Tachycardia is an abnormal condition in which the
heart (myocardium) contracts regularly but at a
rate greater than 100 beats per minute. The heart
rate normally speeds up in response to fever, exercise,
or nervous excitement.
Pathological tachycardia goes along with lack of
oxygen (anoxia), as caused by anemia, congestive
heart failure, bleeding, or shock. A slow heart
beat (bradycardia) develops because the heart muscle
gets too-little oxygen and cannot maintain the sped-up
pace.
