Tachycardia refers to a high resting heart rate.
In general, a resting adult heart beats between 60 and 100 times per minute. When an individual has tachycardia, the upper or lower chambers of the heart beat significantly faster.
When the heart beats too rapidly, it pumps less efficiently and blood flow to the rest of the body, including the heart itself, is reduced.
Because the heart is beating quicker, the muscles of the heart, or myocardium, need more oxygen. If this persists, oxygen-starved myocardial cells can die, leading to a heart attack.