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407 > Lab 1 - ECG > Flashcards

Lab 1 - ECG Flashcards

1
Q

What is electrocardiography?

A

Technique for recording changes in electrical potential associated w/depolarization + repolarization of myocardium

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2
Q

What are the 3 potential applications of ECG?*

A
  1. To determine HR more accurately than by pulse counting (+ provide record of HR which can be rechecked after measurement made)
  2. To watch for abnormal heart rhythms e.g. minimize risk to patient/subject during exercise stress test
  3. Aid in diagnosis (by cardiologist) of heart conditions e.g. myocardial ischemia, myocardial infarction
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3
Q

When does the wave of depolarization begin? How does the spread

A

Begins in SA node (“pacemaker”), then spreads across atria, then through specialized conducting system to ventricles, eventually spreads across ventricles

Wave of depolariztion + repolarization of myocardium spread from heart thruout body

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4
Q

Why does human tissue conduct electric current well?

A

Cause of water + electrolyte content of body

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5
Q

Is it possible to sense the electric potentials at the surface of skin? If so, how?

A

Yes but the electric signal at surface of skin has small amplitude (~1mV) so special equipment required to detect signals aka ELECTROCARDIOGRAPH which detects, amplifies, and displays signals; ELECTROCARDIOGRAM is the tracing

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6
Q

What is the fxn of transducer?

A

Sense physical phenomena and produce electrical signal

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7
Q

Whats an electrode*

A

Type of transducer which changes IONIC into ELECTRIC current

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8
Q

How do electrodes fxn?

A
  • behave like miniature electrochemical batteries
  • generate own DC voltage on which cardiac electric signals are superimposed + transmitted to ECG
  • ECG electrode must be designed so provides relatively low + stable impedance when placed on skin
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9
Q

Pros of electrodes

A

Inexpensive to make, conveniently manipulated by practitioner

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10
Q

What is the fxn of the gel component of the electrode pair

A

Hydrate skin, lowering electrode-skin impedance

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11
Q

Ways to lower electrode-skin impedance?

A

Inc skin contract area of conductive surface

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12
Q

What can happen is the electrode doesn’t provide stable interface btwn gel and skin

A

Wandering baseline, or excessive electrical interference, and/or unusually large muscle artifact during recording

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13
Q

Where do flat plate electrodes go

A

Secured to wrists and ankles w/straps

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14
Q

Where do suction cups go

A

Applied to chest

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15
Q

How do disposable floating electrodes differ

A
  • Have adhesive surface protected by a peel-off backing (better at holding in place)
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16
Q

Describe the steps of good skin prep

A
  • Skin at sites where electrodes r to b applied rubbed w/lipid solvent e.g. ethanol, to remove skin oil
  • If hairy, site should be shaved
  • Analogous to stripping plastic insulation from electric wire to inc electrical conductivity
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17
Q

What is electrode paste/jelly and its fxn

A

Aqueous suspension of electrolytes, ensures good electrical continuity between electrode + skin

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18
Q

Fxn of reference electrode aka ground electrode?

A
  • Improves quality of tracing
  • allows ECG (machine) to identify + eliminate electrical “noise” found over large region of body
  • also used in EMG (electromyography)
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19
Q

Two fxns of grounding

A
  • PREVENTS ELECTRIC SHOCK to subject or operator. Provides LOW RESISTANCE PATHWAY TO EARTH (“ground”) for current which can reach outer case of ECG machine due to a fault
  • If nerves/muscles electrically stimulated from surface, current from stimulus travels not only to tissues but ACROSS SKIN. “STIMULUS ARTIFACT” can distort/obliterate the smaller signal being recorded from nerve/muscle unless diverted to resistance pathway to earth. E.g. Ulnar nerve stimulated @ elbow + EMG from finger muscles recorded, ground electrode on wrist would catch stimulus artifact before reaches fingers
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20
Q

What is a patient cable in ECG?

A

Bundle of wires that the electrodes are attached to

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21
Q

What is fxn of patient cable

A

Wires transmit electric signal from electrode to ECG

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22
Q

List the five features/controls that most ECGs have in common

A
  1. Calibration button
  2. Sensitivity selection
  3. Lead selector button
  4. Chart speed selector switch
  5. Auxiliary output terminal
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23
Q

Fxn of calibration button?

