Hello..
Well yes fluctuating
thyroid levels does have an impact on heart..first thing is I want to kno whether he has been diagnosed with hypo or hyperthyroidism.. Secondly what are the
tsh,t3,t4 levels .third thing what are the current medications? Best thing I can suggest you is to consult a physician and please follow up with the thyroid profile test once in 3 months as it will help us to assess your thyroid levels correctly and alter the dosage too