PS I forgot to mention my own experience with palpitations; they have more or less disappeared after 1 1/2 years on iodine. The Salt loading / a la watercure also helped a lot.
I now start and end my day with a large glass of salty water.
The palpitations was a big concern for me; as my father has severe arrhythmia and my mother has it + a slow heart rate, low blood pressure +++
None of them take iodine, but my mother did improve when I finally convinced her to use more real salt; she believed for some years that this was bad for her kidneys. The opposite happened; kidneys and some other symptoms improved. Next is iodine; but she is a hard nut to crack here.
BTW ; consider the suggestion from Newport ; Hawthorne is a great heart remedy, and almost forgotten these days.