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Title: HIGH RESOLUTION ECG/ SIGNAL AVERAGED ECG
Description: Notes on indications for procedure, measurements needed for positive test, lead positions and lead system used. Explanation of late potentials and slow propagation

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HIGH  RESOLUTION  ECG  (SIGNAL  AVERAGED  ECG)  
 
It  is  used  to  identify  slow  propagation  of  myocardial  conduction  that  is  not  evident  on  a  
surface  ECG
...
 
 
Conduction  abnormalities  are  shown  as  “late  potentials”  on  the  signal  averaged  ECG
...
   
 
PROPERTIES  OF  POTENTIALS:  
• LATE:  they  occur  at  the  latter  part  of  depolarisation  (therefore  occur  at  the  terminal  
portion  of  the  QRS  complex)
...
 
• LOW  AMPLITUDE:  abnormal  propagation  through  areas  of  slow  conduction  means  
low  amplitude  signals  occur  due  to  the  small  amount  of  tissue  being  propagated
...
   
On  a  surface  ECG  it  can  look  like  right  bundle  branch  block  (RBBB)  with  J  point  elevation/  ST  
elevation  typically  occurring  in  leads  V1-­‐V3
...
 This  is  the  
addition  of  every  extra  cellular  action  potential  that  leads  to  ventricular  depolarisation
...
 These  are  clinically  significant  
as  they  represent  slow  conduction
...
 Ideally  
the  noise  is  reduced  to  0
...
 This  enhances  the  detection  of  low  amplitude  signals  by  
amplifying  the  terminal  portion  of  the  QRS  complex
...
   
Subdued  lighting    
The  electode  sight  must  be  clean  to  reduce  baseline  wander
...
   
 
X  Lead  =  HOROZONTAL  PLANE  (V6  –  V6R  also  known  as  I)  
Y  Lead  =  VERTICAL  PLANE  (E-­‐  H)  
Z  Lead  =  SAGITAL  PLANE  (Left  leg  –  M)    
All  limb  leads  are  required,  and  apply  V4  and  V6
...
   
 
I  –  right  midauxillary  line,  same  plane  as  V4  and  V6  
E-­‐  Anterior,  mid  sternum  on  the  same  horizontal  level  as  V4  and  V6  
H-­‐  Centre  of  the  back  of  the  neck    
M-­‐  Posterior,  centre  of  the  back  “opposite”  E  
 
MEASUREMENTS:  
Root  mean  squared  (RMS)  voltage  of  final  40ms  of  QRS  
Duration  of  low  amplitude  signals  (LAS)  lass  that  40um  
Duration  of  entire  signal  of  complex  
 
POSITIVE  TEST:  
Must  meet  at  least  2  of  the  3  criteria    
1
...
LAS  less  than  38ms    
3
...
 
 
 


Title: HIGH RESOLUTION ECG/ SIGNAL AVERAGED ECG
Description: Notes on indications for procedure, measurements needed for positive test, lead positions and lead system used. Explanation of late potentials and slow propagation