An Automatic Implantable Cardioverter Defibrillator (AICD) is a permanent electronic device that is implanted into a person’s chest to monitor an abnormally beating heart, either one that beats too slow (Bradycardia), too fast (Tachycardia) or irregularly (Atrial Fibrillation). All of these abnormal heartbeats are referred to as arrhythmias. These devices are mainly used for the treatment of life-threatening arrhythmias and are generally considered the best possible solution.

What is the purpose of AICD?

Arrhythmia is a disorder of the heart where the beating heart rhythm is not how it usually is supposed to be. It’s either fast or slow or it may be irregular leading to further complications of the heart which may turn out to be life-threatening and/or fatal. Some of the most dangerous arrhythmias are ventricular tachycardia and ventricular fibrillation which have been known to cause cessation in the blood flow and cardiac arrest as well. AICDs are the best and the most effective treatment for such complications and may help in significantly improve a person’s survival probabilities. This device tries to stop any abnormal heart rhythm with a sudden burst of high-speed pacing a.k.a. cardioversion. If cardioversion does not work, the device will then resort to delivering and electrical shock to reset its rhythm a.k.a. defibrillation.

AICD Implantation Procedure

AICD is a permanent device that is used to help the heart with unusual heartbeats. The implantation procedure for AICD is the same as that of the pacemaker’s. The AICD device consists of a generator and electrode lead(s) or wire(s). The generator consists of a, capacitor, programmable software, a battery and a computer chip or circuit with memory (RAM). The generator is usually implanted on the upper left side of the chest under the skin. The electrode wires are connected to the generator and then passed through a vein to the right chambers of the heart. These wires usually get lodged in the septum of the right ventricle. Along with the ability to help in the proper control of the heart rhythm, the AICD device is also capable of collecting and storing data about the heart’s electrical activity for the cardiologist to go through. The differences between pacemakers and AICD devices is that pacemakers are also available as temporary units and are usually used to correct Bradycardia (slow heart rhythm), while the AICDs are most often used as permanent safeguards against fatal arrhythmias.

Types of AICD

The most common types of AICDs used are single chamber AICD, dual chamber AICD and biventricular AICD.

• In a single chamber AICD, the wires are lead into the right ventricle
• If the AICD implantation has dual chambers, the wires are lead to the right ventricle and the right atrium of the heart
• In a biventricular AICD, one of the wires is lead to the right ventricle, one to the right atrium and another wire is placed on the outside wall of the left ventricle

Recent advancements in the medical field have brought about another type of AICD that can be used as well. This AICD is called the subcutaneous ICD or the S-ICD and it has the ability to pace the left ventricle from multiple sites near-simultaneously with multipoint pacing.