Cardiac Classes

Question 1

Class 1a antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 1

Mechanism

• Block Myocyte Phase 0 Na+ influx (depolarisation)
• Sodium blocker
• Intermediate half life

Examples

• Quinidine
• Procainamide
• Disopyramide

Uses

• SVT, VT

Question 2

Class 1b antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 2

Mechanism

• Block Myocyte Phase 0 Na+ influx (depolarisation)
• Sodium blocker
• Fast half life/ weak

Examples

• Lidocaine
• Phenytoin

Uses

• MI associated VT

Question 3

Class 1c antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 3

Mechanism

• Block Myocyte Phase 0 Na+ influx (depolarisation)
• Sodium blocker
• Slow half life/ strong

Examples

• Flecainide

Uses

• Rhythm control

Question 4

Class 2 antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 4

Mechanism

• Block sympathetic adrenergic input
• Slowing Nodal Phase 0
• B-blockers

Examples + Uses

• Carvedilol - HF Sotalol (2+3) - 1st Rhythm control
• Atenolol - Rate control, MI, Stable Angina (4th), SVT (3rd)
• Bisoprolol - Stable Angina (4th)
• Metoprolol - Stable Angina (4th)
• Propanolol - Migraine prophyl
• Last stage of hypertension

Question 5

Class 3 antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 5

Mechanism

• Block Myocyte Phase 3 K+ efflux
• Potassium blocker

Examples + Uses

• Sotalol (2+3) - 1st Rhythm control
• Amiodarone - Rhythm control, 1st VT (stable)

Question 6

Class 4 antiarrhythmic

• Mechanism
• Examples
• Uses

Answer 6

Mechanism

• Non-DHP Calcium ‘SLOW’ channels
• Nodal Phase O (-ve chronotrope)
• Myocyte Phase 2 (-ve inotrope)

Examples + Uses

• Rate control (Diltiazem> Verapamil)
• SVT(2nd)/ asthmatic (Verapamil)
• Angina 4th (Diltiazem, Verapamil)
• Angina 5th Duo (DHP: Nifedipine mod. release + B-blocker)
• Reynauds (Diltiazem + DHP: Nifedipine)
• Cluster prophyl (Verapamil)

DHP CCB are not Class 4 antiarrhythmics.

Question 7

Cardiac Glycosides

• Mechanism
• Examples
• Uses

Answer 7

Mechanism

1. ++Parasympathetic to SA node (-chronotrope)
2. ++NaCa exchange, increasing intracellular Ca and force of contraction (+inotrope)

Example + Use

• Digoxin - Rate control(2)

Question 8

Adenosine

• Mechanism
• Uses

Answer 8

Mechanism

• Opens Nodal K+ INFLUX -> HyPERpolarisation
• Short half life
• C: Total stop

Uses

• Narrow Complex Tachy/ SVTs (stable)
  
  • (asthmatic: Verapamil)

Question 9

Magnesium Sulphate Indications

Answer 9

MgSO₄ uses

• Torsades de Pointes
• Hypomagnesium
• Asthma: Severe Exacerbation
• Pre-Eclampsia: Severe/ neuro signs

Question 10

Magnesium Sulphate

• Signs of Toxicity
• Management of Toxicity

Answer 10

Toxicity Signs

• Loss of reflexes ← Monitor every 4-6hrs
• Flushing
• Double vision
• Slurred speech

Treatment

• Stop MgSO4 infusion
• Calcium gluconate → relieves vascular spasm

Question 11

Atropine

• Mechanism
• Uses

Answer 11

Mechanism

• Anti-muscarinic Inhibits parasympathetic input to NODES

Uses

• Bradycardia

IM/SC - initial M1 presynaptic block prevents reuptake⇒ bradycardia