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CAM201 Physiology > The Normal ECG > Flashcards

The Normal ECG Flashcards

1
Q

Why is atrial repolarisation not seen on ECG?

A

Because it happens at the same time as ventricle depolarisation, which is stronger

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2
Q

What does a P wave represent?

A

atrial depolarisation

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3
Q

What does a T wave represent?

A

Ventricular depolarisation

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4
Q

What does a U wave represent?

A

Unsure. Potentially the repolarisation of papillary and accessory muscles

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5
Q

What is a dipole?

A

A pair of equal and oppositely charged poles separated by a distance.

Reference must be negative and sensor must be positive

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6
Q

How do cells create a dipole?

A

If one is depolarised and one adjacent cell is resting, there is a dipole created due to the difference in electrical currents

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7
Q

What does a negative reading represent?

A

When the first cell repolarises, a reversal of the dipole occurs, the current wants to go towards the reference

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8
Q

What does the absence of a dipole represent?

A

When both cells are repolarised

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9
Q

What does a dipole require to be set up?

A

A conductive medium e.g. water.

Orientation and position of electrodes matters

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10
Q

How is the dipole measured in the heart when there are many different dipoles in different directions?

A

It is measured by the net dipole i.e. the sum of all vectors (diretion and magnitude). Generally DOWN when the myoseptum is depolarising

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11
Q

What is a lead?

A

A pair of electrodes that have a specific orientation, allowing you to measure from a reference point to a sensor

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12
Q

What does depolarisation heading in the same direction as a lead produce?

A

POSITIVE deflection

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13
Q

What does depolarisation heading in the opposite direction to a lead produce?

A

NEGATIVE deflection

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14
Q

What does depolarisation heading perpendicular to the direction of a lead produce?

A

ZERO deflection

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15
Q

What does repolarisatin heading in the same direction as a lead produce?

A

NEGATIVE deflection

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16
Q

What does repolarisation heading in the opposite direction to a lead produce?

A

POSTIVIE deflection

17
Q

What does repolarisation heading perpendicular to the orientation of a lead produce?

A

ZERO deflection

18
Q

What happens if a signal is not travelling horizontally or vertically?

A

The voltage recorded by a lead is simply the component of the depolarisation vector that is running/leaning in that direction

19
Q

What happens if two leads are measuring at the same time?

A

The net depolarisation vector can be determined. Each deflection will equate to the strength of the signal in that direction.

20
Q

What does the PR segment represent?

A

Delay at the AV node

21
Q

What does the QRS complex represent?

A

ventricular depolarisation

22
Q

what does an isoelectric line represent?

A

no electrical activity

23
Q

What are some uses of the ECG?

A
  • measure HR
  • determine which part of the heart is acting as the pacemaker
  • assess for enlargement
  • assess for blockages
  • look for signs and location of ischaemic injury
  • look for signs of electrolyte abnormalities
24
Q

What does the Wigger’s diagram show us?

A

Electrical activity, left ventricular volume and pressure

25
Q

What is Einthoven’s triangle?

A

The basic 3 lead ECG

Lead I: RA-LA
Lead II: RA-LL
Lead III: LA - LL

26
Q

What are augmented limb leads?

A

Leads that are produced without extra cables. They use two existing points as a negative

27
Q

What are the three augmented limb leads?

A

aVF: femoral: LL - (RA+LA)

aVR: Right arm: RA - (LA+LL)

aVL: Left arm: LA- (RA+LL)

28
Q

What is the axial reference system? What does it measure?

A

Axial reference system is created by superimposing all 6 limb leads over the heart

Can give an indication of the location of the heart in the thoracic cavity and hence any hypertrophy

29
Q

What is a normal cardiac axis?

A

-30 to +90

30
Q

What is Right axis deviation? What does it indicate?

A

90 - 180

indicates RV hypertrophy

31
Q

What is left axis deviation? What does it indicate?

A

-90 to -30

LV hypertophy

32
Q

What is extreme axis deviation?

A

No man’s land

180 to -90

33
Q

What are chest leads and what do they do?

A

6 leads that allow us to look at the heart in 3D and show us the exact location of where the ischaemia or issue is. all measure the current coming towards them

CAM201 Physiology (4 decks)

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