Excitability: [KlECF I-K permeability I- depolarization repolarization excitability ECGT wave↓ Conductivity: RP|-0 phase ofAP↓ conductivity I conductive block unidirectional block ECG P-R tExcitability: [K+ ]ECF K+ permeability depolarization repolarization excitability ECG T wave Conductivity: RP 0 phase of AP conductivity conductive block unidirectional block ECG P-R