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CVS (Semester 2) > ECG > Flashcards

ECG Flashcards

1
Q

What in the heart does an ECG look at?

A

It looks at the electrical activity.

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2
Q

What about the cell are we recording in an ECG?

A

This is Extracellular recording and so we are measuring changes in membrane potential.

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3
Q

How is conduction spread across the atria?

A

The SA node in the right atria initiates depolarisation. This spreads through the backmann’s branch to the left atria.

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4
Q

What happens at the AV node?

A

There is a slight pause in conduction, this because it takes time for the signal to conduct through the node and gives time for the ventricles to fill following atrial systole.

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5
Q

Where does conduction spread after the bundle of his?

A

It spreads into the left and right bundle branches. It then spreads into the purkinje fibres.

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6
Q

In what direction does repolarisation of the cardiac muscle occur?

A

From the epicardium surface to the endocardial surface.

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7
Q

In an ECG, what two planes are we looking at the heart from?

A

Horizontal and coronal.

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8
Q

What two things give a positive deflection from the baseline on an ECG lead?

A

Depolarisation towards the electrode and repolarisation away from the electrode.

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9
Q

What affects the height of a deflection in an ECG?

A

This depends on whether the signal is moving directly towards to electrode or is moving past it.

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10
Q

What wave in an ECG shows ventricular repolarisation?

A

T

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11
Q

What does the R wave in the ECG show?

A

Ventricular depolarisation

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12
Q

What does the P wave in an ECG show?

A

Atrial depolarisation

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13
Q

Which wave signifies the end of ventricular depolarisation?

A

S

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14
Q

What does a Q wave show?

A

This shows septal depolarisation, spreading to the ventricle.

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15
Q

How do we calculate heart rate from an ECG when the rhythm is regular?

A

We count the number of squares between the R-R complexes and then divide 300 by this number.

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16
Q

When heart beat is irregular, how can we calculate the heart rate?

A

Number of beats over 30 squares, multiplied by 10

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17
Q

What is the PR interval? How long should it be?

A

From the end of P to the beginning of R. 3-5 small boxes

18
Q

How wide should the QRS complex be?

A
19
Q

What does a broad QRS suggest?

A

That the rhythm origin is the ventricles.

20
Q

What is sinus rhythm?

A

This is normal rhythm of the heart. Every p is followed by a QRS and every QRS is preceded by a p.

21
Q

What is sinus bradycardia?

A

This is when the rate is below 60 bpm.

22
Q

How can we describe a pulse when it is >100bpm?

A

Tachycardic

23
Q

What is atrial fibrillation?

A

This is when multiple abnormal pacemakers in the atria discharge randomly. This leads to loss of normal atrial contraction.

24
Q

Explain why QRS complexes remain narrow in atrial fibrillation?

A

Conduction to the ventricles still occurs in the same way, through the AV node and then into the bundle of his.

25
Q

What changes will be seen in an ECG is atrial fibrillation?

A

No p waves will be seen, and there will be irregular irregular QRS complexes.

26
Q

What is 1st degree heart block?

A

This is where there is prolonged conduction at the AV node and so there are normal p waves but then a lengthened PR interval before a normal QRS complex.

27
Q

If progressive PR lengthening and then dropping of a QRS complex is seen in an ECG then what does this indicate?

A

2nd degree heart block, type 1.

28
Q

What ECG changes are seen in type 2 second degree heart block?

A

PR interval is normal, but then there will be a sudden drop of a QRS due to failure to conduct. This is likely to progress to full heart block and so requires a pacemaker.

29
Q

How will an ECG of third degree heart block look?

A

There is no conduction of p waves, but p waves will look normal. Pulse will be very slow. QRS complexes will be wide because they are of ventricular origin.

30
Q

Where can ectopic beats occur? Why are they rare?

A

These can occur in the atria or the ventricles. They are rare because they are usually suppressed by the higher rate of the SA node.

31
Q

Why are QRS complexes wide for ectopic beats of ventricular origin?

A

Conduction through the muscle is much slower than through the purkinje fibres, and so it takes longer, broader QRS.

32
Q

What is ventricular fibrillation?

A

There is chaotic depolarisation of the ventricular muscle, due to numerous ventricular ectopic beats. This leads to no coordinated muscle contraction and therefore no cardiac output or pulse.

33
Q

If there is ischaemic heart disease, when is an ECG likely to show changes?

A

On exercise, as the heart is under higher demand and so the occlusion of the artery has a larger impact.

34
Q

On an ECG of a patient with who has suffered Mi, what changes may be seen:

A

T wave inversion, ST elevation, pathological Q waves

35
Q

What is a pathological Q wave?

A

This is a Q wave which lasts longer than 0.04 secs and are present in full thickness MI.

36
Q

What is seen on an ECG is left axis deviation?

A

Leads 1 and 3 are in opposite directions, leaving each other.

37
Q

What causes left axis deviation?

A

Blocks in anterior part of left bundle branch, or left ventricular hypertrophy.

38
Q

What can be said about an ECG if there is a negative lead 1 and a positive lead 3 (they are coming together)?

A

There is right axis deviation which can be due to right heart hypertrophy.

39
Q

What changes are seen on an exercise ECG of a person with ischaemic heart disease?

A

ST depression of the leads facing the affected area.

40
Q

The combinations of limb leads used to create leads 1,2,3

A

1 - LA and RA, 2 - LL and RA, 3 - LA and LL

41
Q

What do the leads aVR, aVL and aVF look at?

A

These compare one limb lead to the average of the other two (RL is not used - only an earth). aVL = LA, aVR = RA, aVF = LL

CVS (Semester 2) (17 decks)

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