A
  • Depressing button generates 1 mV calibration signal
  • Tracing of calibration signal needs to be recorded at beginning and end of each series of ECG recordings
  • Essential for calculation of AMPLITUDES e.g. QRS amplitude
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24
Q

Fxn of sensitivity selection aka gain selector

A
  • Allows magnify or suppress amplitude of recording
  • Sensitivity should be set that tracing occupies as much of paper as possible
  • Settings of 0.5, 1.0, 2.0 cm/mV; 1.0 cm/mV is STANDARD
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25
Q

What is a lead selector button

A

Lead is specific configuration, or combo, of electrodes e.g. 12-lead ECG obtained w/only 10 electrodes

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26
Q

What is chart speed selector switch fxn

A
  • Machines allow choice btwn 25-50 mmxs^-1
  • Chart speed is recorded on ECG tracing so that intervals e.g. HR, PR interval, QRS duration, QT interval) can be calculated.
  • Usually choose 25 mmxs^-1 cause sufficient precision on horizontal (time) scale. Also creates compact recording + conserve chart paper
  • Faster chart speed = able to look more carefully at changes in interval durations
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27
Q

What is the auxiliary output terminal

A

This socket can receive a cable, which will carry ECG signal to another output device like oscilloscope or computer

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28
Q

What happens when current flows towards the positive electrode?

A

Needle on ECG deflect upwards

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29
Q

What happens when current flows away from the positive electrode?

A

Needle on ECG deflect downwards

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30
Q

What is needed to eliminate 60 Hz interference

A
  1. Good skin prep
  2. Presence of differential amplifier
  3. Reference electrode
  4. Adequate grounding
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31
Q

What is the ideal configuration for patient, ECG etc

A

Recording device btwn patient and power source

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32
Q

How is technical problem: skeletal muscle tremor caused? How does it look on ECG? How to prevent

A

Talking laughing shivering or skeletal muscle contractions

  • irregular in height n frequency
  • tell them to hold still
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33
Q

How is technical problem: motion artifact

A
  • slipping of electrodes over surface of skin

- sudden large upward/downward deflection on ECG

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34
Q

How is technical problem: wandering baseline

A
  • whole tracing moves up or down
  • excessively deep respiration, by electrode paste drying up, electrode pulling away from skin, excessive tension on patient cable
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35
Q

What does PAR Q stand for

A

Physical Activity Readiness Questionnaire

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36
Q

What is PAR Q recommended as

A

Min standard of entry for low-mod intensity exercise programs

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37
Q

What was PAR Q designed for

A

Identify small # of adults for whom PA is inappropriate for

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38
Q

What result on PAR Q would mean the individual should consult his or her physician?

A
  • 7 yes/no Q’s (7 of 19 that were shown to be the best predictors of those individuals at risk to exercise)
  • A yes response to one or more means individual should consult physician
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39
Q

Of the 7 item q in PAR Q, how many should consult physican on average. Are all these truths

A
  • 26% would need to consult physician
  • 1/3 of these false pos aka no basis for advising against
  • 5% false neg aka 5 of 100 cautioned against exercise would answer “no” to all 7 q’s
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40
Q

Ischemic heart disease fuxn of?

A

Genetics, aging, lifestyle factors

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41
Q

3 reasons for exercise stress testing?

A
  1. To diagnose abnormal response to exercise denoting CVD
  2. To assess PA of patients w/known CVD
  3. TO assess PA of individuals without known CVD
42
Q

How are exercise stress tests designed

A
  1. Single stage where work rate is constant

2. Multistage bike or treadmill w/several work periods, each performed at higher work rate

43
Q

Purpose of small increments in WR

A

Determine threshold for myocardial ischemia

44
Q

What is ramp protocol

A

Inc at constant continuous rate

45
Q

Ideal total test time

A

8-12 mins

46
Q

How do tests end

A
  1. Reach certain objective criteria e.g. onset of angina

2. Fatigue (reached individuals max physical working capacity)

47
Q

What should precede stress test

A

ECG and BP measurement (baseline to which exercise ECG can b compared to)

48
Q

What is stress test limited in

A

Inability to show extent n specific location of disease

49
Q

Criterion measure of CAD?

