Group IA drugs slow phase 0 depolarization prolong action potent and slow conduction. n(1)Class I 0 0 (Nat channel blockers) d Class Ia (moderate Nat K channel blockers) Dlastolic currents Action potential u moderately block Nat channels, conduction APD and erp个 Ca quinidine奎尼丁 procainamide普鲁卡因胺 Quinidine,procainamide and disopyramide block open or inactivated sodium channels. These drugs have an intermediate rate of association with sodium channels.(1) Class I (Na+ channel blockers) Class IA (moderate Na+ channel blockers)： moderately block Na+ channels, conduction , APD and ERP  quinidine 奎尼丁 procainamide 普鲁卡因胺