A. Electrophysiological basis of arrhythmias D 1. Normal cardiac electrophysiology I Excitability: ability to produce action potentials maximal diastolic potentials(MDP) thresold levels D Automaticity: pacemaker phase 4 slope D Conductivity conduction pathways, phase 0 amplitudeA. Electrophysiological basis of arrhythmias 1. Normal cardiac electrophysiology Excitability: ability to produce action potentials maximal diastolic potentials (MDP) thresold levels Automaticity: pacemaker phase 4 slope Conductivity: conduction pathways, phase 0 amplitude