PHARMACY Lecture Notes - Lecture 1: Atrioventricular Node, Qt Interval, Propafenone
Document Summary
States of na+ channels: open during upstroke (p0) Na & ca blockers alter threshold potential (tp) aka the cfl. K blockers (class iii function) prolongation of repolarization (p3) prolong (apd) action potential duration prolonged erp. Sa node: automaticity by tp (hard to create an action potential) & slope of p4 or slow. Ventricular myocyte: slow down or reduce slope of or upstroke (p0) this is the main na+ channel blockade function. Ic strong some prolongs repolarization (p3) ---- additional potassium channel blockade apd increases erp. Class ia ( paq, die ) moderate na+ blockade + erp anti-cholinergic/anti-muscarinic/atropin-like effects : d > q > p. Threshold for excitation in atrium and ventricles direct depressant action. More cardiac anti- muscarinic effects than procainamide. Similar to procainamide least appropriate/ most dangerous class i drug. Greater cardiac anti- muscarinic effect than quinidine (drug that slows av conduction is given with it) conduction. Precipitation of new arrhythmias such as torsades de pointes (tdp)
