Reentrant Tachycardias

What is a reentrant arrhythmia?

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Reentrant tachycardias are a family of rapid cardiac arrhythmias caused by abnormal electrical connections in the heart. These abnormal connections form potential electrical circuits, which can disrupt the normal heart rhythm.

The Normal Heart Rhythm

With the normal heart rhythm (which is called normal sinus rhythm), the heart’s electrical impulse originates in the sinus node, and spreads evenly across the heart’s atrial chambers (causing the atria to contract), and then moves on to spread evenly across the heart’s ventricular chambers (causing the ventricles to contract). A little while later (typically, 60 - 100 times per minute), a new electrical impulse is generated by the sinus node, and the whole sequence repeats.

Reentrant Heart Rhythms

Reentrant arrhythmias can occur if an abnormal electrical connection is present in the heart — that is, an electrical pathway that isn’t supposed to be there, connecting two areas that should not be connected. Abnormal electrical connections can be congenital, or they can form as a result of heart disease. If such a connection exists, it can form an electrical circuit. 

When such a potential circuit is present in the heart, a reentrant arrhythmia becomes possible. A reentrant arrhythmia occurs if one of the heart’s electrical impulses (either a normal sinus node impulse, or an abnormal electrical impulse generated by a premature atrial complex (PAC) or a premature ventricular complex (PVC)), enters the circuit under just the right conditions. Such an impulse can become “captured” within the circuit, in such a way that it begins begins spinning around the circuit, over and over again. With each lap around the circuit, the impulse produces a new heart beat. This new, abnormal rhythm is called a reentrant arrhythmia (because the electrical impulse “re-enters” the circuit with each lap). 

Since there is no pause between heart beats during a reentrant arrhythmia (because the impulse spins continuously around the circuit), typically the heart rate during a reentrant arrhythmia is quite rapid. That is, tachycardia occurs. 

Most typically, when a reentrant tachycardia occurs its onset is quite sudden, as is its termination. People often describe their symptoms with these arrhythmias as starting and stopping instantaneously, as if turning on and off a light switch. Depending on the kind of arrhythmia it produces and its rate, symptoms with a reentrant tachycardia may vary between mild palpitationsand syncope, or even sudden death.

Types of Reentrant Tachycardia

There are two broad categories of reentrant tachycardias - supraventricular tachycardia (SVT); and ventricular tachycardia (VT) and ventricular fibrillation (VF).

Reentrant Supraventricular Tachycardias

The abnormal electrical connections which cause SVT most often are present from birth — so these arrhythmias are usually seen in healthier, younger people. Reentrant SVT can cause significant symptoms, but is only rarely dangerous or life-threatening. The different varieties of SVT are generally named according to the nature of the reentrant circuit that produces them. The major kinds of SVT include:

Atrial fibrillation is different from other kinds of reentrant SVT in that it is usually not due to a congenital abnormality of the heart’s electrical system, but rather is often caused by the development of underlying heart problems. Atrial fibrillation is therefore more often seen in older individuals than are the other kinds of SVT.

Reentrant Ventricular Tachycardias

In contrast to SVT, the extra electrical connections that produce VT or VF are usually not present from birth. Instead, these connections result from the scarring of heart muscle that occurs with some types of heart disease (especially coronary artery disease — CAD — or heart failure).

This means that the people who are prone to develop VT or VF are usually older, and tend to have significant underlying heart disease. Unfortunately, the risk of having VT or VF is common in CAD and heart failure, and is the reason why so many people with these conditions experience sudden cardiac death.

Treatment of Reentrant Tachycardias

The treatment of a reentrant tachycardia depends on the specific type of arrhythmia that is present, and the symptoms it is causing. If the arrhythmia occurs only very rarely, lasts only a few seconds, and causes trivial symptoms, perhaps no treatment is needed at all. Life threatening arrhythmias require aggressive treatment. 

A Word From Verywell

Reentry is a common mechanism of both atrial and ventricular tachycardias, and reentrant tachycardias, which can occur at any age, can vary in significance between a mild annoyance to life-threatening. Anyone with unexplained episodes of tachycardia should be evaluated by their doctor.

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Article Sources

  • Fogoros RN, Mandrola JM. Abnormal Heart Rhythms. In: Fogoros’ Electrophysiologic Testing. 6th Edition, Wiley Blackwell, Oxford, UK 2018.

  • Link MS. Clinical practice. Evaluation and initial treatment of supraventricular tachycardia. N Engl J Med 2012; 367:1438.

  • Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Heart Rhythm 2016; 13:e136.