<prompt> All of the following statements are true about quinidine except:It blocks myocardial Na channels primarily in the open stateIt has no effect on myocardial K channelsIt produces frequency dependent blockade of myocardial Na channelsIt delays recovery of myocardial Na channels  <response>: Ref: KDT 6e p511, 512 Quinidine is a class I antiarrhythmic agent. It blocks Na channels in the open state and also delays the recovery of these channels. Blockade by these antiarrhythmic agents is frequency dependent. Class Ia antiarrhythmics, in addition blocks myocardial K channels also. 