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Posts Tagged ‘verapamil for vt’

Read with caution . This  may either injure or cure your patient !

Click on the ECG to view what happend !

 

How does  verapamil  terminate a  VT  ?

Physicians  often  debate  vigorously before   labeling  a cardiac arrhythmia as ventricular , atrial junctional  , abberant or not etc etc .  But  for  an arrhythmia   it matters little  from what  chamber it is going to to originate . After all ,  any cell in the heart if excited can generate an arrhythmia .  The ion channel abnormality and the influx and efflux of ions  that determines how a drug is going to terminate an arrhythmia.

In fact , way back  in 1989 the Sicilian Gambit stressed this concept when classifying anti-arrhythmic drugs .This classification taught us  , even though there is a  huge list of  clinical cardiac arrhythmias  , from the therapeutic point of view there are only a handful of receptors  (scattered  all around ) to target  !

When we look at this angle , we realise  , many of  ventricular action potentials  have  important slow  calcium currents  similarly  junctional action  potentials do have some  sodium currents.  Calcium current  is present in every  myocardial cell  more so in the vicinity of AV junction.  Further , at times of ischemic or hemodyanmic stress these ion channels  may  take a different avatar altogether.Slow sodium channels and fast calcium channels etc !  (A wild imagination or is it a fact ?) Other important targets are potassium channels

Heart is a complex structure both macro and microscopically  .  In the three dimensional  histopathologic   interface between atrium  and ventricle (Especially in the  basal areas , outflow tracts  , around the AV grooves ) there  are  lot of sharing  and overlap of  different morphology  of cells . A high septal VT can behave  exactly like an SVT  which  includes the  tendency to get terminated by calcium channel blockers.

Amiodarone is a most popular  drug for VT termination ? Are we clear about the mechanism of it’s  action in terminating VT ?

It is  more of a perception and belief  that  class 3 action   may be   responsible for termination of VT by Amiodarone . In reality it is very difficult   to prove this point.  As Amiodarone  has all the  4 classes  action that includes beta and calcium blocking properties.. In fact ,  now  there is evidence  to  suggest   beta or calcium blocking action  may be more important in terminating  VT when  it is administered  IV  . (While  the class 3 action predominates in long term oral therapy )

A verapamil sensitive   VT may  successfully  be terminated by  Amiodarone  not by its  unique  action  instead it   may simply represent  its  calcium blocking  property.

Final message

Many  of the  VTs terminated by Amiodarone   could  also be verapamil sensitive . Since verapamil is never tried first we will never ever know the incidence of such phenomenon that gives pseudo credit  to Amiodarone

It may not be big crime to try injection verapamil in some of  the  stable ventricular tachycardias( As my fellow did ) especially  when we we know there is an entity called verapamil sensitive VT !


Q for the readers :

How many deaths are reported in cardiology  literature  regarding    fatality  following   verapamil  in   VT ?

I am trying to find  the answer the  data is very hard to come by !

Critical comments welcome.

 

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