Implantable Cardiac Defibrillator (cont.)

How can ventricular tachycardia and fibrillation be treated and prevented?

Medications have traditionally been used in preventing ventricular tachycardia and fibrillation. Examples of these medications include Pronestyl and Cordarone and beta-blockers such as Tenormin and Inderal. Medicines, however, are not always successful in preventing tachycardias or in terminating tachycardias once they occur.

Once a life threatening tachycardia occurs, the most effective treatment is to administer mild electric shock(s) to the heart to terminate the tachycardia and reset the heart rhythm to normal.

If a patient is in cardiac arrest due to ventricular fibrillation, the treatment is the delivery of a strong electrical shock to the fibrillating heart without delay. Irreversible brain and other organ damages can occur within minutes if the normal heart rhythm is not restored. Most patients can potentially be saved if shocks are delivered quickly to convert the fibrillation to normal rhythm before irreversible brain damages occur.

The electrical shocks (mild and strong) that terminate ventricular tachycardia and fibrillation can be delivered by an external defibrillator (a portable unit with pads that deliver electrical shocks to the heart), or by an implantable cardiac defibrillator (ICD). External defibrillators, however, may not be readily available, and rescuers may not be able to administer effective CPR for long periods before paramedics arrive. Therefore, in patients known to be at risk of developing life-threatening tachycardias, ICDs can be implanted in their chests as a preventive measure to terminate tachycardias and fibrillation and avert cardiac arrest.

Who should receive an ICD?

Patients at risk of developing sudden cardiac arrests due to ventricular tachycardias and fibrillations are candidates for ICDs. ICDs do not prevent the occurrence of life-threatening rhythms, but can quickly terminate them when they occur. Recent clinical trials have identified several groups of patients who should receive ICDs. They are:

• Patients who have survived cardiac arrest;
• Patients with ventricular tachycardias that significantly decrease the amount of blood delivered by the heart, resulting in low blood pressure;
• Patients with significant heart muscle damage from prior a heart attack, and have ventricular tachycardia episodes that are not suppressed by medications; and
• Patients deemed at high risk for sudden death from cardiac arrest based on a history of heart disease and findings from an electrophysiologic evaluation (special study of the electrical system of the heart).

Source: MedicineNet.com
http://www.medicinenet.com/implantable_cardiac_defibrillator/article.htm