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Y3 MOD Cardiology > Approach to ECGs > Flashcards

Approach to ECGs Flashcards

1
Q

Define what an ECG is

A

The ECG is a recording of changes in electrical potential difference occurring during the depolarisation and repolarisation of the myocardium plotted against time. i.e. It is a Voltage - Time Graph

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2
Q

The P wave is the sum of … ?

A

All the atrial action potentials (depolarisation)

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3
Q

What acts as the pacemaker within the heart?

A

Sinoatrial node

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4
Q

The slowed conduction through the AV node permits…?

A

Ventricular filling which allows the atria to completely contract before depolarisation

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5
Q

The QRS complex is shown on the ECG due to?

A

Rapid ventricular depolarisation

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6
Q

The T wave represents?

A

Ventricular repolarisation

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7
Q

The ECG electrodes are colour coded (UK scheme) and attached to:

  • Red
  • Yellow
  • Green
  • Black
A

Red: Right Fore
Yellow: Left Fore
Green: Left Hind
Black: Right Hind (the “earth lead”)

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8
Q

The most important ECG lead to examine is? Why?

A

LEAD II – this usually shows the largest complexes in the dog and cat. All measurements are made from this.

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9
Q

Lead I, II and III connect?

A 
I = RF and LF
II = RF and LH
III = LF and LH
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10
Q

What questions need to be asked when looking at any ECG?

A
  • What is the HR?
  • Are the R-R intervals regular, regularly irregular or chaotically irregular ?
  • Is there a P wave preceding every QRS complex and a QRS complex following every P wave?
  • Do the QRS complexes look normal (i.e. using the His-Purkinje system normally?)
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11
Q

Sinus arrhythmia can be normal in which species?

A

Dog

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12
Q

When would periods of sinus arrest of up to 5 seconds be normal?

A

In sleeping dogs

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13
Q

In which species is sick sinus syndrome most commonly seen?

A

Westies

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14
Q

Which monitor can be used to investigate collapse and periods of sinus arrest?

A

Holter monitors

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15
Q

A prolonged P wave on the ECG represents?

A

Left atrial enlargement

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16
Q

A tall P wave on the ECG represents?

A

Right atrial enlargement

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17
Q

A tall R wave on the ECG represents?

A

Left ventricular enlargement

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18
Q

A prolonged QRS complex on the ECG represents?

A

Ventricular enlargement / hypertrophy

19
Q

How would first degree AV block appear on an ECG?

A

The P:QRS ratio remains 1:1, but the P-R (PQ) interval is longer than normal for the species. This may be due to high vagal tone, the effect of certain drugs (e.g.
digoxin) or disease.

20
Q

How would second degree AV block appear on an ECG?

A

There are some P waves not followed by QRS complexes, the QRS complex should look normal. The P-R interval varies,
and tends to lengthen beat to beat.

21
Q

How would third degree AV block appear on an ECG?

A

The P waves bear no relationship to the QRS complexes. The P waves occur at their own, normal rate and the QRS complexes arise due to much slower automaticity of the Purkinje system or ventricular myocardium.
T waves are oppositely directly.

22
Q

T waves which go in the opposite direction are also known as?

A

Ventricular escape complexes

23
Q

How would atrial fibrillation appear on an ECG?

A

• QRS complexes and T waves look relatively normal, but the rate is fast and the interval between them (R-R interval) is highly variable (chaotic).
• There are no P waves (fibrillation waves may be seen along the baseline, but are not
always evident).

24
Q

What are some possible systemic causes of ventricular premature complexes?

A
  • Gastric dilatation volvulus
  • Splenic lesions / splenectomy
  • Sepsis
  • Pancreatitis
  • Pyometra
  • Thoracic trauma (myocardial contusions)
  • CNS lesions
25
Q

How can a morbitz type I and II degree AV block be distinguished?

A

Type 1: Variable P-R interval before “dropped” P wave
Type II: Constant P-R interval (may be normal)
- Fixed ratio of P waves: QRS complexes

26
Q

Interpret and diagnose the following ECG findings:

  • HR 220 bpm
  • Normal QRS (using His-Purkinje system)
  • Chaotically irregular R-R intervals
  • No discernible P waves – irregular baseline
A

Atrial fibrillation

27
Q

How would supraventricular tachycardia present on an ECG?

A

May be very fast (>300 bpm), but regular PQRS complexes

28
Q

Which ECG lead is used for standard measurements in dogs and cats?

A

Lead II

29
Q

If the QRS duration is longer than 0.06s, what is indicated?

A

Ventricular hypertrophy

30
Q

What are some possible causes of dampened QRS complexes?

A
  • Conformation (massive breed)
  • Fat
  • Pleural effusion
  • Pericardial effusion
  • Thoracic mass
31
Q

Left ventricular enlargement can be assessed by looking at which part of the ECG?

A

R wave height

32
Q

A prolonged P wave duration is an indicator of…?

A

Left atrial enlargement

33
Q

On an ECG, what can be seen which may indicate atrial stretch?

A

Supraventricular premature complex: Normal QRS complex, premature

34
Q

Describe where the following ECG changes show enlargement at different points of the heart?

  1. Prolonged P wave
  2. Tall P wave
  3. Tall R wave
  4. Prolonged QRS
A
  1. Left atrial enlargement
  2. Right atrial enlargement
  3. Left ventricular enlargement
  4. Left ventricular enlargement
35
Q

What is the ECG used for in large animals?

A

To document cardiac rhythm

36
Q

How does a left bundle branch block appear on an ECG?

A
  • Normal P:QRS ratio
  • Tall, wide QRS complexes, T waves on opposite direction
  • QRS duration > 0.08 seconds
37
Q

How does a right bundle branch block appear on an ECG?

A
  • Normal P:QRS ratio
  • Deep, wide S waves, so –ve QRS complex, T waves on opposite direction
  • QRS duration > 0.08 seconds
38
Q

What does the QT interval represent?

A

Total time for ventricular depolarisation and repolarisation

39
Q

The QT interval is dependant on?

A

Heart rate (increased QT interval with slower heart rate)

40
Q

What other factors can affect the QT interval?

A
  • Hypocalcaemia
  • Vomiting and diarrhoea
  • Hypothermia
  • Dehydration
41
Q

Changes in T waves are indicative of?

A

Metabolic changes

42
Q

How will hyperkalaemia affect an ECG?

A
  • Tall spikey T waves
  • Atrial standstill: no P waves
  • Variable R-R interval
43
Q

On an ECG, the ST segment represents?

A

The period between depolarisation and repolarisation

44
Q

ST segment coving (slurring) indicates …?

A

Left ventricular hypertrophy
and/or
Myocardial hypoxia

Y3 MOD Cardiology (7 decks)

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