Ordinarily, your heart beats at a regular, steady pace called a normal sinus rhythm. It is regulated electrically by the sinus node. However, if certain cells in the lower chamber of your heart (the ventricles) begin to generate their own electrical impulses, these can override the heart’s normal electrical control mechanism. These impulses do not follow the heart’s normal conduction pathway, and may prevent the heart from pumping enough blood and oxygen through the body. One situation, called ventricular tachycardia (VT), may cause you to feel fluttering in the chest or throat or a sensation of dizziness and lightheadedness.
Because less blood is pumped with each beat, your body and brain receive less oxygen-carrying blood, which may result in dizziness, blackouts or fainting, and even unconsciousness. Sometimes VT can be prevented or treated with medications. In other cases, an electrical device is needed to deliver an impulse to the heart to stop the arrhythmia.
When the ventricular arrhythmia becomes even more rapid and unstable, it causes a condition called ventricular fibrillation (VF)-the heart is quivering, and no longer pumps any blood. This leads to cardiac arrest. The only way to correct ventricular fibrillation is to quickly deliver a strong electrical shock to the heart to stop the abnormal rhythm and prompt the heart’s normal electrical conduction system to take over again. This process is called defibrillation.
YOUR IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR
In a hospital or ambulance, when emergencies cause life-threatening arrhythmias, defibrillation is done with an external device called a defibrillator. Paddles are placed against the chest, and a strong electrical impulse is delivered through the heart. However, if your arrhythmia (either ventricular tachycardia or fibrillation) occurs in routine situations, an automatic implantable cardioverter-defibrillator (ICD) can be implanted to monitor and deliver whatever therapy is necessary. It will be programmed to detect and diagnose either ventricular tachycardia or ventricular fibrillation, and will deliver the therapy necessary to correct your abnormal heart rhythms.
Your electrophysiologist may choose to implant a defibrillator in your body to monitor your heart rhythm around the clock and to immediately correct any dangerous arrhythmias should they occur.
The ICD has two components: the generator and the lead(s). The generator is a relatively small, flat, lightweight case that holds a tiny computer and battery. This will generate the electrical impulses used to regulate your heartbeat. The leads are wires covered with soft, flexible plastic. They are connected to the generator and “tell” it how the heart is beating. The leads also transmit the electrical impulses from the generator to the heart.