Red Bull drinks are okay in moderation but when you drink too much of the Red Bull then it can cause health problems including heart problems.
The Red Bull drinks do increase your heart rate so if you have heart problems it's best to avoid drinking any Red Bulls just to be safe.
One large can of Red Bull contains 80 mg of caffeine so you can easily overdose on caffeine if you drink too many.
Drinking 2 Red Bulls in a day is usually the safest limit but you should drink no more than 5 Red Bulls in one day otherwise you can overdose on the caffeine and possibly have an increased heart rate that can get too bad and cause a heart attack.