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Heart Rhythm Disorders


The following are some of the more commonly encountered arrhythmias, starting with the supraventricular arrhythmias.

  • Premature atrial contractions (sometimes called PACs, APCs, or premature supraventricular contractions): PACs are an extra heart beat arising from the atria, outside of the SA node, that causes the heart to contract earlier than expected. This is a very common occurrence in all ages and usually is not serious.
  • Supraventricular tachycardia, or paroxysmal SVT: SVTs are regular, rapid heartbeats resulting from abnormal electrical impulses above the ventricle (usually the atria or the AV node).
  • Sick sinus syndrome: This syndrome is characterized by irregular firing of the SA node resulting in both slower and faster-than-normal heart rates.
  • Atrial fibrillation: A common condition caused by electrical impulses discharged at a rapid rate from many different areas of the atria. It usually causes a fast and irregular heartbeat.
  • Atrial flutter: A condition caused by a rapid discharge of abnormal electrical impulses from the right atrium. Typically, the right atrium fires at a rate of 300 beats per minute, but only every other beat is conducted through the AV node, meaning that the ventricular rate is classically 150 beats per minute.

Arrhythmias arising in the ventricle are more likely to be found in people with more serious heart disease but may also be found in healthy individuals.

  • Premature ventricular complex, or PVCs: This abnormal electrical impulse arises from the ventricle, causing the heart to beat earlier than expected. Usually, the heart returns to its normal rhythm right away.
  • Ventricular tachycardia: Fast and usually regular impulses come from the ventricles and cause a very rapid heart rate. This is usually a life-threatening tachycardia and needs immediate medical attention and potentially treatment with an electrical shock or defibrillation.
  • Ventricular fibrillation: Electrical impulses arise from the ventricles in a fast and disordered sequence. The resulting uncoordinated contractions cause the heart to lose its ability to beat and pump blood.  The condition usually causes fainting and collapse, and is fatal if not treated immediately.

Arrhythmias can be frightening, but in many cases, especially in younger patients with normal underlying hearts, they are not life threatening and can be effectively treated with medications.

  • Supraventricular arrhythmias are very common in middle-aged and elderly adults. The older you get, the more likely you are to experience an arrhythmia, especially atrial fibrillation.
  • Many supraventricular arrhythmias are temporary and not serious, especially if no underlying heart disease is present. These arrhythmias are a response to normal activities or emotions.
  • Even if an arrhythmia has a serious underlying cause, the arrhythmia itself may not be dangerous. The underlying problem can often be treated effectively.


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