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Arrhythmias in a hall of mirrors: Pediatric heterotaxy syndromes

Published:December 28, 2020DOI:https://doi.org/10.1016/j.hrthm.2020.12.028
      Heterotaxy comes from the Greek words heteros, meaning “other than,” and taxis, meaning “arrangement.” It is thought to be caused by an embryological failure to differentiate along the right-left axis and can affect the thoracic and abdominal visceral organs. There are several different classification schemes that are beyond the scope of this commentary, but in short, they can be generally divided into “asplenia/polysplenia,” “right atrial isomerism/left atrial isomerism” based on morphology of the atrial appendages, and those that are not clearly mirror image reflections of the right and left sidedness, simply stated as “heterotaxy” or “indeterminate.”
      • Jacobs J.P.
      • Anderson R.H.
      • Weinberg P.M.
      • et al.
      The nomenclature, definition and classification of cardiac structures in the setting of heterotaxy.
      While it is not as simple as a duplication or mirror image of the right or left atria, the terminology is based more on the appearance of the appendages, yet the terms right/left atrial isomerism is often used for brevity even if not entirely anatomically accurate. These congenital failures of laterality often include complex congenital heart defects including unique structural and electrical abnormalities. The electrophysiological manifestations of heterotaxy syndromes can affect all levels of the conduction system, include sinus and atrioventricular (AV) nodes as well as atrial and ventricular tachyarrhythmias. In general (although there are always exceptions to the rules), those patients with right atrial isomerism tend to have duplicated sinus and AV nodes, leading to a propensity to supraventricular tachycardias including twin AV node tachycardia, whereas those with left atrial isomerism may be lacking the normal sinus and/or AV nodal tissue, leading to a propensity to sinus node dysfunction and/or AV block.
      • Ozawa Y.
      • Asakai H.
      • Shiraga K.
      • et al.
      Cardiac rhythm disturbances in heterotaxy syndrome.
      Many patients with heterotaxy syndrome require complex cardiac surgical repairs, which can also predispose to postoperative arrhythmias and conduction abnormalities.
      • Marathe S.P.
      • Zannino D.
      • Cao J.Y.
      • et al.
      Heterotaxy is not a risk factor for adverse long-term outcomes after Fontan completion.
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