RT Book, Section
A1 Zimmerman, Franklin H.
SR Print(0)
ID 1200100195
T1 Accessory Pathways and Preexcitation
T2 ECG Core Curriculum
YR 2023
FD 2023
PB McGraw Hill Education
PP New York, NY
SN 9780071785211
LK accesscardiology.mhmedical.com/content.aspx?aid=1200100195
RD 2024/04/24
AB In  the  normal  heart  a  dense  band  of  fibrous  tissue  forms  early  in  embryogenesis  to  anatomically  and  electrically  insulate  the  atria  from  the  ventricles.  The  only  natural  electrical  link  between  the  atria  and  the  ventricles  is  via  the  AV  node  and  His-Purkinje  system.  Ventricular  preexcitation  is  said  to  occur  when  all  or  part  of  the  ventricular  myocardium  is  activated  by  the  atrial  impulse  earlier  than  would  be  expected  if  the  stimulus  were  to  reach  the  ventricles  by  way  of  the  normal  AV  conduction  system.  This  premature  activation  can  occur  only  if  there  is  an  alternate  route  that  allows  the  electrical  stimulus  to  bypass  the  normal  physiologic  delay  of  the  AV  node.  Atrioventricular  bypass  pathways  are  embryologic  remnants  of  muscle  bundles  that  bridge  the  heart’s  fibrous  skeleton,  providing  the  means  for  abnormal  electrical  conduction  between  the  atrium  and  ventricle  (Figure  9-1).  Transmission  of  the  electrical  impulse  over  such  an  accessory  pathway  produces  characteristic  findings  on  the  ECG  and  may  provide  a  substrate  for  cardiac  arrhythmias.