Selenium; "Wallach also lists other effects of selenium deficiency: anemia (red blood cell fragility), fatigue, muscular weakness, myalgia (muscle pain), muscular dystrophy (white muscle disease in animals), cardiomyopathy (sudden death in athletes), heart palpitations, irregular heartbeat," http://www.greenwillowtree.com/Page.bok?file=selenium.iodine.html
Magnesium (in the right form, as malate or citrate)
Heart beat problems/palpatations is one of the many symptoms of hypo T.
For the dosage of Iodoral; pleace search within this forum as there are many roads to Rome, some go slow, others jump into it.
Within a year of Iodine supplementation + all companions,my palpitations stopped; and if it happens it is usually due to a supplement I took or something I ate (as Mono-Sodium-Glutamat (Natrium Glutamat) or heavy vit B)