The Action Potential Phase 1 30 mv Phase 2 0 mv Phase 0 Phase 4 90 mV
The Action Potential Phase 0 Phase 4 Phase 3 Phase 2 Phase 1 - 90 mV 0 mV 30 mV
Class I Na+ Channel blockers IA-Quinidine/Procainamide/Disopyramide IB- Lidocaine/Mexiletine/Phenytoin IC-Flecainide/Propafenone/Ethmozine 2 Affects 0 Phase o ERP RRP
Class I Na+ Channel Blockers • IA - Quinidine/Procainamide/Disopyramide • IB - Lidocaine/Mexiletine/Phenytoin • IC - Flecainide/Propafenone/Ethmozine 1 0 2 3 4 ERP RRP Affects Phase 0
Class A- Na+ Channel Blockers Procainamide/Quinidine/Disopyramide Mode of action Depress conduction and prolong refractoriness Atrial, His-Purkinje, ventriculartissue Peripheral alpha block Vagolytic Negative inotrope ECG changes ncrease PR, QRS (Diso:PR个>QRs个) Toxicity: QTc increases by 30% or QT>0.5 sec Ca* channel blockade potent anticholinergic (Diso)
Class IA - Na+ Channel Blockers Procainamide/Quinidine/Disopyramide • Mode of action – Depress conduction and prolong refractoriness • Atrial, His-Purkinje, ventricular tissue – Peripheral alpha block – Vagolytic – Negative inotrope • ECG changes – Increase PR, QRS (Diso: PR > QRS ) – Toxicity: QTc increases by 30% or QT > 0.5 sec – Ca++ channel blockade / potent anticholinergic (Diso)
ClassA- Na+ Channel Blockers procainamide Uses SVT(reentry) or VT Afib/flutter (on digoxin) Drug interactions-Decrease metabolism of Amiodarone Dose IV: load 15 mg/kg over 1 hour, then 30-80 ug/kg/min (level 5-10 ng/ml) PO: 30-70 mg/kg/day Side effects: Lupus- in slow acetylators ANA+: 50-90% Symptoms: 20-30%
Class IA - Na+ Channel Blockers Procainamide • Uses – SVT (reentry) or VT – Afib/flutter (on digoxin) • Drug interactions-Decrease metabolism of Amiodarone • Dose – IV: load 15 mg/kg over 1 hour, then 30-80 g/kg/min – (level 5-10 ng/ml) – PO: 30-70 mg/kg/day • Side effects: Lupus- in slow acetylators – ANA + : 50-90% Symptoms: 20-30 %
Arrhythmia-focused Therapy Procainamide has been a long-used intravenous infusion for a wide range of dysrhythmias Narrow complex tachycardia Atrial tachycardia, resistant re-entrant tachycardia Wide-complex tachycardia Ventricular tachycardia Downside: Side effects, negative inotrope, pro arrhythmic
Arrhythmia-focused Therapy • Procainamide has been a long-used intravenous • infusion for a wide range of dysrhythmias: – Narrow complex tachycardia: • Atrial tachycardia, resistant re-entrant tachycardia – Wide-complex tachycardia: • Ventricular tachycardia • Downside: • Side effects, negative inotrope, proarrhythmic