Brief Answer:
If properly monitored it would be very effective for long years to come .

Detailed Answer:
Hello ,
I am Dr. Mody and no I would be addressing your concern .
Tykosin contains Dofetilide and it's mostly used around the world for atrial fibrillation ( ? defib as you mentioned ) .
Generally if closely monitored , it is very effective and the effectiveness is long lived .
one has to understand that the aim of giving tykosin is not to completely stop the episodes of atrial fibrillation, but to decrease the interval between two episodes and if an episode occurs to decrease the severity of the episode .

Hence do follow up closely with your cardiologist so he can monitor certain parameters and make necessary changes in the dosage of tykosin when necessary and you should do good . Also take other medications along with tykosin .

Let me know if any clarification is needed .
Also you may upload your medical records so I can guide you better.

Regards Dr. Mody

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