high school athlete due to unrecognized heart disease occurs in roughly 1:200,000 per year.10 Overall, the sudden death of a young athlete (up to the age of 39 years) during exercise occurs less than 100 times each year in the United States11. Although an association has been suggested between the use of stimulant medications and sudden death in children, the available literature suggests that this occurs less than ten times per year in the United States12-14 (Table 2). Based in part on a small number of adverse effects reported in Canada, recommendations to consider ECG screening of children taking stimulant medications were made by the AHA and AAP in 2008.15 In de-Wahl Granelli’s study4 there were 5 deaths due to unrecognized congenital heart disease in the 108,604 babies in the control arm and no deaths in the 38,429 babies in the population in which pulse oximetry screening was performed. Although not designed to test the hypothesis, her study suggests that the implementation of pulse oximetry screening decreases the risk of death due to a missed diagnosis of critical congenital heart disease. No such population based data exists for the implementation of screening strategies to decrease the incidence of death in athletes or those taking stimulant medications. Detection of Congenital Heart Disease and the Cyanotic Blind Spot Traditionally, congenital heart disease is detected prenatally with obstetric ultrasound or postnatally by physical examination or the development of symptoms. The prenatal diagnosis of congenital heart disease is the preferred mechanism, but data from both the US and UK suggests that most children with critical congenital heart disease are not detected prior to birth.16-17 Physical examination of the newborn is the oldest method for detecting congenital heart disease prior to symptoms and remains invaluable, but has significant limitations. Certain types of critical ductal-dependent congenital heart disease will not be detected, even by experienced clinicians in the first days after birth. In the setting of valvar atresia or single ventricle physiology with systemic pulmonary pressures, there may not be a heart murmur to alert the clinician to the presence of heart disease. With a large PDA supporting the systemic circulation the femoral pulses may well be normal. A major limitation of the newborn physical examination is the inability for the human eye to detect important degrees of cyanosis. The limits of visual recognition of cyanosis are well documented, but are frequently underappreciated. Nearly a century ago, it was suggested that between 4 and 6 grams of deoxygenated hemoglobin per deciliter of blood would be necessary for central cyanosis to be visible18 (Lundsgaard & Van Slyke 1923). Later reports suggested that only 3 grams of deoxygenated hemoglobin would be necessary to manifest central cyanosis19 (Lees 1970). Even if only three grams of deoxygenated hemoglobin need be present for the observation of central cyanosis, this still leaves a wide gap between normal saturation and visible cyanosis, the cyanotic blind spot (Figure 1). In a one day old term baby with a hemoglobin at the 50th percentile (17.5 g/dL),20 cyanosis would be visible at or below approximately 83%. The cyanotic blind spot widens with anemia and in a one day old term baby with a hemoglobin at the 5th percentile (13.5 g/dL),20 cyanosis would not be visible until the saturation had dropped to 78% or below. More recent work by O’Donnell21 suggests that both the ability to visually detect cyanosis and the inter-observer reliability of visual observations of cyanosis are poor even among neonatal intensive care personnel. This study was performed in the delivery room where a rapid increase in oxygen saturation is expected. The threshold for the resolution of cyanosis varied from 10% to 100% between the observers. Although the infants’ hemoglobin concentrations were not reported in this study, the mean threshold saturation for the visible resolution of cyanosis was 69%. Pulse Oximetry Screening to Detect Unrecognized Ductal Dependent Heart Defects The use of pulse oximetry to detect cyanosis in asymptomatic term neonates as a screening for critical congenital heart disease has been studied for several years. The use of pulse oximetry for this purpose has been viewed with scrutiny, as any intervention applied on a large scale should be. Although pulse oximetry could be conNEONATOLOGY TODAY www.NeonatologyToday.net Incidence of Death Due to Unrecognized Heart Disease Cause Estimated Number of Deaths Per Year in US Unrecognized Critical Congenital Heart Disease in Neonates 100-200 Sudden Death of a Young Athlete 24 hours no repeat if abnormal foot ≥ 94% 1:311 for CHD 1% Riede 2010 44240 >24 hours repeat in 1 hour if abnormal foot ≥ 96% 1:1036 for CHD 1:3454 for any disease 26% for CHD 78% for any disease No matter how screening is performed, false positive results will result in increased cost, delay in discharge, and anxiety. However, when echocardiography cannot be performed without transfer to another center the costs, delays, and anxieties associated with false positive studies will increase considerably. The application of pulse oximetry screening to rural settings with limited access to echocardiography may be challenging. In Wisconsin alone, half of the state’s children were born in one of the 98