Final answer:
AICDs detect arrhythmias such as cardiac or ventricular fibrillation and tachycardia using an electrocardiogram, and when these are detected, they deliver antitachycardia therapy which includes pacing or a defibrillation shock.
Step-by-step explanation:
AICDs, or Automated Implantable Cardioverter-Defibrillators, are medical devices that are programmed to detect certain types of arrhythmias, such as cardiac or ventricular fibrillation and tachycardia. These arrhythmias are characterized by an abnormally fast heart rate or irregular heart rhythms that can be life-threatening. When such arrhythmias are detected, the AICD administers antitachycardia therapy, which may include delivering a series of rapid pacing stimuli or a defibrillation shock to restore the heart's normal rhythm. AICDs continuously monitor the heart's electrical activity through an electrocardiogram (ECG), and when the device detects arrhythmic events that fall outside of pre-programmed parameters, it responds with the appropriate time-sensitive therapy.