Re-entry ventricular arrhythmia is a type of
paroxysmal tachycardia occurring in the
ventricle where the cause of the
arrhythmia
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adult ...
is due to the electric signal not completing the normal circuit, but rather an alternative circuit looping back upon itself. There develops a self-perpetuating rapid and abnormal activation. ("Circus Movement" is another term for this.) Conditions necessary for re-entry include a combination of unidirectional block and slowed conduction.
[Am J Cardiol. 1984 Jul 30;54(2):1A-6A.] Circus movement may also occur on a smaller scale within the AV node (dual AV nodal physiology), a large bypass tract is not necessary.
Re-entry is divided into two major types:
natomically Definedre-entry and
unctionally Definedre-entry. The circus movement can occur around an anatomical or functional core. Either type may occur alone, or together.
''Anatomically'' defined re-entry has a fixed anatomic pathway. Anomalous conduction via accessory pathways (APs) creates the re-entry circuit (which are also called bypass tracts), that exists between the atria and ventricles.
Wolff–Parkinson–White syndrome (WPW) is an example of anatomically defined re-entry. WPW syndrome is an atrioventricular re-entrant tachycardia (AVRT), secondary to an accessory pathway that connects the epicardial surfaces of the atrium and ventricle along the AV groove.
[Hurst's The Heart, 13e.(2011). Chapter 41. Supraventricular Tachycardia: Atrioventricular Nodal Reentry and Wolff-Parkinson-White Syndrome.] The majority of time symptomatic WPW fits the definition of AVRT (
Supraventricular tachycardia) however
AVNRT (dual AV nodal physiology) exist in ~10% of patients with WPW syndrome creating the possibility of spontaneous atrial fibrillation degenerating into ventricular fibrillation (VF). The fact that WPW patients are young and do not have structural heart disease, lead to using catheter ablation of the APs with the elimination of the atrial fibrillation as well as the episodes of re-entrant ventricular tachycardia. This elimination of the atrial fibrillation with ablation implies APs have some pathophysiologic role in the development of a-fib in the WPW patient.
''Functionally'' defined re-entry does not require the alternative anatomically defined circuit accessory pathways and it may not reside in just one location.
Ventricular fibrillation
Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and n ...
(VF) following
ventricular tachycardia
Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...
(VT) may be described as a functionally defined re-entry problem caused by multiple mini re-entrant circuits spontaneously created within the ventricular myocardium. The original re-entrant circuit breaks down into multiple mini reentrant circuits.
[Hurst's The Heart, Chapter 38. Mechanisms of Cardiac Arrhythmias and Conduction Disturbances. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds)] (VF becoming the grand finale of a single prolonged VT larger circus movement, propagating change in the "functional core" of the ventricular myocardium, dissipating mini reentrant circuits, exhibited as ventricular fibrillation.) Ischemia, electrolyte, pH abnormalities, or bradycardia are potential causes of functionally defined re-entry due to changes in the properties of the cardiac tissue's functional core.
(No accessory pathway required).
For reentry to occur, the path length of circuit should be greater than the wave length (ERP × conduction velocity) of impulse.
See also
*
AV reentrant tachycardia
*
AV nodal reentrant tachycardia
References
External links
{{Medical resources
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Cardiac arrhythmia