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