Antiarrhythmic agent resident survival guide
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Life Threatening Causes
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) |
|*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|
|Reflex bradycardia |
|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 |
|*Hypotension (add α1 agonist)|
- 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.
- Do not start with low dose Dopamine dose to perfuse the kidney.