Not qualified to make a for certain answer re: defibillator and CS, but my gut feeling is that CS on the wrist would not affect the electrics of something in the chest.
Especially with this product.http://tinyurl.com/hfm2zu7 which is CS in a gel form. You can just put a dab on a individual sore, or spread it completely over the rash. Then wrap it with a gauze bandage to keep it from getting on clothes, or bedding. This will keep it in contact longer. It is advised with all CS products that you re-apply until it does it's job.
I use this product and can tell you it works, but the decision is yours.