<prompt> Quinidine exes its action on the hea byCa2 channel blockadeNa channel blockadeK channel openingCl- channel opening  <response>: It is d-isomer quinidine is used as an antiarrhythmic drug. Quinidine blocks myocardial Na channels. Class 1a group of drugs- quinidine, procainamide, disopyramide Ib: Lidocaine, phenytoin Ic-encainide, flecainide Ref: KD tripathi 8th ed. 