Energy drinks with herbal or chemical ingredients along with a high content of caffeine can have different effects on the electrical functioning of your heart than plain caffeinated beverages do. A study on energy drinks involving healthy military personnel measuring blood pressure and doing ECGs showed changes in heart function starting 2 hours after consumption.
The electrical time it takes to for the lower chambers of the heart to recharge after each beat in order to beat again is called the “QT interval”. The study originally published in medical journal*, showed a delay of 10 milliseconds occurring in personnel who consumed energy drinks. (The FDA labels drugs causing a 6msec QT interval delay with a warning.) The effects were short term, but are they cumulative?
Please do not assume herbal/natural preparations are automatically safe. Our bodies are unique; therefore what is good or safe for someone may not be for you.