Tachycardias - The Fast Heart Rhythms

tachycardia
Tachycardia. Artpartner-Images/Getty Images

Tachycardia is the name given to any heart rhythm that produces a rapid heart beat.

Normal Tachycardia - Sinus Tachycardia

Tachycardia is most often completely normal. In fact, nearly all of us have it nearly every day. Increasing the heart rate is the main way the heart is able to increase the amount of blood it is pumping during periods of exertion or stress. This normal kind of tachycardia, which is produced by the sinus node, is called sinus tachycardia.

The Abnormal Tachycardias - Cardiac Arrhythmias

However, there are also several kinds of cardiac arrhythmias (abnormal heart rhythms) that cause tachycardia.

There are two general types of arrhythmias that produce tachycardia: the supraventricular tachycardias, which arise in the atria of the heart, and the ventricular tachycardias, which arise in the ventricles. These two types of tachycardia are quite different both in the types of people they usually affect, and in the amount of danger they pose.

Supraventricular Tachycardias

Most types of supraventricular tachycardias (SVT) typically occur in young, otherwise healthy people. (The main exception is atrial fibrillation, which is much more common in older people.)

SVT tends to occur as episodes that begin and end quite suddenly, usually without any warning whatsoever. SVT commonly causes significant palpitations, anxiety, lightheadedness or dizziness, weakness, and sometimes shortness of breath.

People who have SVT usually have no symptoms at all in between episodes. But if episodes occur frequently or last for a long time, SVT can prove quite disruptive to a person’s life.

Despite how badly SVT can make you feel, however, it almost never poses a significant risk to life and limb.

    There are many different varieties of SVT. The most common of these are:

    In addition to these common varieties, there are several kinds of SVT that are much less common. You can read about these less common types of SVT here.

    SVT can almost always be treated effectively. Anyone who has SVT should seek medical care with a cardiac rhythm specialist.

    Ventricular Tachycardias

    The ventricular tachycardias include two general kinds of arrhythmia: ventricular tachycardia itself, and ventricular fibrillation. In most cases, these arrhythmias are seen in older people who have significant underlying cardiac disease, especially coronary artery disease (CAD) and heart failure.

    Ventricular fibrillation (VF) is the most dangerous of the cardiac arrhythmias. When it occurs it invariably leads to death within a few minutes unless it is stopped.

    In VF, the electrical impulses within the ventricles suddenly become completely chaotic, the heart immediately stops beating, and a cardiac arrest occurs. Unless the victim receives effective cardiopulmonary resuscitation, death ensues within minutes. Ventricular fibrillation is estimated to cause over 300,000 sudden deaths each year in the U.S. alone. Obviously, the best way to deal with ventricular fibrillation is to prevent it.

    Ventricular tachycardia is another potentially dangerous arrhythmia originating in the ventricles. While in some people ventricular tachycardia produces only minimal symptoms, more often it produces significant palpitations, severe lightheadedness or loss of consciousness, or sudden death. In contrast to ventricular fibrillation, in many cases ventricular tachycardia allows the heart to continue pumping to at least some extent. So sudden death may not be immediate, and may not occur at all.

    The large majority of people with ventricular tachycardia have this arrhythmia as a result of CAD or heart failure.

    However, there are much less common types of ventricular tachycardia that occur in people who are young and otherwise healthy. These types of ventricular tachycardia include:

    Because all forms of ventricular tachycardia are potentially lethal, anyone with this arrhythmia - no matter what the cause - needs to be evaluated by a specialist in cardiac arrhythmias.

    Sources:

    Blomström-Lundqvist C, Scheinman MM, Aliot EM, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Supraventricular Arrhythmias). Circulation 2003; 108:1871.

    Zipes, DP, Camm, AJ, Borggrefe, M, et al. ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death-Executive Summary A Report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death). J Am Coll Cardiol 2006; 48:1064.

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