A

Abnormal coronary angiogram

50
Q

Angiogram % of false negs

A

30

51
Q

What is sensitivity

A

% of patients w/disease who have an abnormal test

- % of patients w/disease correctly identified on exercise testing

52
Q

What is specificity

A

% of patients w/out disease who have normal test

- % of patients w/out disease correctly identified on exercise testing

53
Q

What is fxnal capacity

A

Highest WR completed in exercise test before exhaustion

54
Q

What is fxnal capacity depended on

A

Gender and age

55
Q

What is angina

A

Pain or discomfort in upper chest region caused by hypoxia caused by ischemia

56
Q

What med can be prescribed to angina patients

A

Nitroglycerine tablets which dilate coronary arteries

57
Q

How is insufficient oxygen supply to myocardium detected or coronary insufficiency

A

ST segment depression of one mm or more below ECG isoelectric line

58
Q

Magnitude of myocardial ischemia proportional to ___

A

amt of ST depression, number of ECG leads involved, duration of ST segment depression in recovery

59
Q

What is PVC? Caused by? Looks like?

A

Premature ventricular contractions, when ventricles demonstrate disorganized electrical activity

  • Portions of ventricle become spontaneously depolarized
  • Abnormal, high, long duration QRS
60
Q

Should exercise be stopped if see PVC

A

No, only if more than 30% beats are PVC, if they appear at diff phases of cycle, or R portion of PVC superimposed on normal T wave

61
Q

How does ventricular fibrillation look like

A

Irregular appearance

  • ventricles don’t contract in coordinated manner
  • CO falls
62
Q

How does abnormal HR response during exercise n recovery look compared 2 normal

A

Normal: progressive inc in HR w/WR. Rapid return of HR 10-20 beats/min above pre-exercise lvls w/in min or two of cessation of exercise
Abnormal: rapid, large inc in HR early in exercise or continued elevation of HR after exercise terminated

63
Q

Fxn of beta blockers

A

Suppress HR response to exercise

64
Q

Fxn of beta blockers

A

Suppress HR response to exercise

65
Q

What is normal BP response to graded dynamic exercise is a progressive inc in systolic BP from __ to ___

A

120 to 190 mm Hg

66
Q

How much does diastolic BP change w/exercise

A

Less than 10mm

67
Q

When should exercise be discontinued

A

Systolic BP of >250 of diastolic BP >115

68
Q

Max exercise systolic BP of ____ suggests poor prognosis

A

<140

69
Q

What are some signs n symptoms of exercise stress test indicating CVD

A
  • Clammy skin
  • Persistent fatigue
  • Blueness of lips or nails
70
Q

How to terminate exercse

A

Thats enough for today

71
Q

How to calculate heart rate thru arthmitic:

5 cardiac cycles span 80 mm, chart speed is 25 mm/s

A

5 beats/100mm x 25mm/s x 60s/min = 94beats/min

72
Q

Method 2 of HR

A

HR (b/min) = 1500/R to R distance

73
Q

Method 3 of HR

A
  • Count .5 squares btwn two adjacent QRS

- 1 square is 300 beats/min, 2 is 150 beats/min

74
Q

What is the mean electrical axis

A

Avg of all instantaneous vectors that are generated as ventricles depolarize

75
Q

What is a normal mean electrical axis

A

-30 to +105 degrees

76
Q

When is there a left axis deviation

A

Les than -30

77
Q

When is there a right axis deviation

A

More than +105

78
Q

How does the heart hang during inspiration vs. expiration

A

Inspiration: more vertically, inc mean electrical axis e.g. 59 to 90
Expiration: more horizontal, dec mean electrical axis

79
Q

How can pathology alter mean electrical axis of heart

A
  • Hypertrophy of one side of ventricle displaces vector to that side cause more electrical activity there e.g. left ventricular hypertrophy dec MEA
80
Q

What is exercise 1 (20 mins)

A

Deliberately Producing Technical Problems in an ECG

81
Q

What is aim of exercise 1

A

Understand causes of 4 technical problems encountered in ECG

82
Q

What are the 4 technical problems

A
  1. 60 Hz interference
  2. Skeletal muscle tremor
  3. Motion artifact
  4. Wandering baseline
83
Q

What are the steps in 60 Hz interference (4)

