Definition

Tachycardia is a rapid heart rate of more than 100 beats per minute. Sinus tachycardia, originating from the sinus node (or normal pacemaker in the heart) is a normal response to exercise, illness, or stress.

There are also several types of abnormal tachycardias or arrhythmias . These can originate from the atria (the two smaller chambers on the top of the heart) collectively called supraventricular tachycardias or from the ventricles (the lower chambers of the heart) called ventricular tachycardia .

Tachycardia can be life-threatening. But it can be treated if medical help is provided immediately. So, call for emergency medical help if you think you or someone you know has tachycardia.

Causes

Tachycardias are caused by abnormal conduction of impulses that control heart rhythm.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

The following factors increase your chance of having tachycardia. If you have any of these risk factors, tell your doctor:

• Heart disease, especially a prior heart attack
• Cardiomyopathy —damage to the muscle wall of the lower chambers of the heart
• Electrolyte abnormalities—too much or too little calcium, sodium, magnesium, and potassium in the blood
• Myocardial ischemia—insufficient blood flow to heart muscle tissue
• Hypoxemia—not enough oxygen in the blood
• Acidosis—too much acid in the body’s fluids

Symptoms

If you experience any of these symptoms do not assume it is due to tachycardia. These symptoms may be caused by other, less serious health conditions. If you experience any one of them, see your physician.

• Heart palpitations
• Fast heart rate
• Dizziness
• Lightheadedness
• Fainting or near fainting
• Chest pain
• Shortness of breath

Diagnosis

• Your doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include the following:
  • Electrocardiogram (ECG, EKG ) —a test that records the heart’s activity by measuring electrical currents through the heart muscle
  • Holter Monitor or Event Monitor —an ambulatory monitor to record your heart rhythm that can be worn from 1-30 days to detect arrhythmias and correlate symptoms with the heart rhythm
  • Exercise Test —particularly if the symptoms occur during physical activity
  • Electrophysiology Study —an invasive test where monitoring wires are placed inside the heart and the heart's conduction system is tested directly
  • Cardiac Catheterization —a tube-like instrument inserted into the heart through a vein or artery (usually in the arm or leg) to detect problems with the heart and its blood supply

Treatment

Talk with your doctor about the best treatment plan for you. Treatment options include the following:

Medications

Medications can be utilized including beta-blockers (atenolol, metoprolol, bisoprolol), calcium channel blockers (diltiazem, verapamil) or antiarrhythmics, such as Tambocor (flecainide), Procanbid (procainamide), Cordarone (amiodarone), and Betapace (sotalol), to treat or prevent tachycardia.

Ablation

This is done during an electrophysiology study. The abnormal area of the conduction system is identified and treated with radiofrequency energy or cold energy to destroy the abnormality and potentially cure the arrhythmia.

Cardioversion

This is when an electric shock is applied to the heart to terminate the abnormal rhythm. May be done for life-threatening rhythms such as ventricular tachycardia or ventricular fibrillation or done electively for milder arrhythmias such as atrial fibrillation. Sedation is given so that the patient feels nothing.

Implantable Cardioverter Defibrillator

An implantable cardioverter defibrillator can be surgically placed into your body. It monitors your heartbeat and can apply an electric current when necessary to correct an irregular heartbeat.

Prevention

Reducing risk of heart disease is the best way you can prevent tachycardia. Take the following steps to prevent heart disease:

• Exercise regularly.
• Eat a healthful diet.
• Maintain a healthy weight.
• Stop smoking and avoid secondhand smoke.
• Avoid or limit the intake of caffeine and alcohol.
• Avoid unnecessary stress.
• Have regular physical exams.
• Treat underlying medical problems (eg, high blood pressure , cholesterol problems)

RESOURCES:

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

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

CANADIAN RESOURCES:

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

University of Ottawa Heart Institute
http://www.ottawaheart.ca/UOHI/Welcome.do

References:

Arrhythmia prevention. Heart Rhythm Society website. Available at: http://www.hrspatients.org/patients/risk_factors/default.asp. Accessed April 19, 2007.

Implantable cardioverter defibrillator. American Academy of Family Physicians website. Available at: http://familydoctor.org/270.xml. Accessed April 19, 2007.

Paroxysmal atrial tachycardia (PAT). DynaMed website. Available at: http://dynamed101.epnet.com/Detail.aspx?id=113613. Accessed April 19, 2007.

Ventricular tachycardia. DynaMed website. Available at: http://dynamed102.epnet.com/Detail.aspx?id=115268. Accessed April 19, 2007.

What are arrhythmias? American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=560. Accessed April 19, 2007.

ThirdAge WWW