Arrhythmias

Question 1

What are the sort of abnormal heart rates and rhythms that you can get?

Answer 1

• bradycardia
• atrial flutter
• atrial fibrillation
• tachycardia:
  Can cause
  1. Ventricular tachycardia
  2. Supraventricular tachycardias
  -ventricular fibrillations

Question 2

What are the causes of tachycardia? (4)

Answer 2

1. Ectopic pacemaker activity: damages area becomes depolarised and spontaneously active, latent pacemaker region activated due to ischaemia (dominates over SA node)
2. Afterdepolaristion: abnormal depolarisation following the action potential (triggered activity)
3. Atrial flutter/atrial fibrillation
4. Re-entry loop: conduction delay, accessory pathway

Question 3

What are the causes of bradycardia? (2)

Answer 3

1. Sinus bradycardia: sick sinus syndrome (intrinsic SA node dysfunction), extrinsic factors such as drugs that slow down the AV node conduction (ie Beta blocker, some Ca2+ channel blockers)
2. Conduction block: problems at AV node or bundle of His, slow conduction at AV node due to extrinsic factors (beta blockers, some Ca2+ channel blockers)

Question 4

What is delayed after-depolarisation (triggered activity)?

Answer 4

• Delayed after-depolarisations
• more likely to happen if there is intracellular ca2+ high
• random depolarisation after an action potential, can cause tachycardia

Question 5

What is early after-depolarisations (triggered activity)?

Answer 5

• a premature depolarisation (usually during the action potential)
• can lead to oscillations, ventricular tachycardia
• more likely to happen if AP is prolonged
• longer AP (from drugs etc) =longer QT interval

Question 6

What is AV nodal re-entry? ****

Answer 6

When there are fast and slow pathways in the

Question 7

What are the 4 basic classes of anti-arrhythmic drugs?

Answer 7

1. Drugs that block voltage-sensitive sodium channels
2. Antagonists of beta- adrenoreceptors antagonists
3. Drugs that block. K+ channels
4. Drugs that block Ca2+ channels

Question 8

What is a limitation of drugs that block voltage dependant Na+ channels?

Answer 8

Only blocks Olathe gates Na+ channels in open or inactive state therefore potentially blocks damaged depolarised tissues

Question 9

Give an example of a Na+ voltage dependant channel blocking drugs (class 1 drugs)?

Answer 9

Lidocaine

Question 10

Give some examples of b-adrenoreceptors antagonists (class 2)?

Answer 10

Propranolol, atenolol

Beta blockers