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Flashcards in Week 7 Deck (63)
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1
Q

Which direction is Q wave deflection?

A

downwards

2
Q

What does the Q wave represent?

A

septal depolarisation (left to right)

3
Q

Which leads are septal Q waves seen in?

A

Leads looking at the left side of the heart (I, II, aVL, V5 and V6)

4
Q

What are the 3 characteristics of pathological Q waves

A

More than 2mV amplitude or 0.04 seconds long

5
Q

What should you consider if you see pathological Q waves?

A

(1) myocardial infarction, (2) LV hypertrophy, (3) bundle branch block (4) pulmonary embolism (if Q wave in lead III).

6
Q

In many cases do pathological Q waves become permanent following MI?

A

90%

7
Q

Can myocardial infarctions be asymptomatic?

A

yes - 20% are silent

8
Q

What are the symptoms of a MI?

A

chest pain, pain in left arm and jaw, sweating, nausea

9
Q

Is ST segment elevation an ECG characteristic of MI?

A

Yes

10
Q

Explain how MI leads to pathological Q waves

A

MI causes necrosis of myocardium which can no longer conduct electrical activity. Leads ‘look through’ necrotic tissue and since electrical activity moves from the inside to the outside of the heart, a negative deflection is detected.

11
Q

A MI that produces a pathological Q wave is what type of MI?

A

Transmural

12
Q

Is a subendocardial or transmural MI more serious?

A

Transmural - damage to all layers of the heart

13
Q

What 4 questions should you ask about QRS complex?

A
  1. are R/S wave too tall? 2. are QRS complex too small? 3. are QRS complex too wide? 4. are QRS abnormal shape?
14
Q

The deepest R and S wave should exceed how many mm?

A

25mm (2.5 large squares)

15
Q

The R wave increases in height between V1 and V6?

A

True

16
Q

Is the R wave smaller than the S wave in V1 and V2

A

True

17
Q

Is the R wave smaller than the S wave in V5 and V6?

A

False

18
Q

What waves are high/deep in LVH?

A

Leads that look at the heart from the left (I, II, aVL, V5 and V6) have high R waves and the reciprocal (leads that look at the heart from the right) V1 and V2 have deep S waves

19
Q

What criteria must be met for LVH?

A

V5/6 R wave > 25mm, V1/2 S wave > 25mm or V5/6 + V1/2 = > 35mm

20
Q

Can young, thin people exceed LVH ECG criteria? Does it mean they have LVH?

A

Yes - doesn’t diagnose LVH - echocardiogram necessary

21
Q

What might cause pathological LVH?

A

hypertension

22
Q

In what ways is LVH detrimental?

A

Chamber narrows inwards as well as outwards and reduces chamber size - reducing CO

23
Q

What has to be present for LVH/RVH to be associated with ‘strain’?

A

ST segment depression and T-wave inversion

24
Q

What ECG change does RVH cause?

A

dominant R wave in V1

25
Q

What is RVH associated with?

A

(1) right axis deviation, (2) RBBB

26
Q

How is a dominate R wave in V1-V3 associated with WPW?

A

In a left-sided WPW you typically see right axis deviation and so a dominant R wave as electrical activity flows towards the right side of the heart

27
Q

How is a dominant S wave in V1-V3 associated with WPW?

A

In right-sided WPW you typically see left axis deviation and so a dominant R wave as electrical activity flows away from the right side of the heart

28
Q

Are dominant R waves seen in posterior wall MI?

A

Yes - reciprocal appearance in anterior chest leads of typical MI changes - so pathological Q wave is seen as R wave.

29
Q

Reasons for small QRS?

A

Reduced electrical activity recording: (1) obesity, (2) emphysema, (3) pericardial effusion (excess fluid in pericardial cavity)

30
Q

Minimum length of ventricular depolarisation?

A

0.12 seconds (3 small boxes)

31
Q

What does a wide QRS typically mean?

A

Conduction through the ventricles was slower than normal

32
Q

What are three causes of wide QRS?

A

(1) bundle branch block, (2) ventricular ectopic, (3) hyperkalaemia

33
Q

Does a bundle branch block lead to indirect depolarisation by other bundle branches?

A

Yes

34
Q

What is a hemi-block?

A

Block of the left anterior fascicle or left posterior fascicle

35
Q

What happens during v. depolarisation with bundle branch block

A

Ventricles are depolarisation by myocyte-myocyte conduction

36
Q

What leads are used to determine a LBBB or RBBB?

A

V1 and V6

37
Q

What is the acronym used?

A

WILLIAM MORROW

38
Q

What is seen in V1 in RBBB?

A

(1) positive septal R wave, (2) S wave (LV dep), (3) R prime (late RV dep).

39
Q

What is seen in V6 in RBBB?

A

(1) negative septal Q wave, (2) R wave (LV dep), (3) wide S wave (late RV dep).

40
Q

Is LBBB an EECG contra-indication?

A

Yes

41
Q

What is LBBB an EECG a contra-indication?

A

The ECG beyond QRS complex cannot be read

42
Q

What is PVC?

A

Ectopic beat originating outside the conduction system

43
Q

What is bigemy?

A

PVC after every 2nd normal QRS

44
Q

What is trigemy?

A

PVC after every 3rd normal QRS

45
Q

What may cause PVC’s?

A

Anything that disrupts electrolyte balance

46
Q

Why are PVC’s important?

A

(1) they can lead to more serious arrhythmias (2) they decrease CO (particularly if they frequent - reduced ventricular filling)

47
Q

Which direction is the T-wave deflected in premature beat (PVC)?

A

opposite of QRS complex

48
Q

Are P-wave present in PVC?

A

Usually absent but retrograde conduction may depolarise the atrial and distort the ST segment

49
Q

Can you measure the PR and QT intervals on premature beat?

A

No

50
Q

What is the R-on-T phenomena

A

When a PVC strikes on the downstroke of previous T wave and can trigger more serious rhythm disturbances

51
Q

What is seen after a PVC?

A

Compensatory pause - time between two normal QRS is doubled

52
Q

A PVC that is not followed by a compensatory pause is referred to as what?

A

Interpolated

53
Q

Why is a compensatory pause seen?

A

the ventricular myocardium is in refractory and cannot be depolarised

54
Q

PVC that look alike are what?

A

Uniform

55
Q

If PVC’s are uniform they likely originate from the same ectopic focus? T/F?

A

True

56
Q

What are two PVC’s in a row called?

A

Couplet

57
Q

Why can two PVC’s in a row cause ventricular tachycardia?

A

Because they meet refractory tissue

58
Q

What is multiform PVC

A

PVC that look different as they originate from different foci or same sight with different conduction

59
Q

What are dangerous PVC’s?

A

(1) R-on-T PVC, (2) paired, (3) trigemy, (4) bigamy, (5) multiform

60
Q

is the pulse after a PVC stronger or weaker?

A

Weaker

61
Q

What should you consider if you see a slurred or notched QRS?

A

(1) WPW, (2) hemi-block (3) incomplete bundle branch block

62
Q

LBBB V1 characteristics

A

(1) Q wave (septal depolarisation from right to left), (2) R-wave from normal RV dep (3) S wave from late LV dep

63
Q

LBBB V6 characteristics

A

(1) R wave (septeal depolarisation from right to left) (2) S-wave from normal RV dep (3) R-wave from late LV dep