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Semester 2-CVS > Session 7-ECG Abnormalities > Flashcards

Session 7-ECG Abnormalities Flashcards

1
Q

Which rhythms are classified as supraventricular rhythms?

A

1) sinus node
2) atrial
3) AV node

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2
Q

Which system conducts supraventricular rhythms into and within the ventricles?

A

His-Purkinje system

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3
Q

True or false: supraventricular rhythms have a broad complex

A

FALSE - narrow complex, ventricular rhythms have broad complex

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4
Q

Where do ventricular rhythms arise from?

A

Focus/foci in ventricle

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5
Q

True or false: the conduction of ventricular rhythms is not via usual His-Purkinje systems

A

TRUE

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6
Q

Describe atrial fibrillation

A

Impulses have chaotic, random pathways in atria

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7
Q

What do atria do in atrial fibrillation rather than contract?

A

Quiver

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8
Q

True or false: ventricles depolarise and contract normally in atrial fibrillation

A

TRUE

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9
Q

Describe the characteristics of an atrial fibrillation ECG (2)

A

1) absent p waves - wavy baseline

2) narrow QRS complexes which are irregularly irregular

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10
Q

What is an AV conduction block or ‘heart block’?

A

Delay/failure of conduction of impulses from atria to ventricles via AV node and bundle of Hiss

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11
Q

What is the most common cause of an AV conduction block?

A

Acute myocardial infarction

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12
Q

What are the three types of heart block?

A

1) first degree heart block
2) second degree heart block (mobitz 1 and mobitz 2)
3) third degree heart block or complete heart block (CHB)

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13
Q

Describe the characteristics of first degree heart block

A

1) p wave normal
2) slow conduction in AV node and His bundle
3) PR interval prolonged > 5 small squares
4) QRS Norma

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14
Q

What is another name for Mobitz type 1 (2nd degree heart block)?

A

Wenkebach phenomenon

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15
Q

Describe the characteristics of Mobitz type 1, second degree heart block

A

progressive lengthening of PR interval until one P is not conducted (allowing time for AV node to recover)

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16
Q

Describe the characteristics of Mobitz type 2, second degree heart block

A

1) PR interval normal
2) sudden non-conduction of a beat (dropped QRS)
3) high risk of progression to complete heart block

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17
Q

Describe the characteristics of third degree heart block

A

1) normal atrial depolarisation but impulses not conducted to ventricle
2) ventricular pacemaker takes over (ventricular escape rhythm) and this rate is very slow (~30-40bpm)
3) usually wide QRS complexes
4) HR often too slow to maintain BP and perfusion

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18
Q

What is the relationship between P waves and QRS complexes in third degree heart block?

A

No relationship

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19
Q

What happens in ventricular ectopic beats?

A

1) Ectopic focus in ventricle muscle
2) Impulse not spread via fast His-Purkinje system therefore much slower depolarisation of ventricle and therefore wide QRS complex

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20
Q

What is ventricular tachycardia?

A

Run of 3 or more consecutive ventricular ectopics

21
Q

What does someone with ventricular tachycardia have a high risk of?

A

Ventricular fibrillation

22
Q

Describe the characteristics of ventricular fibrillation

A

1) abnormal, chaotic, fast ventricular depolarisation
2) impulses from numerous ectopic sites in ventricular muscle
3) no coordinated contraction so ventricles quiver
4) no cardiac output -> cardiac arrest

23
Q

What does a patient with ventricular fibrillation require?

A

Immediate defibrillation to restore rhythm

24
Q

What is the difference between atrial and ventricular fibrillation?

A
  • VF has no coordinated ventricular contraction but AF does
  • VF has no cardiac output but AF does
  • VF has no pulse or heart beat but AF has irregularly irregular heart beat and pulse
25
Q

Which ECG leads look at the lateral side of the heart?

A

Lead I
AVL
V5
V6

26
Q

Which ECG leads look at the inferior side of the heart?

A

Lead II
Lead III
AVF

27
Q

Which ECG leads look at the septal side of the heart?

A

V1

V2

28
Q

Which ECG leads look at the anterior side of the heart?

A

V3

V4

29
Q

Which part of the muscle is furthest away from surface and therefore most vulnerable to MI?

A

Sub endocardial muscle

30
Q

What do ECG leads facing the affected sub endocardial region show in ischaemia/MI?

A

1) ST segment depression

2) T wave inversion

31
Q

When can ischaemic ECG changes be seen?

A

During exercise

32
Q

What is NSTEMI?

A

Non-ST elevation myocardial infarction

33
Q

What is STEMI and what is it due to?

A

ST segment elevation myocardial infarction

Due to complete occlusion of lumen by thrombus

34
Q

Where does muscle injury extend from and to in a STEMI?

A

Full thickness from endocardium to epicardium

35
Q

What do ECG leads facing the area show in an epicardial injury?

A

ST segment elevation

36
Q

What will happen in a STEMI if perfusion is not re-established?

A

Muscle necrosis follows

37
Q

What dimensions are classed as pathological Q waves?

A

1) >1 small square wide
2) >2 small squares deep
3) depth more than 1/4 height of subsequent R wave

38
Q

Describe the resting membrane potential in hyperkalaemia and how this affects conduction

A

Less negative -> inactivate some voltage gates Na+ channels -> heart becomes less excitable as hyperkalaemia worsens -> conduction problems

39
Q

Describe the resting membrane potential in hypokalaemia

A

More negative

40
Q

What does extreme hyperkalaemia lead to?

A

Ventricular fibrillation

41
Q

Describe the ECG changes in hyperkalaemia

A

1) high T wave
2) prolonged PR interval
3) depressed ST segment

42
Q

Describe the ECG changes in hypokalaemia

A

1) low T wave
2) high U wave
3) low ST segment

43
Q

What is cardiac axis?

A

Average direction of spread of ventricular depolarisation

44
Q

What is the normal cardiac axis?

A

-30 to +90 degrees (downward and to the left)

45
Q

What is left axis deviation associated with?

A
  • conduction block of anterior branch of left bundle
  • inferior MI
  • LV hypertrophy
46
Q

What is right axis deviation associated with?

A

RV hypertrophy

47
Q

Describe the QRS complex in left axis deviation

A

Upright QRS in lead I and inverted in aVF

48
Q

Describe the QRS complex in right axis deviation

A

Inverted QRS in lead I and upright in lead III or aVF

Semester 2-CVS (18 decks)

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