use dependance describes the state in which class 1 antiarrhythmic actually works, as y increase the heart rate ..... more fast Na channels are available in active and in inactive form...thereby more available binding sites for class 1 ... in case of 1c it has strong use dependance as this group has very slow dissociation from the Na channel when it turns into resting state ...thus in the next AP y will find not only active and inactive channels are blocked by this drug but y will find also Na chan in resting states blocked ....which decreases the n of Na ch available for Upstroke of AP ....increasing the threshold and decrease the slope of phase 0 ...prolonging the APD , qrs complex and ERP ....and this effect in class 1 is cumulative becs in every AP y increase the n of resting Na chan which are blocked so we say in this case we have strong use dependance for class 1c ....... use dependance =heart rate dependance ...as y increase the HR ...y increase the action of antiarrhytmics
Posted on: Wed, 19 Mar 2014 21:08:11 +0000
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