Greetings NJHemily! Welcome to the healthboards.
The thyroid needs the right amount of iodine too much may speed up the heart. Of course some is in salt. Too low can cause health problems also. An endocrinologist might be someone to see for this.
The heart can also have problems if there is too little or too much water in the body. The vast majority of people probably forget to drink the proper amount of water and are a bit dehydrated at times. Some beverages such as coffee, chocolate, alcohol, sweet drinks or things with artificial ingredients may also cause difficulties. Of course everyone is responsible for their own health care decisions.