It is a normal response to increased demands on the heart, such as exercise or other stress. It may accompany infections and fevers. It may also be associated with conditions such as high thyroid or dehydration. Patients with heart failure or other heart conditions may have an increased rate to make up for a lower amount of blood ejected with each beat. Poor physical conditioning can lead to increased resting heart rates, an particularly to a rapid increase in the heart rate when engaging in physical activities.
Chocolate contains significant amounts of stimulants.
Nicotine and other stimulants and toxins in cigarettes, cigars, snuff and other tobacco products. Some prescription medications. These impulses occur prematurely, before the sinus node depolarizes. They are conducted through the atrium and slow down, just like a normal sinus beat, when they reach the A-V node. They are conducted through the ventricle in the same fashion as a normal sinus beat.