What does 7 large boxes between R-waves represent in terms of rate?

A

43 bpm

36
Q

Draw the hexaxial diagram.

A

p. 36, 5-2

37
Q

What does the QT interval correspond to?

A

Entire ventricular action potential

38
Q

How can you specifically determine the mean QRS axis?

A

1) Take biphasic lead
2) 90 degrees from that

OR

1) Average of 2x tallest QRS complexes

39
Q

What is the quick way to determine the mean QRS axis?

A

Looks at leads I, II, and III

40
Q

What does an upward I, II, and III indicate?

A

Normal axis (between -30 and 100)

41
Q

What does an upward I, mid II, and downward III indicate?

A

“Physiologic left-axis deviation”

42
Q

What does upward I and downward II and III indicate?

A

LAD

43
Q

What does down I and upward III indicate?

A

RAD (100+)

44
Q

What does downward I and upward II and III indicate?

A

Extreme axis deviation

45
Q

What are the general steps to interpreting and ECG?

A

1) Rate
2) Rhythm
3) Axis
4) Conduction
5) Infarction

Cardiovascular (38 decks)

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