4.5 Bradyarrhythmias

Question 1

What is the criteria for sinus bradycardia?

Answer 1

SA node produces <50 bpm

Question 2

What is sinus node “aging”? Why does it occur?

Answer 2

• Intrinsic heart rate of SA node decreases with age
• This is due to structural and electrical sinus node remodelling

Question 3

Where is the biggest delay in the cardiac electrophysiological cycle?

Answer 3

Between the AV node and the bundle of His.

Question 4

What is shown on the T wave of an ECG?

Answer 4

Ventricular repolarisation

Question 5

What two common conditions can cause sinus bradycardia? What are two less common causes?

Answer 5

Common:
- Decreased sympathetic tone
- Increased vagal tone
Less Common:
- Medications
- Sinus node dysfunction

Question 6

Describe respiratory sinus arrythmia

Answer 6

• HR increases during inspiration
• HR decreases during expiration

Question 7

Define sinus arrythmia. Can it ever be physiologically normal?

Answer 7

• Phasic variation in cycle length
• Normal (resp. sinus arrythmia)

Question 8

What abnormal rhythms are encompassed within sick sinus syndrome

Answer 8

• Persistent sinus bradycardia
• Sinus arrest or exit block
• Combination of SA and AV node abnormalities
• Tachybrady syndrome

Question 9

What are some factors that can cause sinus node disease?

Answer 9

• Fibrosis in proximity to SAN and atrial scar (although not always)
• Nodal-atrial discontinuity
• Inflammatory/degenerative changes
• Ion channel remodelling

Question 10

What is an atrioventricular block?

Answer 10

Atrial impulse is delayed or not conducted into ventricles

Question 11

What are the four categories of AV block?

Answer 11

1st Degree: Impulses are conducted but conduction time is prolonged
2nd Degree Type 1 Mobitz: Progressive lengthening until an impulse is not conducted. Then repeats.
2nd Degree Type 2: Intermittent block of conductoin with no prior lengthening of conduction time
3rd Degree (Complete): No association between atria and ventricles

Question 12

Which types of AV block require urgent intervention?

Answer 12

2nd Degree Type II
3rd Degree

Question 13

For which patients are pacemakers indicated?

Answer 13

Symptomatic bradycardia

Question 14

What are the three configurations of cardiac pacemaker devices?

Answer 14

• Single chamber (right atrium only)
• Dual chamber (Right atrium and right ventricle)
• Biventricular, used in heart failure (RA, both ventricles)

Question 15

What is the main tool used to diagnose bradyarrhythmia?

Answer 15

ECG