ECGs Flashcards

1
Q

ECG lead I measures conduction in what aspect of the heart?

A

Left lateral

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2
Q

ECG lead II measures conduction in what aspect of the heart?

A

Left lateral

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3
Q

ECG lead III measures conduction in what aspect of the heart?

A

Inferior

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4
Q

aVR lead measures conduction in what aspect of the heart?

A

Right atrium

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5
Q

aVL lead measures conduction in what aspect of the heart?

A

Left lateral

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6
Q

aVF lead measures conduction in what aspect of the heart?

A

Inferior

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7
Q

V1 lead measures conduction in what aspect of the heart?

A

Right ventricle

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8
Q

V2 lead measures conduction in what aspect of the heart?

A

Right ventricle

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9
Q

V3 lead measures conduction in what aspect of the heart?

A

Interventricular septum

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10
Q

V4 lead measures conduction in what aspect of the heart?

A

Interventricular septum

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11
Q

V5 lead measures conduction in what aspect of the heart?

A

Left ventricle

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12
Q

V6 lead measures conduction in what aspect of the heart?

A

Left ventricle

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13
Q

Which leads are said to be bipolar?

A

Red, yellow and green limb leads

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14
Q

What is first degree heart block (also called AV block)?

A

Slowing of conduction through the AV node meaning ventricles take longer to depolarise

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15
Q

How is first degree/AV block recognised on an ECG?

A

Prelonged P-R interval of more than 0.2 seconds

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16
Q

What is third degree heart block?

A

Complete blockage of conduction anywhere downstream of the AV node

17
Q

How is third degree/complete heart block recognised on an ECG?

A

P wave : QRS complex appear completely unrelated with distorted firing ratio (eg. 8 p waves for each QRS complex)

Bradycardia

18
Q

Third degree heart block is complete blockage of conduction anywhere downstream of the AV node. Based on this, why is there still ventricular firing seen on an ECG trace?

A

Ventricles form a ventricular subsidiary pacemaker. This is able to initiate a separate heart beat at around 40bpm

19
Q

What is atrial fibrillation?

A

Rapid and irregular beating of the atria initiated by electrical activity independent of the SA node

20
Q

What are the consequences of prelonged and sustained courses of AF?

A

Irreversible electrical remodelling

21
Q

AF is initiated by rapid electrical activity independent of the SA node. From where does this independent activity of AF often come from?

A

Arrythmogenic foci located in muscular sleeves of pulmonary veins

22
Q

How is AF recognised on an ECG?

A

Irregularly irregular pulse
Absence of a clear P wave
PR interval immeasurable

23
Q

How is ST elevation recognised on an ECG?

A

ST segment elevated greater than 1mm in 2 or more limb leads OR 2mm or more in 2 or more chest leads

24
Q

What limb lead measures conduction in the horizontal axis?

A

Lead I

25
Q

What limb lead measures conduction in the vertical axis?

A

aVF

26
Q

What are the precordial ECG leads? What do they measure?

A

V1 to 6

Electrical activity on a transverse plane

27
Q

What are the augmented leads?

A

aVR
aVL
aVF

28
Q

What are the bipolar limb leads?

A

Lead I
Lead II
Lead III

29
Q

What are the two factors that determine ECG deflection?

A
Flow direction (towards/away from the electrode)
Depolarisation/repolarisation
30
Q

Depolarisation travelling towards an electrode would produce a ……… deflection?

A

Positive

31
Q

Repolarisation travelling towards an electrode would produce a ……… deflection?

A

Negative

32
Q

Depolarisation travelling away from an electrode would produce a ……… deflection?

A

Positive

33
Q

Repolarisation travelling away from an electrode would produce a ……… deflection?

A

Negative

34
Q

A current travelling neither towards nor away from an electrode would produce a …….. deflection?

A

No deflection