RT Book, Section
A1 Anderson, Robert H.
A1 Sizarov, Aleksander
A1 Moorman, Antoon F. M.
A2 Pahlm, Olle
A2 Wagner, Galen S.
SR Print(0)
ID 8763644
T1 Chapter 17. Development of the Heart, with Particular Reference to the Cardiac Conduction Tissues
T2 Multimodal Cardiovascular Imaging: Principles and Clinical Applications
YR 2011
FD 2011
PB The McGraw-Hill Companies
PP New York, NY
SN 978-0-07-161346-0
LK accessmedicine.mhmedical.com/content.aspx?aid=8763644
RD 2024/04/23
AB It  is,  perhaps,  unfortunate  that  the  myocytes  that  generate  and  dissipate  the  cardiac  impulse  throughout  the  myocardial  body  are  known  as  the  cardiac  conduction  tissues,  because  all  myocytes  within  the  heart  possess  the  capacity  to  conduct.  The  alternative  title,  the  "specialized  tissues,"  is  equally  unfortunate,  because  from  a  developmental  stance,  as  we  will  show,  the  so-called  conducting  tissues,  in  particular  the  nodal  components,  share  important  features  with  the  myocytes  of  the  primary  heart  tube.  It  is  their  so-called  "working"  partners  that  show  more  evidence  of  developmental  specialization.  In  this  chapter,  therefore,  we  will  describe  the  processes  whereby  the  initial  heart  tube  grows  by  addition  of  myocardium  at  both  its  venous  and  arterial  pole,  how  it  loops,  and  how  eventually  it  becomes  converted  into  the  four-chambered  organ.  In  this  definitive  structure,  it  is  the  sinus  node  that  generates  the  cardiac  impulse,  this  being  propagated  within  the  atrial  musculature,  delayed  in  the  atrioventricular  node,  and  then  conducted  rapidly  to  the  ventricular  myocardium  through  the  atrioventricular  bundle,  its  branches,  and  the  ventricular  ramifications  known  as  Purkinje  fibers.  We  will  also  discuss  the  fate  of  the  more  widespread  areas  of  primary  myocardium  found  in  the  developing  heart  because  it  is  almost  certainly  the  remnants  of  these  areas  in  the  postnatal  heart  that  are  the  substrates  for  many  cardiac  arrhythmias.  In  contrast,  with  regard  to  perhaps  the  most  important  arrhythmia  in  the  ageing  population,  namely  atrial  fibrillation,  we  will  show  how  the  pulmonary  myocardial  sleeves,  known  now  to  be  the  substrate  for  many  forms  of  atrial  fibrillation,  are  derived  from  so-called  working  rather  than  specialized  conducting  tissues.