Your heart rate is fine while working out. Your max predicted heart rate is calculated as 220 - your age which is 204 for you so no worries. As far as a heart attack from a blood clot, it is very rare and even more so at your age, don't worry about things like heart attacks, enjoy life.
200 bpm is high but a healthy heart in a young man should handle that just fine, as Jon told you.
That said, you don't need to stay at 200 bpm to get effect from your exercise. Most people are not able to sustain that heavy exercise for a long time, maybe just a few minutes. I would say it's better to stay at a lower percentage of max (in your case, without knowing your resting heart rate, maybe 160-180 bpm) for half an hour or more. That would probably give better results :)
But all exercise is great! Just keep in mind that when you work out at max intensity, warm-up is essential.
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