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Arrhythmia Medications
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by Mary Calvagna, MS

Definition

In ventricular fibrillation, the heart’s ventricles contract in a rapid and unsynchronized manner. The ventricles are the main pumping chambers of the heart, and their beating is responsible for moving blood to the organs and tissues of the body. During ventricular fibrillation, little or no blood is pumped from the heart. Unless medical help is provided immediately, ventricular fibrillation will lead to cardiovascular collapse and sudden death.

Causes

Causes of ventricular fibrillation include:

• Inadequate blood flow to the heart due to coronary artery disease (CAD)
• Scar tissue within the heart due to previous injury to heart, such as a heart attack (myocardial infarction)
• Congestive heart failure (CHF)
• Infection of the heart muscle (myocarditis)
• Shock
• Electrical shock
• Drowning
• Dangerously low body temperature (hypothermia)
• Electrolyte imbalance (eg, very low levels of potassium or magnesium in the blood)
• Drugs that affect the electrical currents of the heart (eg, sodium or potassium channel blockers)
• Low atmospheric oxygen

Risk Factors

Ventricular fibrillation is most commonly associated with CAD. Therefore, the factors that can increase one’s risk of CAD can increase the risk of ventricular fibrillation.

The following factors increase your chance of developing ventricular fibrillation. If you have any of these risk factors, tell your doctor:

• CAD
• CHF
• Heart rhythm disorder (ie, arrhythmia), especially multiple premature ventricular beats
• Previous heart attack
• Previous ventricular fibrillation
• High blood pressure
• Diabetes
• Smoking
• Excessive use of alcohol
• Drug abuse
• Stress
• High cholesterol (dyslipidemia)
• Obesity
• A high-fat diet
• A family history of cardiovascular disease
• Advancing age

Symptoms


Ventricular fibrillation happens without warning. When it occurs, symptoms may include:

• Loss of consciousness within seconds
• Sudden collapse
• Seizures
• Loss of color in the skin
• Dilated pupils
• No detectable pulse, heartbeat, or blood pressure

Diagnosis

Ventricular fibrillation is suspected when a person collapses suddenly and has no detectable pulse or heartbeat. The diagnosis is confirmed by electrocardiography (ECG). ECG records the heart’s activity by measuring electrical currents through the heart muscle.

Treatment

Ventricular fibrillation must be treated as an extreme emergency and treatment must be administered within 4-6 minutes.

Cardiopulmonary Resuscitation (CPR)

CPR is a combination of rescue breathing and chest compressions. CPR is a temporary procedure that can help maintain some blood flow to the brain, heart, and other vital organs until trained medical personnel are available to provide more advanced treatment.

Defibrillation

In defibrillation, an electronic device is used to give an electric shock to the heart. The electric shock helps to re-establish the normal contraction rhythms of the heart. An automated external defibrillator (AED) is a portable defibrillation device. Most ambulances carry AEDs. They are also frequently found in many public places, such as sports complexes.

CPR should be started immediately and followed by defibrillation as soon as defibrillation equipment is available.

If defibrillation fails three times, the drug epinephrine is given intravenously followed by repeated defibrillation.

Anti-arrhythmic Drugs

Anti-arrhythmic drugs, such as amiodarone, lidocaine, and procainamide, may be given intravenously with continued resuscitation attempts when a person continues to fibrillate.
If the heart’s rhythm is stabilized by defibrillation, anti-arrhythmic drugs can be given to maintain the heart’s rhythm.

Implantable Cardioverter Defibrillator

An implantable cardioverter defibrillator (ICD) can be surgically placed in the chest to help prevent ventricular fibrillation. An ICD continuously monitors the heart’s rhythm. If it detects an abnormal beat, it sends electrical impulses to restore the heart’s normal rhythm.

Prevention

To help reduce your chance of getting ventricular fibrillation, take the following steps:
Lower your risk of CAD:

• Eat a healthful diet, one that is low in saturated fat and rich in whole grains, fruits, and vegetables.
• Exercise regularly.
• If you are overweight, lose weight.
• Don’t smoke. If you smoke, quit.
• Avoid or limit your intake of caffeine, alcohol, and other substances that may contribute to arrhythmias or heart disease.
• Avoid unnecessary stress, and try to manage or control stressful situations that cannot be avoided.

If a person is at high risk of ventricular fibrillation, an implantable cardioverter defibrillator (ICD) can be surgically placed in the chest to help prevent ventricular fibrillation. In addition, anti-arrhythmic drugs may be given to prevent a future episode.

RESOURCES:
American Heart Association
http://www.americanheart.org

Heart Rhythm Society
http://www.hrspatients.org

National Heart, Lung, and Blood Institute
http://www.nhlbi.nih.gov

CANADIAN RESOURCES:
Canadian Cardiovascular Society
http://www.ccs.ca

National Stroke and Heart Foundation of Canada
http://ww2.heartandstroke.ca

REFERENCES:

ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Circulation. 2006;114:e385.

Beers MH, Berkow R. The Merck Manual of Diagnosis and Therapy. 17th ed. Hoboken, NJ: John Wiley and Sons, Inc.; 1999.

Braunwald E, Zipes DP, Libby P. Heart Disease: A Textbook of Cardiovascular Disease. 6th ed. Philadelphia, PA: WB Saunders Company; 2001.

Cardiopulmonary resuscitation (CPR). American Heart Association website. Available at: http://www.americanheart.org/presenter.j.... Accessed August 7, 2005.

Defibrillation. American Heart Association website. Available at: http://www.americanheart.org/presenter.j.... Accessed August 7, 2005.

Marx JA. Rosen's Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, MO: Mosby, Inc.; 2002.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, PA: WB Saunders Company; 2002.

Risk factors and prevention. Heart Rhythm Society website. Available at: http://hrspatients.org/patients/risk_fac.... Accessed August 7, 2005.

Last reviewed December 2007 by J. Peter Oettgen, MD

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Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.