I'm not sure if an elevated HR can "cause" a stroke or heart attack, but I think it's something you should talk with your doctor about. Is your resting HR always above 100? Your doctor may have some suggestions or thoughts on how to manage an elevated HR.
I too have a high heart rate, called supraventricular tachycardia. I'm a nursing student and I've had it for a few years. Sometimes it will get up to 200+ bpm and I get dizzy or faint. The first time it happened I was 17 and was taken in an ambulence from school, they gave me nitroglycerin even. It was scary but by the time I got to the hospital it had gone down to around 100-120, my normal. I was told to relax and rest. It never went away and recently I was at my clinical in the hospital and it happened again and finally I was taken seriously. I fainted and was immediately taken down to ER where a ton of people were hooking me up to all kinds of things they told me they thought I was having a heart attack. Forturnatly I went back down and I saw another cardiologist who told me it has to do with the electrical firing of the heart. for some reason our hearts misfire and this causes a fast heart rate and can cause chest pain. There putting me on meds and I may have to have surgery but I wouldnt worry about that because he said that its rare. In fact most of the time no treatment is neccessary. However it is important to get an appt. w/ a cardiologist, b/c its not good for your heart to work that hard all the time. -Good luck!
By the way when your heart beats that fast your not getting as much Oxygen to your brain and this causes irritability, restlessness, fatigue and increased respiration. This shouldnt cause stroke because thats when blood is cut off to the brain, usually from a clot. A heart attack is also extremely rare, and I definitely wouldn't worry about that. When it happens just lay down and try to relax, also coughing, baring down, and holding your breath for a few seconds can cause your heart rate to decrease. Hope that helps. :)
There are many causes of tachycardia, from atrial fibrillation to supraventricular tachycardia, so we cannot jump to any conclusions. You should see a cardiologist to get a full workup, including but not limited to labs and EKG.