Antiarrhythmic agent resident survival guide

c Template:Antiarrhythmic agent Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Priyamvada Singh, M.D. [2]

Vaughan-Williams classification of antiarrhythmic agents

Vaughan-Williams classification of antiarrhythmic agents

Class IA

Class IB

Class IC

Class II

Class III

Class IV

Mechanism

Predominantly sodium channel blocker with some potassium channel blocking activity

Sodium channel blocking activity

Sodium channel blocking activity

*Pure α1 agonist(Vasoconstrictive) *No β1

*Predominant β1 agonist (↑contractility) *β2 arterial smooth muscle (Hypotensive)

Agents

Quinidine, procainamide, disopyramide

Lidocaine, mexiletine, phenytoin

Flecainide, propafenone

1st line Neurogenic shock 3rd-4th line septic shock

*1st line cardiogenic shock * low output septic shock

Effect

Slows conduction, & prolongs repolarization

Slow conduction in diseased tissues, shorten repolarization

0.03 unit/min

20-300 mcg/kg/min

2.5-20 mcg/kg/min

Indications

Pre-excited atrial arrhythmias PSVT, Ventricular tachycardia

Ventricular arrhythmia

*Coronary spasm *Splanchnic vasoconstriction

Reflex bradycardia (only α1)

Hypotension (β2)

Complications

Quinidine - abdominal cramping, diarrhea, rash, cinchonism (hearing decrease, tinnitus, and blurred vision), thrombocytopenia, hemolytic anemia, lupus syndrome , granulomatous hepatitis, QRS widening and ventricular arrhythmias.

CNS side-effects such as peri-oral numbness, tremors, paraesthesia, diplopia, hyperacusis, slurred speech, altered consciousness, seizures, and coma can be seen. Proarrhythmia and gi side-effects are common.

*Ischemic heart *Gut ischemia

*Bradycardia *Heart block

*Hypotension (add α1 agonist)

Do's

• Class IA agents are proarrhythmogenic and are associated with increased incidences of Torsade de Pointes, ventricular tachycardia or ventricular fibrillation. If arrhythmia are observed with one class 1A agent all other class 1A agents should be avoided. Due to risk of proarrhythmia all class 1A drugs should be initiated in hospital. If QTC > 500 msec the drug should be stopped.
• Disopyramide side-effects include anticholinergic effects (30%) including dry mouth, blurred vision, constipation, and urinary retention. Pyridostigmine (90 mg twelve hourly to 180 mg every eight hours) prevents or diminishes the anticholinergic effect of disopyramide and allows high tolerated doses of the drug.
• Disopyramide-induced hypoglycemia has been noted. Other reported side effects includes nausea, vomiting, rash, cholestatic jaundice, and agranulocytosis. It prolongs repolarization and may cause proarrhythmia (VF, Torsade de Pointes)
• Procainamide has side-effects similar to Quinidine.

Don'ts

• Do not start with low dose Dopamine dose to perfuse the kidney.