Anti-Arrythmic Drugs

Question 1

Which classes of drugs are used for a long excitable gap?

What is an alternative therapy

Answer 1

Class I - Na channel blockers
Class IV - Ca channel blockers
Overdrive pacing

Question 2

Procainamide
Class
Function
ECG

Answer 2

Class Ia
Acts on Na channels w/ intermediate recovery.
Ikr –> longer refractory period
Widens QRS and lengths QT

Question 3

Lidocaine
Class
Function
Tx

Answer 3

Class Ib
Acts on Na channels w/ rapid recovery
Shortens APD, which reduces risk of reentry. Also increases threshold
Tx VT in acute setting

Question 4

Flecainide
Class
Function
ECG
Tx
Contraindication

Answer 4

Class Ic
Acts on Na channels w/ slow recovery.  
Slows phase 0
Widens QRS
Tx A fib (mainly).  
Do NOT use post-MI to decrease PVCs --> higher mortality

Question 5

What is contraindication for Class I drugs?

Answer 5

CAD or CHF

Question 6

BBs
Mechanism
ECG
3 drugs used and selectivities

Answer 6

Lengthens phase 4 via inhibiting If
Prolongs AVN conduction
Lengthens PR interval
Propranolol (nonselective)
Metoprolol / atenolol are both B1 selective

Question 7

4 class III drugs

Answer 7

Amiodarone, Dofetilide, Sotalol, Droneterone

Question 8

Class IV drugs
Function
ECG
2 drugs

Answer 8

Non-dihydropyridine CCBs
Slow rate of phase 4 and slows conduction through AVN
Prolongs PR interval
Verapamil and Diltiazem

Question 9

Adenosine
Mechanism
Use

Answer 9

Gi inhibits L-type Ca channels and activates GIRK (Ach-sensitive K channel)
Slows phase 4, AVN conduction, and AVN refractory period
Shortens APD
Short half life
Used in ER when pas go into SVT (AVNRT or AVRT). Causes PAC or PVC to interrupt circuit

Question 10

Tx A Fib / Flutter
How is ventricular rate slowed?
How is atrial rate slowed?
Others

Answer 10

Cardioversion in cases of rapid ventricular response
•Slow ventricular rate by slowing AV node w/ BBs, CCBs, or digoxin
•Slow atrial conduction w/ Ia (procainamide), Ic (flecainide), or III (dofetilide / amiodarone).
•Aspirin and / or warfarin

Question 11

Tx AVNRT
1st line
Acute
Chronic

Answer 11

• Vagal maneuvers are 1st line of treatment
• Acute– Adenosine slows AV nodal conduction and can trigger PAC or PVC to block reentry. May also use BBs or CCBs
• Chronic – BBs, CCBs, digitoxin

Question 12

Tx AVRT
1st line
Acute
Chronic

Answer 12

• Vagal maneuvers are 1st line tx
• Acute – adenosine (slows AVN), CCBs, BBs
• Chronic – ablation of accessory pathway is tx of choice. Otherwise use BBs or CCBs in addition to Ia, Ic, or III

Question 13

Tx Sinus Bradycardia
Emergent
Chronic

Answer 13

Acute - IV atropine, catecholamines, or pacemaker

Chronic - Correct electrolyte imbalance or pacemaker

Question 14

Tx VT / VF during acute MI
Emergent
Acute
Chronic

Answer 14

•Emergent – cardioversion
•Acute – Lidocaine (Ib) is 1st choice. Amiodarone is 2nd choice.
Chronic - BB. ICD w/ defetilide or amiodarone

Question 15

Tx VT w/ chronic LV systolic dysfunction
Emergent
Acute
Chronic

Answer 15

• Emergent – cardioversion
• Acute – IV amiodarone
• Chronic – ICD combined w/ amiodarone or dofetilide

Question 16

Tx Torsades
Emergent
Chronic long QT

Answer 16

• Emergent – Shorten APD by treating hypokalemia / hypomagnesia. Increaing HR via pacing or adrenergic agonist (isoproterenol) –> decreased APD. Cardioversion only causes brief respite.
• Chronic long QT – Use pacemaker to avoid bradycardia. Tx ischemic heart disease. ICD.