A cardioverter defibrillator can be surgically implanted in a patient’s chest or abdominal region as a means of controlling heart arrhythmias that may lead to cardiac arrest. The difference between an implantable cardioverter defibrillator (ICD) and a pacemaker is that while a pacemaker can emit low-energy electrical impulses to restore a normal heartbeat, an ICD can go one step further and provide higher-energy pulses (shocks) for defibrillation when and if a normal rhythm can’t be restored by the lower-intensity pulses. Moreover, some implantable defibrillators (called CRT devices) can provide cardiac resynchronization for patients with heart failure in order to ensure that both ventricles are paced to work together. ICDs are larger than pacemakers and specifically designed to prevent someone from dying of cardiac arrest, whereas pacemakers are designed to simply speed up or slow down an irregular heartbeat when needed. Surgical placement of a defibrillator is also somewhat more complicated than what is required for a pacemaker implantation. One reason is that it is necessary to test the defibrillator device by actually causing the patient to go into cardiac arrest. This requires the patient to be strongly sedated but can be done with a reasonably high degree of safety.