Question: why does my heart rate increase all of a sudden?
Answer: Tachycardia Tachycardia occurs when your heart suddenly starts beating very fast. If it happens as a result of exercise, excitement, or fever, it's usually not a cause for concern and doesn't need treatment. But one type of arrhythmia called paroxysmal supraventricular tachycardia (PSVT) is more dangerous.