Moffitt Cardiology Report Pearls: Cardiac manifestations of Down syndrome, IBS

Take-home pearl: complete AVSD (atrioventricular septal defect) is the most common cardiac defect in patients with Down syndrome.


Cardiac manifestations of Down syndrome: occurs in about ½ of patients with Down syndrome, depending on the study. Here are the most common defects, and a significant proportion of patients had more than one anomaly

  • Complete atrioventricular septal defect (CAVSD) – 37 percent
  • Ventricular septal defect (VSD) – 31 percent
  • ASD – 15 percent
  • Partial atrioventricular septal defect (PAVSD) – 6 percent
  • Tetralogy of Fallot (TOF) – 5 percent
  • PDA – 4 percent


As a result of these cardiac anomalies, you can sometimes see

  • Pulmonary HTN (unless there is associated pulmonary stenosis as a “protective” malformation that prevents pulm HTN like in Tetralogy of Fallot)
  • Polycythemia: don’t need phlebotomy since that is an appropriate physiologic response to chronic hypoxia
  • Paradoxical emboli due to septal defects


Differential cyanosis: cyanosis and hypoxia in the lower extremities, but not in the upper extremities or head. This occurs with patent PDA and Eisenmenger syndrome (R to L shunt). The reason this takes place is because the PDA connects the PA to the aorta after the take-off of the L subclavian. When the R to L shunt occurs, the deoxygenated blood will go from the PA to the aorta after the L subclavian and cause these lower extremities to be cool, cyanotic and hypoxic.


IBS: from our MKSAP question, we were wondering what the first-pass work-up should be in IBS

  • CBC: screen for anemia (would be a red-flag) or infection
  • Chem panel: Can check in diarrhea-predominant IBS to r/o electrolyte abnormalities
  • Lactose-free diet x1 week in conjunction with lactase supplements
  • Additional testing depends on if diarrhea or constipation predominant and should be guided by history. Tests to consider for diarrhea-predominant IBS
    • O&P, stool culture, stool leukocytes: little role if chronic diarrhea with Giardia being the one exception if the patient has appropriate exposure
    • Tissue transglutaminase: recommended for IBS-D
    • 24hr stool collection: if osmotic, malabsorptive or secretory diarrhea is suggested by history
    • Endoscopy: if history concerning for microscopic colitis
    • Breath test for bacterial overgrowth

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