A. Electrophysiological basis of arrhythmias o 1. Normal cardiac electrophysiology u Excita bility: ability to produce action potentials maximal diastolic potentialS(MDP) threshold levels u Automaticity: pacemaker phase 4 slope u Conductivity: ability to conduct impulse conduction pathways, 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: ability to conduct impulse conduction pathways, phase 0 amplitude