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CVS > Session 7: ECG 2 > Flashcards

Session 7: ECG 2 Flashcards

1
Q

Which is the rhythm strip?

A

Lead II It is used because it is usually best for looking at p waves.

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2
Q

What is a heart block?

A

An atrioventricular conduction block where there is a delay or failure of conduction of impulses from atrium to ventricles via AV node and bundle of His.

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3
Q

What types of heart block exist?

A

First degree heart block Second degree heart block (mobitz type 1 and mobitz type 2) Third degree heart block also called complete heart block.

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4
Q

Causes of heart block.

A

Acute myocardial infarction (usually of right coronary artery) Degenerative changes

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5
Q

What does 1st degree heart block look like?

A

Prolonged PR interval that is longer than 0.2 seconds (5 small boxes)

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6
Q

What does 2nd degree heart block mobitz type 1 look like?

A

Successively longer PR intervals until on QRS complex is dropped/skipped. After a QRS complex is dropped the cycle starts all over again.

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7
Q

What does 2nd degree heart block mobitz type 2 look like?

A

PR intervals do not lengthen but instead the QRS complexes are dropped in a random manner.

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8
Q

Complication of 2nd degree heart block mobitz type 2.

A

High risk of progression to complete heart block (3rd degree).

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9
Q

Post-exposure prophylaxis of 2nd degree heart block mobitz type 2.

A

Pacemaker to reduce risk of complete heart block.

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10
Q

What is complete heart block?

A

Complete failure of atrioventricular conduction so the atria and ventricles are depolarising independently.

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11
Q

How do the ventricles contract if there is no connection between the atria and ventricles in complete heart block?

A

The ventricular pacemaker takes of also called ventricular escape rhythm.

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12
Q

What will complete heart block look like on an ECG?

A

Usually wide QRS complex. There is no connection between P waves and QRS complex aka P wave is not followed by a QRS complex. The ventricular rate is usually very slow at 30-40 bpm and often too slow to maintain an adequate blood pressure. P-P intervals are usually constant and around ~90 bpm.

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13
Q

Treatment of complete heart block.

A

Urgent pacemaker insertion is usually required.

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14
Q

What is a bundle branch block?

A

A delayed conduction in the branches of the bundle of His. Can be right bundle or left bundle branch.

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15
Q

How would a bundle branch block look on an ECG?

A

P wave and PR interval will be normal. A wide QRS complex over 3 small boxes since ventricular depolarisation takes longer.

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16
Q

If there is a left bundle branch block. Give an example of a lead which will detect this.

A

V6 and probably V5 as well.

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17
Q

Where can abnormal rhythms arise from?

A

Sinus node Atrium AV node Ventricle

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18
Q

What do supraventricular rhythms mean?

A

Rhythms which arise from above the ventricle. Sinus node Atrium AV node

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19
Q

Give an example of a abnormal supraventricular rhythm.

A

Atrial fibrillation.

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20
Q

Explain atrial fibrillation.

A

Rhythm which arise from multiple atrial foci resulting in rapid and chaotic impulses. Impulses will reach the AV node at rapid irregular rate where all of the impulses are not conducted because of the AV node refractory period.

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21
Q

What does atrial fibrillation look like on an ECG?

A

No p-waves with just wavy baseline. Narrow (normal) QRS complexes but irregular R-R intervals.

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22
Q

Haemodynamic effects of atrial fibrillation.

A

Atrial contraction is lost so they just quiver Ventricles contract normally but at an irregular rate Heart rate and pulse will be irregular.

23
Q

What are ventricular ectopic beats?

A

Impulse does not spread via the fast His-Purkinje system. This is because there is an ectopic focus (origin of the impulse is from somewhere else within the walls of the ventricles. This causes much slower depolarisations of ventricular muscle and a wide QRS complex which is different in shape to the usual QRS.

24
Q

Definition of ventricular tachycardia.

A

Run of 3 or more consecutive ventricular ectopics on an ECG. Persistent ventricular tachycardia is a dangerous rhythm.

25
Q

Complication of ventricular tachycardia.

A

Ventricular fibrillation

26
Q

Explain ventricular fibrillation.

A

Abnormal, chaotic, fast ventricular depolarisation. There are impulses from numerous ectopic sites in ventricular muscle. This is similar to ventricular tachycardia but more ectopic beats. There is no co-ordinated contraction and the ventricles ‘quiver’.

27
Q

Complication of ventricular fibrillation.

A

No cardiac output and cardiac arrest.