A
  1. Prep skin (ethanol wipe and shaving if necessary) + use electrode paste or disposable electrodes. Put limb electrodes on subject n record Lead I trace
  2. Remove lead wire from right leg electrode and record lead I trace
  3. Replace lead wire from RL electrode n put power cord near subject or have subject grasp power cord. Record Lead I trace.
  4. Disable filter fxn on ECG machine and repeat #3
84
Q

What are the steps in Skeletal Muscle Tremor (1)

A

Perform one of the following: Valsalva maneuvar, talking, isometric contraction of forearms. RECORD LEAD I TRACE

85
Q

What are the steps in Motion Artifact (1)

A

Gently tug on lead wires in patient cable. Record Lead I trace

86
Q

What are the steps in Wandering baseline (1)

A

Perform deep breathing. Record Lead I trace.

87
Q

What is exercise 2 (45 mins)

A

Resting 12-lead ECG from one individual

88
Q

Aim of resting 12 lead ECG from one individual?

A

Obtain 12 lead ECG from one subject at rest

89
Q

Procedure for exercise 2

A
  1. Locate positions of 6 chest electrodes
  2. Mark each positions w/inedible marking pen
  3. Prep skin at each site
  4. Prep skin at anterior aspect of both wrists n at meial aspects at both ankles just superior to medial malleolus
  5. Position subject supine
  6. Apply pre galled dispoable electrodes to wrists n ankles
  7. apply pre galled and disposable electrodes to chest sites
  8. Attach each wire to appropriate electrfoe.
  9. Record subjects name, gender, n age on beginning of tracing
  10. Write chart speed at beginning
  11. Record calibration signal
  12. Record short strip (20-25cm) from lead I and label “I” on this tracing
  13. Record short strip from each of the other 11 leads. Label each strip w/lead from which it was recorded
  14. Mount a short (3-4 QRS complexes) piece of training
90
Q

What is exercise 3

A

Effect of Respiration on MEA of heart

91
Q

What is aim of exercise 3

A

Observe effects of respiration on MEA of heart

92
Q

Procedure for exercise 3

A
  1. Same subject. Wrist n ankle electrodes needed
  2. Sitting up on table NOT SUPINE
  3. Breathe normally
  4. Record short (3-4 QRS complexes) strip of each of Leads I and III
  5. Inspire 3 quarters of max inspiration, and hold inspiration
  6. Record another short strip 3-4 QRS complexes
  7. Perform 3/4 max expiration and hold. Record short strips from Lead I and III
  8. Calculate MEA of heart for normal breahting, inspiration, expritation
  9. Power off ECG, remove wires from electrodes, remove electrodes from subject, clean electrode paste off subject w/water n kleenex
93
Q

What is exercise 4

A

Changes in ECG during dynamic exercise

94
Q

Aim?

A

Observe changes in ECH during dynamic exercise

95
Q

Time for ex 4

A

20 mins

96
Q

Procedure for exercise 4 changes in ECG during dynamic exercise

A
  1. Prep subject
  2. Place electrodes:
    Typically LA (pos) wrist, RA (neg) wrist, RL (reference) ankle. But movement causes wandering baseline and movement artifacts. So, LA is positioned at V6, RA is at right side of chest (bilaterally symmetrical to V6), reference at FLAT PORTION of RIGHT SCAPULA or 7th cervical vertebra
  3. Subject seated on bicycle ergometer
  4. Record calibration signal
  5. Record short (20-25cm) strip from Lead I at chart speed of 50 mm. Label as PRE EXERCISE
  6. Moderately heavy work rate (80% max HR). Tension is 1.5 kp and frequency is 60 rpm. Bike for 4 mins
  7. Record ECG for Lead 1 at 3:40
  8. After 1 min of recovery, record final ECG and label Recovery.
97
Q

Placement for V1?

A

Right border of sternum in 4th intercoastal space

98
Q

Placement for V2?

A

Left border of sternum in 4th intercoastal space

99
Q

Placement for V3?

A

Halfway btwn sites for V2 and V4

100
Q

Placement for V4?

A

along a vertical line drawn downward from middle of clavicle at lvl of 5th intercostal space

101
Q

Placement for V5?

A

anterior axillary line at same lvl of V4 (5th intercostal space)

102
Q

Placement for V6?

A

mid axillary line at same lvl of V4 (5th intercostal space)

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