Electrocardiography Flashcards

1
Q

What does the SAN do?

A

Spontaneously active cells

Conducts current down atria & internodal pathways

P-wave of ECG

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2
Q

What happens at the AVN?

A

Current slows down -> atrial muscle contraction

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3
Q

What happens at the septum and his-Purkinje fibres?

A

Current travels through septum -> His-Purkinje system

Rapid conduction through left & right bundle -> Purkinje fibres -> ventricular contraction
= QRS complex of ECG

Cardiac muscle relaxes & membrane potential
recovers/repolarises
= T-wave of ECG

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4
Q

how many leads in a normal ECG and what 2 areas are their placement split into?

A

10 electrodes-> 12 lead recording

Limb leads (coronal view)
Chest leads (axial view)

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5
Q

Where are limb leads placed?

A
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6
Q

Where are Chest leads placed?

A

V1: 4th intercostal space (ICS), right margin of the
sternum

V2: 4th ICS along the left margin of the sternum

V4: 5th ICS, midclavicular line

V3: midway between V2 and V4

V5: 5th ICS, anterior axillary line

V6: 5th ICS, mid-axillary line

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7
Q

What causes right axial and left axial deviation?

A

Gravity

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8
Q

what angles are Right axial and left axial deviation?

A

LAD= 0 to -90

RAD= 90 to 180

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9
Q

What does the biggest QRS complex show?

A

The deviation of the heart

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10
Q

What does atrial fibrillation lead to in terms of the ECG?

A

loss of p wave

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11
Q

What does atrial flutter lead to in terms of the ECG?

A

saw tooth pattern

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12
Q

What is rhythm?

A

movement of current, between P and QRS

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13
Q

What are the types of heart blocks?

A

1st, 2nd, 3rd

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14
Q

What affects the P-R interval?

A

conduction from atria to ventricles
- e.g., heart blocks

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15
Q

What does a 1st degree heart block do?

A

delay in conduction

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16
Q

What does 2nd degree heart block do?

A

loss of conduction

17
Q

What is a 3rd degree heart block?

A

a medical emergency

18
Q

What can happen to an ST segment in an ECG?

A

elevation or depression

19
Q

How do you calculate rate from an ECG?

A

300/ number of large squares between 2 QRS complex
(like the rox of squares)

20
Q

How do you calculate PR interval from an ECG and what is a normal PR?

A

5 x small squares

normal PR is 120-200ms

21
Q

How do you calculate QRS duration from an ECG?

A

2.5 x small squares

22
Q

What does an elevated ST segment?

A

ST elevated myocardial infarction

23
Q

What does a saw tooth pattern suggest?

A

atrial flutter

24
Q

What does a long PR interval suggest?

A

480ms

25
Q

What does a slow and regular heart rate, and P wave is only occasionally associated with QRS (2:1)?

A

second degree heart block

26
Q

What does a slightly depressed ST segment, and right axis deviation (120-150 degrees) suggest?

A

Right axis deviation (right ventricular hypertrophy/ pulmonary artery hypertension)

27
Q

How do you know there’s a RAD?

A

If the QRS is predominantly negative in lead I and positive in lead aVF, then the axis is rightward (right axis deviation).

28
Q

How do you know there is a LAD?

A

If the QRS is upright in lead I and downward (negative) in lead aVF, then the axis is between 0 and -90 degrees, likely left axis deviation.