Pulse ox screening for critical congenital heart disease
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Critical congenital heart disease (CCHD), defined as heart disease requiring either surgical or catheter-based intervention in the first year of life, affects 2-3 out of every 1,000 live births. Specific defects include hypoplastic left heart syndrome, pulmonary atresia, tetralogy of Fallot, total anomalous pulmonary venous return, transposition of the great arteries, tricuspid atresia, and truncus arteriosus. The majority of CCHD is identified prior to discharge from the newborn nursery. Many patients have already been detected prenatally. A good portion of those not identified prenatally will present with signs or symptoms in the first 24 hours of life. These may include an audible murmur, abnormal heart sounds, the absence of palpable pulses, cyanosis, pallor, or tachypnea. Nevertheless, a small percentage of patients with CCHD may inevitably "slip through the cracks." Usually these are infants with ductal-dependent heart lesions whose ductus arteriosus has remained open and therefore either have sufficient pulmonary blood flow to prevent the noticeable detection of cyanosis, or have sufficient cardiac output to prevent signs of shock. It almost all cases, however, these patients will have a level of oxygen desaturation that may identify them as potential "risks" despite appearing normal to an examiner's eye.
The use of routine pulse oximetry has been proposed as a method to screen newborns for unrecognized CCHD prior to discharge from the newborn nursery. In 2011, the American Heart Association and American Academy of Pediatrics endorsed universal screening with pulse oximetry in all newborns after 24 hours of age, concluding that routine pulse ox screening 1) is effective in identifying CCHD, and 2) incurs very low cost and risk of harm.
Subsequently, the state of Texas passed House Bill 740 on June 14, 2013, requiring pulse oximetry screening to be added to the panel of routine screenings received by all newborns born in the state of Texas. The law went into effect earlier this month.
Specific recommendations regarding screening include using either disposable or reusable probes, screening only after 24 hours of age, and measuring oxygen saturation in both the right hand (pre-ductal) and either foot (post-ductal). A screen is considered positive when 1) any oxygen saturation measured is <90%; 2) oxygen saturation is <95% in both extremities on three measures each separated by one hour; or 3) there is a >3% absolute difference in oxygen saturation between the right hand and foot on three measures each separated by one hour. Any screening that is ≥ 95% in either extremity with ≤ 3% absolute difference in oxygen saturation between the upper and lower extremity would be considered a pass and screening would end. Any newborn with a positive screen first requires a comprehensive evaluation for causes of hypoxemia. In the absence of other findings to explain hypoxemia, CCHD needs to be excluded based on a diagnostic echocardiogram.
In summary, the use of routine pulse oximetry screening appears to be an effective tool to diagnose unrecognized CCHD. The recent legislation passed in the state of Texas is a very positive step in helping to identify newborns who may have otherwise unrecognized serious heart defects, and in preventing potentially catastrophic outcomes.
Penn Laird II, M.D.
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