Which factors may worsen cyanosis in infants with tetralogy of Fallot (TOF)?

Updated: Nov 13, 2018
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Yasmine S Ali, MD, FACC, FACP, MSCI  more...
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Cyanosis generally progresses with age and outgrowth of pulmonary vasculature and demands surgical repair. The following factors can worsen cyanosis in infants with tetralogy of Fallot:

  • Acidosis

  • Stress

  • Infection

  • Posture

  • Exercise

  • Beta-adrenergic agonists

  • Dehydration

  • Closure of the ductus arteriosus

The predominant shunt is from right to left with flow across the VSD into the left ventricle (LV), which produces cyanosis and an elevated hematocrit value. When the pulmonary stenosis is mild, bidirectional shunting may occur. In some patients, the infundibular stenosis is minimal, and the predominant shunt is from left to right, producing what is called a pink tetralogy. Although such patients may not appear cyanotic, they often have oxygen desaturation in the systemic circulation.

Symptoms generally progress secondary to hypertrophy of the infundibular septum. Worsening of the RVOTO leads to RV hypertrophy, increased right-to-left shunting, and systemic hypoxemia.

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