EADs and DADs

• EAD is shown in A, B, C. action potential is prolonged; membrane fluctuations result in an extra, ectopic beat. this can lead to ventricular tachycardia, which can be dangerous

• DAD is shown in D, E. depolarization occurs after the membrane has repolarized, but this still may cause ventricular tachycardia

EADs

• occur before the full repolarization o the cell

• congenital

  • familial long QT syndrome (LQTS): genetic mutations in K+ or Na+ channels prolong action potentials; this leads to EAD

  • high risk for sudden death due to torsades de pointes (vtach)

  • treat with β-blockers and implantable cardioverter-defibrillators (ICDs)

• acquired

  • acquired long QT

  • most often due to drugs (e.g. terfenadine); also, ischemia, hypocalcemia, hypothermia

  • these patients are also at risk for VT

  • treat by remove offending cause and correct any electrolyte abnormalities

DAD

• occur after cell repolarizes

• example: digitalis toxicity

  • treatment involves correction of electrolytes, IV Mg, defibrillation

Category: Cardiology Notes