12.3 Clinical Electrophysiology

Question 1

Why is an electrocardiogram (ECG) good?

Answer 1

• Cheap
• Quick
• Non-invasive
• Can help diagnose cardiac and non-cardiac conditions

Question 2

Draw a normal ECG

Answer 2

Question 3

Where do the limb leads go?

Explain how lead I, II, III work

Answer 3

• Right arm (RA)
• Left arm (LA)
• Right leg (RF)
• Left leg (LF)

LEAD III goes Left arm to Right leg

Question 4

Draw where the chest leads go

Answer 4

Question 5

Explain the waves in an ECG and label the heart for where each section takes place

Answer 5

Question 6

Explain how to read the timing of an ECG on the strip

Answer 6

• The paper strip shows electrical activity over time-
  
  • 5 small squares 200ms
  • 5 big squares 1 second
  • One standard ECG strip- 10 seconds

Question 7

Explain (diagram) the different areas on an ECG strip

Answer 7

Question 8

Explain where the chest leads point to in the heart

Answer 8

Question 9

Explain where on an ECG you would see areas of the heart

Answer 9

• In the chest leads section

Question 10

What do you check for in an ECG analysis?

Answer 10

1. Check details
2. Rate
3. Rhythm
4. Axis (refers to the overall electrical direction within the heart)
   
   • Towards an electrode is POSITIVE
   • Away from an electrode is NEGATIVE
5. The alphabet (P, PR interval, QRS complexes, ST segment, T waves, QT interval)

Question 11

How do you work out rate (heart) on an ECG strip?

Answer 11

Rate = Total number of R waves x 6 (on a standard 10sec strip)

Rate = 300 / number of large squares between R waves

Question 12

What is a normal heart rate (too low/too high meaning)?

Answer 12

Normal heart rate = 60-100bpm

>100bpm = tachycardia

<60bpm = bradycardia

Question 13

What do you check for in terms of rhythm on an ECG?

Atrial fibrillation & atrial flutter tell tell signs?

Answer 13

• For it to be normal sinus rhythm
  
  • Normal looking P wave
  • Always followed by a QRS
  • In a regular fashion

Question 14

What happens in atrial fibrillation? (ECG)

Answer 14

• IRREGULARLY IRREGULAR QRS complexes
• NO P waves (no SA node stimmulation)

Question 15

What happens in atrial flutter? (ECG)

Answer 15

Can have different types of blocking e.g. 2:1 block (R waves 2 big squares apart), 3:1 block (R waves 3 big squares apart

Question 16

Explain complete (third degree) AV block on an ECG

Answer 16

Atrioventricular block = Conduction (communication) between the atria and ventricles of the heart is impaired

• Rate about 35bpm
• Regular QRS complexes
• There are p-waves BUT…
• No relationship between p-waves and QRS complexes, more Ps than Qs

Question 17

What is first degree heart block?

Answer 17

• The impulse is delayed at the AV node and PR interval >0.2seconds (same amount of time always) (regularly irregular)

Question 18

What is second degree heart block?

Answer 18

Mobitz Type 1

• PR interval will become greater* and *greater* until there will be a *dropped QRS complex and there are two consecutive P waves, after which the pattern will restart
• ​*Mobitz Type 2
• PR and R to R intervals will remain consistent, but there will be “missing” QRS complexes (always come back in a pattern e.g. miss, seen, seen, miss, seen…)
• Is more serious

Question 19

Explain what happens on an ECG in ventricular tachycardia (& show how it would be seen on an ECG)

Answer 19

• Regular tachycardia, rate ~150bpm
• Broad QRS complexes
• No obvious preceding atrial activity

Question 20

What are the types of axis & show how they would be seen on an ECG (lead I & II)?

Answer 20

Question 21

Explain what is left axis deviation

Answer 21

• Look at leads I, II, III
• If lead I is positive, II is middling/negative and III negative, there is left axis deviation
• The deflections are Leaving each other in Left axis deviation

Question 22

Explain right axis deviation

Answer 22

• Lead I is more negative, and III is positive, it is right axis deviation
• Lead I and Lead III are Reaching toward each other in Right axis

Question 23

What conditions can cause left axis deviation?

Answer 23

1. Early conduction disease
2. Myocardial Infarction
3. Atrial Septal Defect
4. Obesity
5. Wolff-Parkinson White

Question 24

What conditions can cause right axis deviation?

Answer 24

1. Myocardial Infarction
2. RV strain-
   
   1. Pulmonary (COPD, PE, pulmonary hypertension
   2. Cardiac- RV cardiomyopathy, WPW

Question 25

What are the different types of P waves (abnormal)?

Answer 25

* Normal * Right **atrial enlargement** (*pulmonale*) - big P wave * Left **atrial enlargement** (*mitrale*) - 2 P waves

Question 26

What could a **prolonged PR interval** mean?

Answer 26

**1st degree heart block** (if more that 0.2secs)

Question 27

How does a contraction of the heart take place? (impulse)

Answer 27

1. The heart's primary impulse generator is the **sinoatrial (SA)** node located in the *right atrium.* 2. The impulse is carried through the *cardiac muscle tissue* of the *atria*. 3. This causes the *atria* to **contract**. 4. The impulse then travels through the network to the *ventricles* causing them to contract. 5. The resulting action causes blood to be pumped through the body via connecting blood vessels.

Question 28

What is **left bundle-branch block (LBBB)** (&how is it seen on ECG)?

Answer 28

Question 29

What is **right bundle-branch block**? (RBBB)

Answer 29

Question 30

What **abnormalities** could be seen in the **ST segment** & what these could mean?

Answer 30

* **ELEVATION** * *Infarction* * *Pericarditis* * **DEPRESSION** * *Ischaemia*

Question 31

What **abnormalities** can be seen in the T wave?

Answer 31

* **FLAT/PROLONGED** T wave = **LOW K+** * **PEAKED** = High K+/early MI * **INVERSION** = Ischaemia

Question 32

Explain how the **QT interval** is measured

Answer 32

* Is **longer** in **women**