Tachycardia isn t really fatal. All that means is that your heart has an extra or irregular beat every so often. I have tachycardia and I m healthier than 2 oxen. I look younger than I am and am in really good physical health. Basically there is a group of cells that controls your heart rhythm and this group of cells, every once in a while, causes a funny beat - that s it. Other than that your heart is healthy (unless there is some other problem). My doctor told me that I may have lived my entire life without even knowing I had tachycardia except that I got electrocuted badly enough to go into arrhythmia. I hope this helps.