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Archive for April 23rd, 2012

What does Amiodarone do to the ventricular rate in AF ?

Posted in cardiac drugs, Cardiology - Clinical, Cardiology - Electrophysiology -Pacemaker, cardiology -Therapeutics, Cardiology-Arrhythmias, Clinical cardiology, tagged , , , , on April 23, 2012| 2 Comments »

Amiodarone acts  by

  1. Correcting the  rhythm  to sinus .
  2. Controls  ventricular rate  alone
  3. Does both ?

Answer is 3

How can it correct the rhythm alone ?  If  the rhythm is corrected ,  rate will automatically be controlled,  unless Amiodarone converts AF into Sinus tachycardia  which is very unlikely !

Of course  Amidarone  is not a  magic drug .The success rate of  Amiodarone  restoring  sinus rhythm is far . . . far less . . . than our expectations ! . It fails to  convert to sinus rhythm in a significant chunk *. Interestingly ,   it may still  control the  ventricular response  by its beta blocking action .

*Our estimate is , the failure rate Amiodarone  is  between  30-40%  or even higher ,  as   bulk of AF we witness   is due to Rheumatic heart disease.

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Which is the best drug for ventricular rate control in atrial fibrillation ?

Posted in Uncategorized, tagged , , on April 23, 2012| 1 Comment »

Which is the best drug  for  “ventricular rate  control” in atrial fibrillation  ?

  1. Digoxin alone
  2. Diltiazem alone
  3. Atenolol alone
  4. Digoxin +Atenolol
  5. Digoxin + Diltiazem

The answer is 4.

This is based on a study  done by Bramh N  Singh  and his team  from California published in 1999 . (http://content.onlinejacc.org/cgi/reprint/33/2/304.pdf  )It  was  a wonderful study   involving  just  12 patients ,  still good enough to prove a  point . It was a sequential cross over study a rare theme in medical trials !  where same patients act as control .Hence bias and host variations are  nil. Few excerpts from the study .

It is very clear, for optimal rate control we need a combination regimen , Digoxin must be one of them .Atenolol combined well with Digoxin , even as though Diltiazem resulted in maximum dip in nocturnal heart rate.

Digoxin + Atenolol is clear winner in rate control during exertion as well ! Note Digoxin has absoutely no control over the heart rate at times of exercise !

Few thoughts about this study

This study has clearly documented superiority of combined drug regimen for rate control in AF .

Still it leaves a  lingering question !  Why verapamil was not used as an agent in this study  ?

If only ,  verapamil was used (As we do in our hospital )   Digoxin -Atenolol  combination would have  faced a  really  tough competiton.

Another  curiosity is  ,  what would  have  been the power of a unique combination   of Atenolol  and Diltiazem  in controlling  ventricular  rate in AF ?

Any way , it was a wonderful cross over study  . Such studies are a rare breed ,  always welcome in this world  of  funny  pharma trials  wherein  a new drug is  compared with a dud drug called placebo !

Now  . . . Try this  one

Amiodarone

  1. Corrects  rhythm
  2. Controls  ventricular rate
  3. Does both ?

How can it correct the rhythm alone ? If rhythm is corrected ,  rate will automatically be controlled unless Amiodarone converts AF into Sinus tachyardia !

Of course  Amidarone  fais to  convert to sinus rhthm in many , still it may control the rate  by its beta blocking action.

Reference

http://content.onlinejacc.org/cgi/reprint/33/2/304.pdf

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