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.
Correct Answer: All of the above
Description: Ans. d (All of the above) (Ref: Harrison's 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 Diso's 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 stimulation/depression, 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.
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