RT Book, Section
A1 Prystowsky, Eric N.
A2 Prystowsky, Eric N.
A2 Klein, George J.
A2 Daubert, James P.
SR Print(0)
ID 1176522068
T1 Apparent Paradoxical Conduction
T2 Cardiac Arrhythmias: Interpretation, Diagnosis, and Treatment, 2e
YR 2020
FD 2020
PB McGraw Hill
PP New York, NY
SN 9781260118209
LK accesscardiology.mhmedical.com/content.aspx?aid=1176522068
RD 2023/03/21
AB Conduction  of  premature  atrial  complexes  (PACs)  is  usually  predictable  in  a  patient  with  a  relatively  constant  heart  rate.  A  late  (i.e.,  long  atrial  coupling  interval)  PAC  will  conduct  to  the  ventricle  and  a  relatively  early  (i.e.,  short  atrial  coupling  interval)  PAC  often  blocks  in  the  atrioventricular  (AV)  conduction  system.  In  some  instances,  however,  apparent  paradoxical  conduction  can  occur  in  the  AV  conduction  system.  This  happens  when  a  late  PAC  conducts  to  the  ventricle,  an  earlier  PAC  blocks,  but—unexpectedly—a  PAC  with  even  a  shorter  coupling  interval  again  conducts  to  the  ventricle.  Various  electrophysiologic  phenomena  can  explain  these  conduction  patterns,  but  they  are  often  very  difficult  to  diagnose  by  surface  electrocardiography  only.  Resumption  of  conduction  may  occur  because  of  supernormal  excitability  and  conduction,  which  is  probably  relatively  rare,  but  more  commonly  can  be  explained  by  other  mechanisms,  especially  the  gap  phenomenon.  Specific  issues  related  to  the  bundle  branch  conduction  system  are  presented  in  detail  in  Chapter  3.