Atrioventricular (AV) Block

Question 1

Definition of 1st degree heart block

Answer 1

• Delayed AV conduction through the AV node
• Every impulse leads to ventricular contraction

Question 2

ECG findings of 1st degree heart block

Answer 2

• PR interval greated than 0.2s

Question 3

Definition of 2nd degree heart block - Mobitz type 1/Wenckebach’s

Answer 3

• Atrial impulse becomes gradually weaker until it does not pass through the AV node
• After failure the impulse becomes strong again and the cycle repeats

Question 4

ECG findings of 2nd degree heart block - Mobitz type 1/Wenckebach’s

Answer 4

• Increasing PR interval until P wave no longer conducts to ventricles
• PR interval then returns to normal and the cycle starts again

Question 5

Definition of 2nd degree heart block - Mobitz type 2

Answer 5

• Intermitted failure of interruption of AV conduction
• Usually a set ratio of P waves to QRS complexes
• PR interval remains normal
• Risk of asystole

Question 6

ECG findings of 2nd degree heart block - Mobitz type 2

Answer 6

• Normal PR interval with occasional missing QRS complexes at regular intervals

Question 7

Definition of 3rd degree heart block/complete heart block

Answer 7

• No relationship between P waves and QRS complexes
• Risk of asystole

Question 8

Treatment of AV Block

Answer 8

• Stable
  
  • Observe
• Unstable or risk of asystole
  
  • Atropine (up to 6 doses)
  • Other inotropes (i.e noradrenaline)
  • Transcutaneous cardiac pacing
  • Permanant pacemaker sometimes required

Question 9

Side effects of atropine

Answer 9

• Pupil dilatation
• Urinary retention
• Dry eyes