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103 Theme 3 > Lecture 6: Intro to the ECG > Flashcards

Lecture 6: Intro to the ECG Flashcards

1
Q

what is a syncytium

A

one large cell having many nuclei that are not separated by cell membrane

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2
Q

what is a functional syncytium

A
  • many cells functioning as one

- large groups of cells make electrical changes simultaneously

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3
Q

in which order are parts of the ventricular wall depolarised

A

1) septum
2) apex
3) atrioventricular groove

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4
Q

what is the ECG good for measuring

A
  • heart rate, with Holter moniter

- especially when atrial rate is not equal to ventricular rate

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5
Q

where are the electrodes in lead II

A

pos: left leg
neg: right arm
ground: right leg (but could be almost anywhere)

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6
Q

how many leads are in a standard ECG

A
  • 3 bipolar leads: leads I,II and III let us see in frontal plane
  • 3 augmented leads in frontalplane
  • 6 precordial in transverse plane
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7
Q

what does a wide or misshapen QRS wave suggest

A
  • ectopic pacemaker

- bundle branch block

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8
Q

what does a large Q wave suggest

A

dead tissue, eg from an old myocardial infarction

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9
Q

what is sinus rhythm

A

when the heart rhythm is generated from the SAN

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10
Q

what are indicators that the heart is in sinus rhythm

A
  • each P wave matched with QRS complex

- PR interval always normal, 4-5 little boxes

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11
Q

what is sinus tachycardia

A

tachycardia driven by SAN beating too quickly

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12
Q

what are the sizes of the boxes in an ECG

A

small box 40 ms
big box is 200 ms
5 big boxes is 1 sec

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13
Q

what is the height of each little box in an ECG

A

0.1 mV

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14
Q

where is the PR interval

A

start of P wave to start of QRS complex

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15
Q

where is the PR segment

A

end of P wave to start of QRS complex

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16
Q

where is the ST segment

A

end of QRS complex to start of T wave

17
Q

where is the QT interval

A

start of QRS complex to end of T wave

18
Q

PR interval duration

A

3 - 5 boxes

120 - 200 ms

19
Q

QRS complex duration

A

2 - 3 boxes

80 - 120 ms

20
Q

QT interval duration

A

9 - 11.5 boxes

360 - 460 ms

21
Q

how do you calculate ventricular rate from an ECG

A

count between R waves

22
Q

how do you calculate atrial rate from an ECG

A

count between P waves

23
Q

how to calculate heart rate from ECG

A

300 divided by number of big boxes

24
Q

what is the parasympathetic pathway of the heart

A

vagus nerve stimulates muscarinic receptors

25
Q

what does atropine do

A
  • muscarinic antagonist

- causes parasympathetic withdrawal

26
Q

what is the sympathetic pathway to the heart

A
  • stellate nerves
  • beta agonists increase rate
  • beta blockers decrease rate
27
Q

what is a heart block

A
  • type of dysrhythmia

- any blocking of impulse conduction of the heart

28
Q

what are causes of AV heart blocks

A
  • ischaemia of AV node or bundle
  • compression of AV bundle by scar or calcified tissue
  • inflammation of AV node or bundle
29
Q

symptoms of AV heart blocks

A
  • can be asymptomatic
  • palpitations
  • hypotension-like:
  • dizziness
  • malaise
  • syncope
  • if serious, risk of sudden cardiac death
30
Q

what is 1st degree heart block

A
  • PR interval > 5 little boxes

- caused by delayed AV node transmission

31
Q

what is Mobitz Type I

A
  • type of second degree heart block
  • aka Wenckebach
  • PR interval gets longer until QRS wave fails to follow P wave
  • caused by AV node damage
32
Q

what is Mobitz Type II

A
  • type of second degree heart block
  • aka Hay
  • PR interval stays the same, some not followed by QRS wave
  • caused by problem in bundle of his
33
Q

what is third degree heart block

A
  • atrial signals fail to reach ventricles
  • PR intervals vary radically, sometimes >12 boxes
  • very dangerous
34
Q

what are premature beats

A

individual early beats triggered by irritable tissue

35
Q

what are escape beats

A

individual late beats triggered by lack of stimulation from atria

36
Q

what are premature ventricular contractions

A
  • unusually wide ventricular activity

- no S wave and negative dip where T wave should be

37
Q

what is atrial fibrillation

A
  • very common in elderly
  • disorganised electrical activity in atria
  • no P wave, but flat or wiggly line
  • ventricular rate is fast and irregular
  • AVN only lets some signals from atria to ventricles
38
Q

what is respiratory sinus arrhythmia

A
  • sign of healthy heart, seen in children and athletes

- heart beat slightly faster during inspiration, slower during expiration

103 Theme 3 (17 decks)

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