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MD3001 Cardiology > Physiology of the ECG > Flashcards

Physiology of the ECG Flashcards

1
Q

What is P wave?

A
  • atrial depolarisation

- electrical activation

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2
Q

What is the PR interval?

A
  • the time taken for the electrical impulse to spread from the atria to the ventricles by the AV node and bundle of His
  • between 3-4 boxes
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3
Q

What is the QRS interval?

A

the impulse spreading through the ventricles in ventricular contraction

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4
Q

What is the ST interval?

A
  • the ventricles completely activated

- usually isoelectric

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5
Q

What is T wave?

A

repolarisation of the ventricular muscle to relaxed state

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6
Q

What are the letters to help remember what to check in an ECG?

A

R R P W Q S T

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7
Q

R (1)

A

Rate

  • the closer the QRS complexes, the faster the beat
  • tachycardia if >100 bpm
  • bradycardia if <50 bpm
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8
Q

R (2)

A

Rhythm

  • regular/irregular
  • determined by if the number of squares between QRS complexes are the same or not
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9
Q

P

A

P wave

  • sinus rhythm?
  • there should be one P wave for every QRS complex
  • no p-wave means no activation - abnormal rhythm
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10
Q

W

A

Width

  • if QRS >3 boxes then spread of electrical activity is slow
  • abnormal conduction
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11
Q

Q

A
  • are there deep Q waves?

- deep downward deflection can be due to old MI

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12
Q

S

A

ST interval

  • should be level with baseline
  • if elevated: MI
  • if depressed: ischaemia
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13
Q

T

A

T waves

- if upside down in I, II and V4-6: ischaemia/hypertrophy

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14
Q

Dextrocardia

A

Heart points in the opposite way

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15
Q

What direction is electrical activity going in to create the most deflection on an ECG?

A

parallel

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16
Q

What is the role of the electrode on the RIGHT leg?

A

neutral lead

17
Q

What does an ECG measure?

A
  • electrical activity from SA node spreading through ventricles
  • not how well heart is pumping
18
Q

When would you take an ECG on patient?

A
  • chest pain
  • palpitations
  • dizziness
  • syncope episode
  • stroke/TIA
19
Q

Why can’t we see atrial repolarisation on an ECG?

A
  • too small

- hidden by QRS complex

20
Q

How to calculate HR from ECG?

A
  • 300 big boxes = 1 minute

- 300/number of big boxes between QRS

21
Q

What characterises first degree heart block on an ECG?

A
  • prolonged PR interval

- AV node delays too long

22
Q

What characterises secondary degree heart block on an ECG/

A
  • 2 P waves for every QRS complex

- not all P waves resulting in QRS complex

23
Q

What characterises AF on an ECG?

A
  • no P wave
  • irregular QRS complexes
  • arrythmia
24
Q

What characterises atrial flutter on an ECG?

A
  • 4 P waves for every QRS complex

- arrythmia

25
Q

What characterises junctional (nodal) tachycardia on an ECG?

A
  • normal QRS
  • no P waves
  • arrythmia
26
Q

What characterises ventricular tachycardia?

A
  • after 2 sinus beats rate increases
  • wide QRS complexes
  • can return back to sinus beat
27
Q

What can abnormal P waves be a sign of on an ECG?

A

P-mitrale (left atrial hypertrophy): bifid P waves for every QRS

P-pulmonale (right atrial hypertrophy): peaked P wave

28
Q

What can abnormal QRS complexes be a sign of on an ECG?

A

Wide:
- ventricular conduction defects (bundle branch block)

Low voltage:

  • hypothyroidism
  • CAOD
  • myocarditis
  • pericarditis/pericarditis effusion
29
Q

What characterises left and right ventricular hypertrophy?

A
  • left ventricular hypertrophy: sum of S wave in V1 and R wave in V5/6 >35mm
  • right ventricular hypertrophy:
  • dominant R wave V1, T wave inversion V1-4, deep S wave V6
30
Q

How long is QT interval normally?

A

roughly 1 big box

31
Q

A prolonged QT interval is a sign of what?

A
  • acute myocardial ischaemia
  • myocarditis
  • bradycardia
  • head injury
  • hypothermia
  • U and E imblanace
  • congenital
  • drugs
32
Q

What effect does digoxin have on ECG?

A
  • T wave inversion

- ST segment sloping depression

33
Q

Left axis deviation

A
  • negative QRS in II and III
  • LV hypertrophy
  • MI
34
Q

Right axis deviation

A
  • negative QRS in I
  • RV hypertrophy
  • PE
  • MI

MD3001 Cardiology (56 decks)

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