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Cardiology > EKG-Session 1 > Flashcards

EKG-Session 1 Flashcards

1
Q

Contractility

A

ability of heart muscle fibers to shorten, generate force, and pump blood

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2
Q

Automaticity

A

ability of heart tissue to independently and rhythmically generate electrical impulses

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3
Q

Conductivity

A

distribution of electrical impulses throughout the heart via a conduction system

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4
Q

Excitability (irritability)

A

ability of cardiac cells to respond to external stimuli: chemical, mechanical, or electrical

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5
Q

Polarized (resting) state

A

Interior of the myocyte is negatively charged

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6
Q

Depolarization

A

Interior of the myocyte becomes positive
Influx of Na+ ions
Results in myocardial contraction

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7
Q

Repolarization

A

Recovery phase
Interior of the myocyte returns to negative charge
Accomplished by transfer of potassium (K+) ions out of the myocytes

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8
Q

What is an absolute refractory period?

A
  • QRS to peak of T wave

- Myocardial cell will NOT respond to further stimulation

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9
Q

What is relative refractory period?

A
  • Downslope of T wave

- Some cardiac cells depolarized; can be stimulated to depolarize with a stronger-than-normal stimulus

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10
Q

What is a supernormal period?

A

Weaker-than-normal stimulus can depolarize

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11
Q

Explain the principle of automaticity.

A

Each structure within the conduction system:

  • Conducts electrical activity at a specific velocity
  • Can initiate electrical activity independently at a characteristic discharge rate
  • Under appropriate conditions, each structure could act as a pacemaker
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12
Q

Explain the concept of Overdrive suppression

A

Suppression of the automaticity and independent depolarization of cells with pacemaker potential by tissues firing at a higher intrinsic rate of automaticity.

Overdrive suppression explains why the SA node normally functions as the pacemaker of the heart, despite the presence of other tissues with automaticity

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13
Q

What is the inherent rate of spontaneous depolarization of the Sino-Atrial (SA) node?

A

60-100min

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14
Q

What is the inherent rate of spontaneous depolarization of the Atrial Cells?

A

60-75/min

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15
Q

What is the inherent rate of spontaneous depolarization of the Atrioventricular node?

A

40-60/min

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16
Q

What is the inherent rate of spontaneous depolarization of the Ventricular cells?

A

30-45/min

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17
Q

What does the horizontal axis of an EKG record?

A

time

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18
Q

What does the vertical axis of an EKG record?

A

voltage/velocity

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19
Q

Fast response cardiac action potentials work through what type of channels?

A

Sodium

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20
Q

Slow response cardiac action potentials work via what types of channels?

A

Calcium

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21
Q

Where in the heart do slow response cardiac action potentials occur?

A

SA and AV nodes

22
Q

Where in the heart do fast response cardiac action potentials occur?

A

normal myocardial fibers in atria, ventricles, and Purkinje fibers

23
Q

Describe ‘positive deflections’ with regards to measuring velocity on an EKG.

A

Record impulse moving toward positive electrode

Deflections above the baseline

24
Q

Describe ‘negative deflections’ with regards to measuring velocity on an EKG.

A

Record impulse moving away from positive electrode

Deflections below the baseline

25
Q

How many limb leads are there?

A

6

26
Q

List the 3 bipolar leads

A

Lead I, II, III

27
Q

List the 3 Augmented limb leads

A

Lead aVR-Augmented voltage (right)
Lead aVL-Augmented voltage (left)
Lead aVF-Augmented voltage (foot)

28
Q

Describe chest lead placement for V1

A

4th intercostal space, right sternal border

29
Q

Describe chest lead placement for V2

A

4th intercostal space, left sternal border

30
Q

Describe chest lead placement for V3

A

Midway between V2 and V4

31
Q

Describe chest lead placement for V4

A

5th left intercostal space, mid-clavicular line

32
Q

Describe chest lead placement for V5

A

Midway between V4 and V6

33
Q

Describe chest lead placement for V6

A

5th left intercostal space, mid-axillary line

34
Q

Atrial depolarization

A

Represented by P wave on EKG strip
Results in atrial contraction
(SA node firing, wave spreading through atrium, results in atrial contraction)

35
Q

Atrial repolarization

A

Lost in QRS complex on EKG strip

36
Q

QRS Complex

A

Ventricular depolarization

(Impulse travels from AV node through bundle branches and Purkinje fibers, Results in ventricular contraction

37
Q

Q Wave

A

First negative deflection after the P wave

38
Q

R Wave

A

First positive deflection after the P wave

39
Q

S Wave

A

Negative deflection after an R wave

40
Q

T Wave

A 
Electrical deflection following QRS complex
Normally positive (upward)
-Represents the rapid phase of ventricular depolarization
41
Q

U Wave

A

Follows T wave
-Perkinje repolarization
-Usually NOT present
May indicate clinically relevant pathology (HYPOKALEMIA)

42
Q

What does the PR Segment represent?

A

Isoelectric (at the baseline)
End of P wave to beginning of QRS complex

Represents delay of electrical impulse through the AV node (allows time for ventricles to fill with blood)

43
Q

Where does the PR Interval occur on an EKG strip and what does it represent?

A

located from the beginning of P wave to beginning of QRS complex

Represents atrial contraction and AV node delay

Intervals are horizontal lines and therefore measurements of TIME or DURATION

44
Q

What is the normal duration of a PR Interval?

A

0.12-0.20 seconds
Less than 5 small boxes/less than 1 big box
Varies with heart rate

45
Q

Where does the QRS interval occur on an EKG strip and what does it represent?

A

Beginning of Q to end of S

Represents ventricular depolarization
Very Rapid

46
Q

What is the normal duration of a QRS interval?

A

Less than or equal to 0.12 seconds (3 small boxes)

47
Q

Where does the ST segment occur on an EKG strip and what does it represent?

A

From the end of the QRS to the start of the T wave

Represents initial phase of ventricular repolarization

Normally isoelectric

Elevation or depression often clinically significant

48
Q

Where does the QT Interval occur on an EKG strip and what does it represent?

A

From the start of the QRS complex to the end of the T wave

Represents ventricular depolarization/repolarization

49
Q

What is the normal duration of a QT interval?

A

Should be 0.30-0.44 seconds
Should be less than half of the R-R interval
Corrected for rate (QTc)

50
Q

Where does the R-R interval occur on an EKG strip and what is its significance?

A

Distance from one QRS complex to next

Used to calculate rate

Cardiology (8 decks)

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