Rhythm Interpretation: Reentry
Wednesday, December 31, 2025
Rhythm Interpretation: Reentry
Pearls of Knowledge © BrainyNurses.com
Reentry is one of the most common causes of supraventricular and ventricular rhythms. It is seen with atrial fibrillation, atrial flutter, and runs of beats, such as in ventricular tachycardia or paroxysmal atrial tachycardia.
Typically, the myocardial tissue is depolarized and then becomes refractory. However, in a patient with structural heart disease, or scar tissue from ischemia or infarction, as the impulse is released, not all of the myocardium is ready to accept it.
The impulse may move through a moderately depressed area while a severely depressed area is not yet ready to accept it. When the impulse reaches the end of the moderately depressed area, the adjacent severely depressed area may now be ready to accept it. Reentry occurs when a portion of the tissue is reactivated by an impulse that had already stimulated it.
Local Reentry
Local reentry occurs within a small area (single site) of the atrium or ventricle such as atrial flutter, ventricular tachycardia, or paroxysmal atrial tachycardia. In atrial fibrillation, multiple reentry circuits are present resulting in chaotic P waves.
Atrial flutter
(Most often occurs at atrial rates of 300 BPM but can range from 250-450 BPM.)
Ventricular tachycardia
(Heart rate generally between 140-200 BPM.)
Paroxysmal atrial tachycardia
(Heart rate generally between 120-250 BPM.)
Atrial fibrillation
(Ventricular rate varies depending on the degree of AV block.)
Global Reentry
Global reentry involves activation of the entire conduction system and is seen in Wolff-Parkinson-White (WPW). In WPW, there are one or more accessory pathways. When an impulse occurs, it enters the ventricles by going through the AV node and the accessory pathway. This results in a short PR interval, a delta wave (slurring of the QRS), and a wider QRS complex because of early activation of the ventricular myocardium by the accessory pathway and the spread of the wave of depolarization.
When an early beat occurs, the “normal” conduction (which is the AV node) is refractory. This allows the impulse to go up or down just the pathway and results in a supraventricular tachycardia.
When it goes up the pathway to reenter the atria, it is a narrow complex.
When it goes down the pathway but then reenters the atria via the AV node, it is a wide complex, is difficult to distinguish from ventricular tachycardia, and is more dangerous.
WPW in sinus rhythm
(Short PR, delta wave, and wide QRS)
WPW in reentry (and resultant narrow complex supraventricular tachycardia)
WPW in reentry (and resultant wide complex supraventricular tachycardia)
Summary
Reentry is a common cause of supraventricular and ventricular rhythms. It may be local reentry in rhythms such as atrial flutter, ventricular tachycardia, or paroxysmal atrial tachycardia. In atrial fibrillation, there are multiple reentry sites.
Global reentry involves the entire conduction system and is seen in WPW. Most often, the tachycardia is narrow complex because the impulse goes down through the AV node and up through the pathway. Wide complex is uncommon and dangerous. It occurs when the impulse goes down through the pathway and up through the AV node.
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