Aug 17, 2015
“Use Dependence” Phenomenon
Refers to enhanced pharmacologic effects during faster HRs, seen in class I and iV anti arrhythmic agents
Progressive decrease in impulse conduction + widening of QRS complex d/t increased #of blocked channels in patients w/faster HRs (drug has less time to dissociate from Na+ channels) Most freq seen w/ class IC anti arrhythmic agents (i.e. flecainide, propafenone; slowest rate of drug binding dissociation) Use: a fib , supra ventricular arrhythmias ---------------------------------------------------------------------------------------- Extras: Digoxin - slow conduction through AV node CCB - prolongation of refractory period of AV node --> increased PR interval