• Types of Abnormal Heart Rhythms

    Some abnormal heart rhythms (also called arrhythmias) are fast, others are slow and some are irregular. How an arrhythmia is treated depends on the kind of abnormal beat.

    Fast Heart Rhythms (Tachycardia)

    Supraventricular Tachycardia (SVT)

    In the abnormal heart rhythm called supraventricular tachycardia (SVT), the electrical impulse stimulating the heart does not come from the sinus node as it should. Instead, it comes from a collection of tissue involving the atrioventricular (AV) node, and the electrical impulses are generated at a rapid rate, which may result in 280 heart beats per minute.

    Treatment is possible with the Valsalva Maneuver, in which the patient is asked to strain (bear down) in order to slow the heart rate. If this is not effective, medications can be used to slow the heart rate.

    For those with severe SVT, cardioversion may be recommended. In cardioversion, an electrical shock is delivered to the heart to change an abnormal heart rhythm back to a normal rhythm.

    Atrial Flutter

    Atrial flutter occurs when rapidly fired signals cause the muscles in the upper chambers of the heart (the atria) to contract quickly, leading to a very fast and steady heartbeat.

    Treatment with medications is possible. Those with severe atrial flutter may be treated with cardioversion, an electrical shock delivered to a rapidly beating heart to return it to a normal rhythm.

    Ventricular Tachycardia

    Ventricular tachycardia is a dangerous type of rapid heart rhythm usually associated with too little blood being ejected from the heart (poor cardiac output). Ventricular tachycardia arises in the heart’s lower chambers (the ventricles) from tissues that generate a rapid and irregular heart rhythm.

    Ventricular tachycardia is a life-threatening emergency that may require electrical shock therapy called cardioversion.

    Slow Heart Rhythms (Bradycardia)

    Atrioventricular Block (AVB)

    Atrioventricular (AV) block occurs when some or all of the electrical signals traveling from the heart's upper chambers (the atria) to the lower chambers (the ventricles) are impaired or fail to transmit. This is often called "heart block" or "AV block." In this condition, the atria may contract at a normal rate, but the signals to the ventricles are “blocked.”

    There are various types of AV block, depending on the mechanism causing the block. For example,
    • Second-degree AV block occurs when the electrical impulse from the atria is blocked every certain number of beats.
    • In complete AV block, none of the signals pass through the atrioventricular node, leaving the ventricles to generate their own rhythm.
    A pacemaker is a small implanted device that stimulates the heart to beat at a certain rate. It is a recommended treatment for AV block.

    Irregular Heart Rhythms

    Premature Atrial Contraction (PAC)

    In premature atrial contraction (PAC), an electrical impulse generated in the upper chamber of the heart “fires” early. This causes the heart to beat earlier than normal, resulting in an irregular heart rhythm.

    PAC typically does not require therapy. However, if it is severe, medications may be prescribed to control it.

    Premature Ventricular Contraction (PVC)

    In premature ventricular contraction (PVC), the lower heart chambers (the ventricles) generate an early impulse that causes the heart to beat earlier than normal, resulting in irregularity in the heart rhythm.

    PVC typically does not require therapy, particularly if it occurs infrequently. More frequent PVCs require treatment with medications. The cause of PVC should be investigated as it may reflect heart muscle disease.

    Atrial Fibrillation (AF)

    In atrial fibrillation (AF), many sites within the heart’s upper chambers (the atria) generate irregular electrical impulses to cause an irregular heartbeat.

    Atrial fibrillation is unusual in children.

    Electrical shock therapy (h3), in which the heart is “shocked” back into normal rhythm, and medications are used to treat atrial fibrillation.