• Afterdepolarizations are new action potential (AP) triggered during--
Phase 2-3 of the previous action potential (early afterdepolarizations or EADs)
Beginning of phase 4 of the previous action potential (delayed afterdepolarizations or DADs)
• Afterdepolarizations are major causes of various types of ventricular tachycardia including polymorphic ventricular tachycardia (e.g Torsades de pointes, bidirectional VT), and ventricular fibrillation.
• A normal action potential of the myocyte has 4 phases (illustrated below):
(0) rapid upstroke
(1) early repolarization
(2) plateau
(3) repolarization
(4) resting membrane potential
