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At 14 yrs of age there is hardly any chance to get a heart disease
if you do not have any problem since birth.Anxiety
by it self may mimic any disease because a human mind can imagine anything so you may even imagine a heart attack
For a young person like you at your age there is hardly any reason for anxiety just relax get treated and try to concentrate on studies and keep yourself occupied so that your mind does not wander and it will help you reduce anxiety.