28
Q

What’s wrong?

A

2nd degree heartblock Mobitz type 2

Irregular rhythm

60 bpm

P waves present

29
Q

What’s wrong?

A

Irregular rhythm

80 bpm

No p waves

Atrial fibrillation

30
Q

What’s wrong?

A

Ectopic ventricular beat

31
Q

What’s wrong?

Atrial heart rate.

Ventricular heart rate.

A

Complete heart block.

Ventricular heart rate at around 20bpm

Atrial heart rate at around 60 bpm

32
Q

Classification of arrhythmias.

A

Bradycardia or Tachycardia?

If bradycardia = heartblock or simple brady cardia

If tachycardia -> narrow complex or broad complex? (QRS)

If narrow complex = Afib or flutter, supraventricular tachycardia, sinus tachycardia

If broad complex = ventricular tachycardia, ventricular fibrillation

33
Q

Which leads look at right coronary artery?

A

Lead II, III and aVF

34
Q

Which leads look at left anterior descending artery?

A

Anteroseptal leads V1-V4.

35
Q

Which leads look at circumflex artery?

A

Lead I, aVL, V5 and V6.

36
Q

In what relation can leads look at arteries?

A

If there is an obstruction of an artery that area of the heart will not depolarise correctly.

37
Q

How do you distinguish between ischaemia and myocardial infarction?

A

In ischaemia without muscle necrosis Troponin-I/Troponin-T assay will be negative.

However in MI where there is muscle necrosis Troponin-I/Troponin-T will be positive.

38
Q

What is a STEMI?

What is it due to?

A

A ST segment elevation myocardial infarction.

Due to complete occlusion of coronary artery by thrombus.

This means that the full thickness of myocardium is involved.

Sub epicardial injury causing ST segment elevation in leads facing affected area is the earliest sign.

39
Q

Theory of why ST elevation happens in STEMI.

A

Abnormal current coming towards injured epicardium during repolarisation.

40
Q

What does this show?

Which artery is affected?

In which leads can you find abnormality?

A

STEMI shown in lead II, Lead III and aVF.

This shows STEMI from obstruction of right coronary artery.

41
Q

Evolving changes of STEMI.

A

Acute change will be ST elevation. The injury is shows as ST elevation.

After a few hours the Q waves might start to deepen this is due to necrosis.

The R wave will go down.

After few days T wave will invert and Q wave will get even deeper.

Days later ST normalises again and T wave is still inverted.

The final outcome is ST and T normal again but Q wave is still deepened.

42
Q

What does this show?

Which leads should you look at?

Which artery is involved?

A

STEMI shown in V1-V4.

Shows a obstruction of left anterior descending artery.

43
Q

Why does necrosis cause Q waves?

A

In MI dead muscle tissue produces no AP and ECG looks through infarcted area to pick up electrical forces from opposite side of heart.

44
Q

Features of pathological Q waves.

A

Larger than 1 small box wide >0.04s (>40ms)

Larger than 2 small boxes deep

Depth more than 1/4 of the height of subsequent R wave

45
Q

What does this show?

A

An old STEMI with pathological Q waves in lead V1 to V4.

Means there is damage in the anterior area of the heart.

46
Q

What is a non-STEMI also called NSTEMI?

A

An MI due to sub endocardial injury.

47
Q

How will the ECG manifest itself in an NSTEMI?

A

ST sement depression and T wave inversion

48
Q

NSTEMI and unstable angina look very similar in ECG changes with both T wave inversion and ST depression.

How can you differentiate between the two?

A

Unstable angina will not have elevated Troponin-I/Troponin-T.

Blood test done.

49
Q

How will ECG changes differ after an NSTEMI/Unstable angina.

A

In actue there can be ST depression or T-wave inversion or both.

Weeks later ST and T will be normal but there will be no Q waves.

50
Q

What does stable angina look like at rest?

A

The ECG is normal at rest.

51
Q

What will stable angina look like when exercising?

A

ST depression but will reverse again when going back to rest.

52
Q

ECG changes in hyperkalaemia.

A

Resting membrane potential is less negative which will inactivate some voltage gated Na+ channels meaning the heart will become less excitable.

This leads to tall peaked T wave, flattened p wave, prolonged PR interval, widened QRS complex, ST segment merging with T wave.

The symptoms will show in this succession as the hyperkalaemia gets worse.

53
Q

Changes in ECG in hypokalaemia.

A

Low T wave

High U wave

Low ST segment

CVS (18 decks)

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