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PA: Exam 2 > 7.7 EKG > Flashcards

7.7 EKG Flashcards

1
Q

Firing Rates:
SA
AV
Bundle of His

A

SA: 60-100 action potentials per minute
AV: 40-60 beats per minute
20-40 per minute

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2
Q

Where do you see the SA node electrical activity on EKG?

A

You don’t! It’s very small.

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3
Q

P Wave

A

Depolarization, contraction of both atria

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4
Q

Ventricular Depolarization

A

QRS Complex

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5
Q

Ventricular Contraction on an EKG

A

Begins with the QRS, ends with the T

Spans depolarization and repolarization

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6
Q

What does a long QT interval indicate?

A

Warns that the patient is vulnerable to irregular rhythms

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7
Q

Normal intervals of:

  • PR
  • QRS
  • QT
A

PR: <0.4 seconds

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8
Q

What is the purpose of limb leads?

A

Record the activity in the coronal or frontal plane of the body

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9
Q

How do limb leads work? What type of configuration?

A
  • Bipolar configurations
  • One positive pole electrode and one negative pole electrode such as leads I, II and III.
  • Energy moves from the negative electrode toward the positive electrode.
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10
Q

What is the purpose of chest leads?

A

Record activity in the axial (horizontal) plane of the body

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11
Q

Where are chest leads placed?

A 
V1&2: 4th ICS, either side of sternum
V4: 5th ICS MCL
V3: Between V2 and V4
V6: 5th ICS: Mitral area
V5: 5th ICS between V4 and V6
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12
Q

Meaning of positively deflected v negatively deflected

A
  • Electrical activity moving from negative electrode to positive electrode = positively deflected
  • Electrical activity moving away from positive electrode = negatively deflected
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13
Q

ECG paper: How fast does it roll out?

A

25mm or 1” per second

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14
Q

How large is each small square on ECG graph paper? How much time does this represent?

A

1mm, 0.04 seconds

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15
Q

On ECG paper, each large box is made up of how many small boxes? Each large box represents how much time?

A

five small boxes, representing 0.20 seconds.

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16
Q

Regular heart rate
Bradycardia
Tachycardia

A

Regular: 60-100

Bradycardia 100

17
Q

How do you calculate rate?

What numbers do you need to know to do this (6)?

A

Count R-R interval and large boxes.

300 - 150 - 100 - 75 - 60 - 50

18
Q

What is heart rhythm?

A
  • The quality of timing as one heart beat is compared to the next, regardless of rate
  • Determined by comparing the length of several adjacent R-R intervals
19
Q

If all R-R intervals are of equal length, you would say that the rhythm is _____

A

REGULAR

20
Q

If R-R intervals are of different lengths but there’s an overall pattern pressent

A

Regularly irregular

21
Q

If there is no overall R-R pattern

A

Irregularly Irregular

22
Q

What causes a premature atrial beat?

A

Atrial focci becomes irritable.

  • Due to sympathetic stimulation (adrenergic substances like adrenaline)
  • Beta 1 receptor stimulants (Caffeine, cocaine, amphetamines, excess digitalis, hyperthyroidism
23
Q

Two things to note about the ECG when observing a premature atrial beat.

A
  • The pause following the PAC is longer than the normal P-P interval, but shorter than twice the normal P-P interval.
  • Note the different shape of the P-P wave.
24
Q

What happens during atrial flutter? (2)

A

In atrial flutter, a single strong ectopic focus in an atria start to beat fast (240-360 beats per minute)
**The AV node acts as the gatekeeper, blocking some of the impulses to the ventricles.

25
Q

What happens during atrial fibrillation? (3)

A
  • Many weak ectopic foci in the atria beat in an uncoordinated pattern, resulting in an uneven baseline of many tiny P waves.
  • Eventually, the ventricles recieve enough electrical stimulation to contract, or contract on their own.
  • IRREGULARLY IRREGULAR.
26
Q

Supraventricular Tachycardia

  • What happens?
  • What’s the HR?
A
  • Occurs when there is a fast, strong stimulus from an ectopic focus above the ventricles but below the SA node, and the heart conducts every beat.
  • HR is 150-250 per minute
27
Q

Premature ventricular contractions

A
  • Ventricular focus can be made irritable by low O2 and low potassium
  • Irritable ventricular focus causes a premature ventricular contraction (PVC), which originates suddenly and produces a giant ventricular complex on the EKG.
28
Q

What are some things that can cause low O2? (6)

A

Airway obstruction, absence of air, low O2 content, reduced cardiac output, poor to absent coronary blood supply due to infarction or insufficiency.

29
Q

What causes ventricular tachycardia?

A

One strong ventricular ectopic focus that hijacks the conduction system of the heart (not sustainable)

30
Q

What is ventricular fibrilation?

A

The beating of many weak ectopic foci in the ventricles, resulting in uncoordinated contractions.

(Cannot circulate blood, not compatible with life.)

31
Q

Four Conduction Abnormalitites

A

1) First-degree Atrioventricular Block
2) Second-degree Atrioventricular Block, Type I
3) Second-degree Atrioventricular Block, Type II
4) Third-degree Atrioventricular Block

32
Q

A First-degree Atrioventricular Block does what to the ECG reading?

A

Makes the PR interval >0.20

33
Q

What happens with a First degree AV Block?

A
  • The impulse within the AV node is delayed, making a longer-than normal pause before ventricular stimulation (PR interval > 0.20)
  • Prolongation consistent with each cycle
34
Q

What happens with a second degree AV block (Mobitz Type I Wenckebach)

A

Progressively longer PR duration until non-conducted PR

going, going, gone

35
Q

What happens with a second degree AV block (Mobitz Type II Wenckebach)

A
  • Consistently normal PR interval, but then a normal punctual P wave with no QRS response
  • Can be a 2:1 or 3:1 mobitz block (happens every 2 or 3 P Waves)
36
Q

What happens with a complete / 3rd degree block

A

No relationship between the P Waves and the QRS complexes (AV node is completely blocked)

37
Q

Sympathetic / Norepinephrine:

  • Activate what kind of receptors
  • What response occurs (3?)
A

B1 adrenergic receptors in the heart

Elicit an excitatory response:

  • Increase SA node-pacing
  • Increase force of myocardial contraction
  • Constricts arteries – increases BP
38
Q

Parasympathetic / acetylcholine:

  • Activate what kind of receptors
  • What response occurs (3)?
A

Cholinergic receptors

Inhibitory effect:

  • Decrease SA node pacing
  • Decrease force of contraction
  • Dilates arteries – decreases BP 35

PA: Exam 2 (10 decks)

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