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Cardiovascular System (Milly's) > ECG- Recognising Common Abnormalities > Flashcards

ECG- Recognising Common Abnormalities Flashcards

1
Q

What are causes of abnormal rhythms? (2)

A

Abnormal impulse formation

Abnormal conduction (AV block)

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2
Q

Where in the heart can rhythms arise from and what are they called?

A

SAN-supraventricular rhythms
Atrium- supraventricular rhythms
AV node- supraventricular rhythms
Ventricle- ventricular rhythms

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3
Q

What are the features of supraventricular rhythms?

A
  • conducted into and within ventricles by His-Purkinje system
  • normal ventricular depolarisation
  • normal (narrow QRS) complexes
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4
Q

What are the features of a ventricular rhythm?

A
  • from foci in ventricle
  • conduction not via usual His-purkinje system
  • depolarisation takes longer
  • wide and bizarre QRS complex (different foci produce different shapes)
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5
Q

What are the 3 types of ventricular rhythms?

A

Ventricular premature beats
Ventricular tachycardia
Ventricular fibrillation

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6
Q

What is atrial fibrillations?

A

Random impulses causing chaotic depolarisation- cardiac cannot contract in a coordinated way

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7
Q

What effect does atrial fibrillation have on CO?

A

It drops it slightly

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8
Q

What is the ECG of atrial fibrillations?

A

No p waves just wavy baseline (atria quiver rather than contract)

Narrow QRS at irregular intervals

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9
Q

What happens to the heart rate and pulse rate during atrial fibrillations?

A

They become irregularly irregular

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10
Q

Why would blood thinners be given to those who have atrial fibrillations?

A

Clots can form in the striatum because there is static blood this can cause strokes etc

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11
Q

What is AV conduction blocks?

A

Delay/failure of conduction of impulses from atrium to ventricles via AV node and bundle of His

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12
Q

What are the two main causes of AV conduction block?

A

Acute MI - full recovery within a few days

Degenerative changes

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13
Q

What are the 3 types of heart blood?

A

First degree block

Second degree heart block: type 1 and type 2

Third degree heart block (complete heart block)

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14
Q

What happens in complete heart block?

A

A pacemaker in the ventricle will take over (ventricular escape rhythm)

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15
Q

What is first degree heart block defined by?

A

Slow conduction in AV node and His Bundle

Normal P wave
Prolonged PR interval (>5 small squares)
Normal QRS

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16
Q

What is type 1, 2nd degree heart block?

A

Progressive lengthening of PR interval until one P is not conducted (this allows time for AVN to recover) then cycle begins again

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17
Q

What is type 2, 2nd degree heart block?

A

PR interval normal
Sudden non-conduction of a beat (dropped beat without warning- ie no QRS)

High risk of progression to complete heart block

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18
Q

What is 3d degree heart block?

A

Atrial depolarisation normal but no impulses are conducted to ventricles

Ventricular pacemaker takes over-wide QRS (ventricular escape rhythm)

No relationship between the P and the QRS wave of an ECG

19
Q

What are the problems with 3rd degree heart block?

A

Heart rate is too slow- 30/40
Too slow to maintain BP and perfusion
Urgent pacemaker insertion required

Possible for someone to go into asystole

20
Q

What are the features of ventricular ectopic beats?

A

Impulses not spread via the His-purkinje system

Much slower depolarisation of ventricles

Wide QRS complex, different in shape to usual

21
Q

What is ventricular tachycardia?

A

Run of 3 or more consecutive ventricular ectopics

Broad complex tachycardia

22
Q

Why is persistence ventricular tachycardia so dangerous?

A

Because the person is at high risk of ventricular fibrillation

They will need to be electrically shocked back into rhythm

23
Q

What is ventricular fibrillation?

A

Abnormal, chaotic, fast, ventricular depolarisation

Caused by impulses form numerous ectopic site in ventricular muscle

No co-ordinated contraction causing ventricles to quiver

24
Q

What effect doe VF have on CO?

A

No cardiac output, cardiac arrest

25
Q

Ischameia and MIs can effect any part of the heart, how can you tell where the damage is?

A

Changes seen in leads facing affected area.

Look at which ECG lead is abnormal

26
Q

What region of tissue in the heart is most vulnerable from lack of perfusion?

A

Sub-endocardial region

27
Q

What changes will you see in an ECG lead facing an area of ischaemic cardiac tissue?

A

ST segment depression
Or T wave inversion

Due to abnormal current during repolarisation

*ischaemic ECG changes may only be seen during exercise but if severe reduction of lumen: ischaemic changes at rest

28
Q

What is STEMI?

A

ST segment elevation myocardial infarction

Due to complete occlusion of lumen by thrombus
Occurs when muscle injury extends ‘full thickness’ from endocardium to epicardium

29
Q

What defines a pathological Q wave?

A

Wider than 1 small square (longer than 0.04 seconds)

Deeper than 2 small squares
(Depth more than 1/4 of the height of the subsequent R wave

30
Q

What effect does hyperkalaemia have on the heart?

A

RMP less negative which inactivates some voltage gates Na+ channels
- heart is less excitable

31
Q

What are the ECG changes seen with hyperkalaemia?

A

High T wave

Prolonged PR interval, depressed ST segment

P wave absent

Ventricular fibrillation

32
Q

What ECG changes are seen in hypokalaemia?

A

Low T wave

33
Q

What is the cardiac axis?

A

The average direction of spread of ventricular depolarisation

Usually Downwards and left
(-30 to +90 degrees)

34
Q

What is left axis deviation?

A

When overall direction of ventricular depolarisation is upwards and to the left (less than -30 degrees)

35
Q

What is left axis deviation associated with?

A

Conduction block of anterior branch of left bundle

Inferior MI

Left ventricular hypertrophy

36
Q

What is right axis deviation?

A

When overall direction of ventricular depolarisation is downwards and to the right (more than +90 degrees)

37
Q

What is right axis deviation associated with?

A

Right ventricular hypertrophy

38
Q

How can you spot left axis deviation?

A

Look at leads I and aVF (or III)

If QRS is upright in lead I an inverted in aVF (or in III), it is LAD

39
Q

How can you spot righ axis deviation?

A

Look at leads I and aVF/III

If QRS is inverted in lead I and upright in lead III (aVF) then it is RAD

40
Q

In an ECG of complete heart block what its he relationship between the P waves and the QRS complex?

A

No relationship between them because the atria and ventricle are being stimulated by different pacemakers

41
Q

What might have happened to cause a widened QRS complex?

A

Problems with ventricle wall, bundle branch block, ischaemia, drugs, metabolic abnormalities, hypokalaemia

42
Q

What do pathological Q waves suggest?

A

Indicates an area of muscle necrosis following ischaemia

43
Q

What does ST depression suggest?

A

Reduced perfusion to the myocardial muscle

44
Q

If a p wave can be seen on an ECG, it is possible for someone to be having AF?

A

No

Cardiovascular System (Milly's) (28 decks)

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