• Kinds of Abnormal Heart Rhythms

     
     
     
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    11/16/2009

    Some abnormal heart rhythms are fast, others are slow and some are irregular. How an arrhythmia is treated depends on the kind of abnormal beat.  Read more about arrhythmias that most commonly develop in children and young adults:

    • Fast heart rhythms
    • Slow heart rhythms
    • Irregular heart rhythms 

    Fast Heart Rhythms (Tachycardia)

    Supraventricular Tachycardia (SVT)

    In this abnormal heart rhythm, the impulse stimulating the heart does not come from the sinus node. Instead, it comes from a collection of tissue involving the atrioventricular (AV) node.  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, or 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

    This condition occurs when rapidly fired signals cause the muscles in the atria to contract quickly, leading to a very fast and steady heartbeat.  Treatment is possible through the use of medications.  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

    This is a dangerous type of rapid heart rhythm usually associated with poor cardiac output (amount of blood ejected from the heart).  It arises in the heart’s lower chambers (ventricles) from tissues that generate a rapid and irregular heart rhythm.  Ventricular tachycardia is a life-threatening emergency that may require electrical shock therapy (cardioversion).

    Slow Heart Rhythms (Bradycardia)

    Atrioventricular Block (AVB)

    AV block occurs when some or all of the electrical signals traveling from the heart's upper chambers (atria) to the lower chambers (ventricles) are impaired or fail to transmit.  This is "heart block" or "AV (atrioventricular) block."  In this condition, the atria (upper chambers) may contract at a normal rate, but the signals to the ventricles are “blocked.”  There are various types of AV block depending upon the mechanism of 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, a small implanted device that stimulates the heart to beat at a certain rate, is a recommended treatment for AV block.

    Irregular Heart Rhythms

    Premature Atrial Contraction (PAC)

    In this condition, an impulse generated in the upper chambers “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 PVC, the ventricles (lower heart chambers) generate an early impulse which causes the heart to beat earlier than normal, resulting in irregularity in the heart rhythm. It 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 AF, which is unusual in children, many sites within the heart’s upper chambers generate irregular electrical impulses to cause an irregular heart beat.  Electrical shock therapy (cardioversion), in which the heart is “shocked” back into normal rhythm, and medications are used to treat AF.