Reentry

• normally, conduction activates heart in sequence. the wave of depolarization is extinguished, requiring subsequent SA node discharge to depolarize the myocardium for the next beat

• in reentry, a group of cells is not activated by SA node but is rather activated in a retrograde fashion, serving as a bridge to reactivate areas that have now recovered

• three requirements for reentry—this is very important

  • 1 dispersion of repolarization: tissues repolarize again at varying rates

  • 2 unidirectional conduction block

  • 3 slow conduction: even without specialized conduction tissue, heart tissue normally transmits potentials so fast that reentry would not occur even if the other two criteria were present

Category: Cardiology Notes