Hyperthyroidism and heart failure

My docotor said if this hyperthyroidism is left untreated in cause to heart failure. I have had symptoms for 3 months and they just figured it out 2 weeks ago that I have hyperthyroidism. MyTSH is less than .1. Normal is above .4. How long ahs anyone had hyperthyroidism? and how ong did it go untreated? I am going to see a endocronologist tomorrow so I will keep you posted. I would really appreciate any input anyone has. I am a mother of 2, a 3 year old and a 3 month old and I am a NERVOUS wreck,.