What is the pathophysiology of pediatric atrial flutter?

Updated: Feb 04, 2019
  • Author: M Silvana Horenstein, MD; Chief Editor: Syamasundar Rao Patnana, MD  more...
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Atrial flutter is a reentrant arrhythmia circuit confined to the atrial chambers. As a rule, atrial flutter originates in the right atrium, whereas atrial fibrillation, which is more frequent in adults, originates in the left atrium.

A flutter circuit typically surrounds an anatomical or functional barrier and includes a zone of slow conduction (or conduction over an extended circuit) and an area of unidirectional block, as required for reentry of all types. Frequently, a premature beat blocks one limb of the circuit and is sufficiently delayed in the other limb (while traversing around the anatomical or functional barrier) to allow for recovery from refractoriness in the first limb.

The reentrant circuits that occur in children with atrial flutter after congenital heart disease surgery are believed to involve abnormal atrial tissue that has been subject to chronic cyanosis, inflammation secondary to surgery, scarring, and increased wall stress in cases of enlarged atria. Such circuits may encircle anatomical barriers such as atriotomy scars or surgical anastomoses, and they may use areas of slow conduction along baffle limbs and other sites of injury in addition to the tricuspid valve–coronary sinus isthmus.

Sinus node dysfunction with bradycardia is generally present in many of these patients years after surgery. This is a contributing factor for development and maintenance of atrial flutter.

Atrial flutter circuits in children with congenital heart disease are typically more variable than those seen in adults. For the most part, atrial flutter circuits in adults are confined to the tricuspid valve–coronary sinus isthmus (or isthmus-dependent flutter).

In the fetus, atrial flutter occurs mainly during the third trimester, although it can occur as early as midgestation. [4] The atrium is believed to reach a critical mass to support an intra-atrial macroreentry circuit at about 27-30 weeks’ gestation. One study demonstrated an association between fetal atrial flutter with atrioventricular reciprocating tachycardia and accessory pathways. They also found that, compared to the neonate, accessory pathways in the fetus had a greater propensity for spontaneous, natural conduction, a finding that may indicate accessory pathways often become nonfunctional at late stages of fetal development. [4]

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