But you're lucky, relatively speaking. If you were shot in the heart, your blood pressure would quickly drop, but it would take 10 to 15 seconds to lose brain function. In that time you could draw your gun, utter last words, or spend some time thinking about your unfortunate situation.
Caffeine can cause indigestion, which in turn may lead to heart palpitations. However, arrhythmia (abnormal heart rhythm) can also cause palpitations, and this condition is more of a concern. Seek medical attention if your palpitations last longer than two or three minutes.
Whether heart palpitations are serious or not depends on your overall health. If they are caused merely by indigestion, you probably don't have much to worry about, but truly understanding the cause of your palpitations or irregular heartbeat is critical.