Antiarrhythmics are medications used to treat arrhythmias, abnormal heart rhythms resulting from a disturbance in the heart’s electrical system. Antiarrhythmic medications are frequently used in the setting of rapid heartbeats. The most common tachyarrhythmias treated with antiarrhythmics include:

• Atrial tachycardia and atrial fibrillation. These conditions occur when the upper chambers of the heart (atria) beat too rapidly and at times irregularly. These tachyarrhythmias are generally not immediately life-threatening, but do increase the risk of stroke because blood clots can form in the atria and travel into the brain.
  
  
• Ventricular tachycardia. This is a rapid heart rhythm that occurs in the lower chambers of the heart (ventricles). Ventricular tachycardia can be very dangerous if it progresses to ventricular fibrillation (see below).
  
  
• Ventricular fibrillation. This occurs when the ventricles beat in a very chaotic and loosely organized fashion. Ventricular fibrillation is a serious, life-threatening condition that must be corrected immediately or death will likely result. Antiarrhythmic medications are sometimes prescribed to prevent ventricular fibrillation. In recent years, implantable cardioverter defibrillators (ICDs) have become common in the prevention and immediate treatment of ventricular fibrillation. These devices are implanted inside the chest. They monitor the heart rhythm, and in the event of ventricular fibrillation, they administer an electric shock to jolt the heart back into a normal rhythm. The device is similar to the defibrillators carried by emergency paramedic crews. ICDs and antiarrhythmic medications are often used in the same patient. ICDs are also frequently implanted in patients who are at risk of ventricle tachycardia.

Abnormally slow heart rhythms (e.g., bradycardia) are not typically treated with antiarrhythmic medications. Bradycardia can be caused by disease of the heart’s electrical system. It may also result from certain medications (e.g., beta blockers, calcium channel blockers). In trained athletes, low heart rhythms may actually be a sign of a healthy heart. When bradycardia is due to heart disease, and the patient has symptoms (e.g., dizziness, fainting), it is best treated with the implantation of a pacemaker.

Researchers continue to evaluate the role of antiarrhythmics in arrhythmia treatments, especially as ICDs become more popular. In recent years, their use has expanded, and multiple studies have been conducted to determine how antiarrhythmics fit with ICD therapy. In some cases, patients will need to take antiarrhytmics for life even after an ICD has been implanted.