<prompt> It is essential to give b blocker or Digoxin to increase the refractoriness of AV node AVN prior to administration of ___ for treatment of atrial fibrillation.QuinidineFlecainideMoricizineAll of the above  <response>: Ans. d All of the above Ref: Harrisons Internal medicine 16th pg. 1345.Class la and Ic drugs have vagolytic property and can convert AF to flutter and increase paradoxically ventricular rate and hence to prevent this drug i.e., beta blockers should be added prior to this drug to increase refractoriness of AV node.Class IAQuilidine, Procainamide, Disopyramide.The Queen Proclaims Disos pyramid.Mechanism Ap duration, effective refractory period ERP, QT interval.Clinical useBoth atrial and ventricular arrhythmias, especially re-entrant and ectopic SVT and VTToxicityCinchonism headache, tinnitus with quinidine, reversibleSLE-like syndrome procainamide, heart failure disopyramide, thrombocytopenia, torsades de pointes due to QT interval.Class IBLidocaine, Mexiletine.Mechanism Ap duration. Preferentially affect ischemic or depolarized Purkinje and ventricular tissue. Phenytoin can also fall into the IB category.Clinical useAcute ventricular arrhythmias especially post-MI, digitalis- induced arrhythmias. IB is Best post-MI.ToxicityCNS stimulationdepression, cardiovascular depression.Class ICFlecainide, Propafenone. Can 1 have Fries, Please.MechanismSignificantly prolongs refractory period in AV node.Minimal effect on AP duration.Clinical useSVTs, including atrial fibrilation. Only as a last resort in refractory VT.ToxicityProarrhythmic, especially post-MI contraindicated. IC is contraindicated in structural and ischemic heart disease. 