Left atrial isomerism (polysplenia)

Cardiac malformations

  • Dextrocardia (30%)
  • CAVC (50%) or cleft MV (20%), either have frequent left ventricular outflow tract obstruction; rarely, transposition of the great arteries, pulmonary stenosis (30-40%) or subaortic stenosis (22%). DORV in 40%. L-looped ventricles in 10-30%, in whom dual AV nodes are more common. Rarely exhibits subaortic conus.
  • Interrupted inferior vena cava with azygos continuation, in which the renal to suprahepatic segment of the IVC is absent and a dilated azygos vein continues from the renal veins to the SVC. The hepatic veins drain directly to the floor of the atrium (singularly or multiply)
  • Bilateral superior venae cavae
  • Pulmonary veins draining to ipsilateral atria or to RA due to malposition of septum primum (40-70%); connection to a systemic vein is rare.
  • Both atria have morphologic features of a left atrium (continuity between the vestibule of the atrioventricular junction and the smooth-walled venous component of the atrium without the interposition of pectinate muscles).
  • Congenital complete heart block (7%)
  • Unroofed coronary sinus (30-50%)

General considerations

Newborn period: Polysplenia is generally associated with less complex heart disease than asplenia, although there are many exceptions. In the absence of severe subaortic obstruction or PS, intervention in the newborn period may not be required. If the ventricles are well balanced, patients may undergo biventricular repair as their initial operation including complex atrial septation.

Single ventricle palliation considerations: When the CAVC is unbalanced, the initial operation may be a PAB (with aortic arch reconstruction if needed) followed by a cavopulmonary anastomosis. In the setting of interrupted IVC, this procedure is termed a Kawashima procedure; all systemic venous return is diverted to the pulmonary circulation except for hepatic venous return. In this instance, the ‘hepatic factor’ is diluted and rendered ineffective prior to passing through the pulmonary circulation, which causes the eventual formation of pulmonary arteriovenous fistulae (and can cause severe refractory hypoxemia). The treatment for this is a surgical diversion of hepatic veins to the azygous vein. This procedure may result in transient hepatitis and coagulopathy (due to hepatic venous hypertension). Anticoagulation is paramount following this operation, as is vigilant monitoring of patency of this graft.

Extracardiac manifestations

  • The spleen composed of a cluster of small splenuli, a large spleen and several small ones, or may be multilobed. Because functional asplenia commonly develops, all patients should be vaccinated against pneumococcus and regularly screened for Howell-Jolly bodies; when present, should be treated with PCN (e.g. amoxicillin) prophylaxis for life. Risk of infections is life-long, perhaps highest in newborn period.
  • Gastrointestinal anomalies are common and include intestinal malrotation (40-90%); an abdominal ultrasound is necessary in the newborn period. When malrotation is present, a Ladd’s procedure may be performed following critical congenital heart surgery to decrease the risk of midgut volvulus. Biliary atresia (11%) may also occur in polysplenia, and has a significant impact on prognosis when present; initial intervention includes a Kasai procedure.
  • Bilateral bilobed lungs with hyparterial bronchi
  • Genitourinary abnormalities (6%), including cryptorchidism.
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