"Arrhythmia" refers to any change from the normal sequence of electrical impulses. When the heart doesn't beat properly, it can't pump blood effectively.
Pacemakers assist the heart when your heart slows. The pacemaker will stimulate her heart to increasr the heart rate.
The Automatic Implantable Cardiac Defibrillator (AICD) protects the heart against life-threathening arrhythmias.