Hi Jill, This time last year, after 3 lots of Herceptin along with 2 other chemo drugs I to had to have a break becasue my heart did the same as yours. I ended up in isolation ward for 5 days becasue my blood count dropped also. I had to stay off herceptin until I finished my radiotherapy, I missed 3 lots and then started again with another big dose. My heart count along with everything else came back to normal and I have now finished all my treatment. I stayed really positive through the whole thing but asked lots of questions and felt satisfied with the answers given. Request tests if you want them, it is your body and you should be able to find out what ever you can.All the very best wishes for a complete recovery from this unreal journey we have all travelled.