Effectiveness of Pulse Oximetry Screening for Congenital Heart Disease in Asymptomatic Newborns

METHODS

Oximetric screening for critical CCVM was performed by obtaining a single determination of postductal saturation on all asymptomatic newborns (n = 11 281) in the well-infant nurseries of 2 participating hospitals during the study interval. All newborns in the nursery at the time of New York State metabolic screening (hospital A) or all newborns who were being discharged from the well-infant nursery (hospital B) and did not manifest cyanosis, tachypnea (respiratory rate: >60/min), grunting, flaring, retraction, murmur, active precordium, or diminished pulses underwent oximetric screening. Any infant who did manifest any of these clinical findings was transferred to the neonatal intensive care unit for customary evaluation and was not included in the analysis. To ensure universal screening, the timing of the oximetry determination was linked to the state-mandated metabolic screening (>24 hours of age) at hospital A (n = 8642 [76%]). At hospital B (n = 2639 [24%]), screening was performed immediately before discharge as part of the list of discharge procedures (average length of stay for vaginal delivery: 56.9 hours; for cesarean section: 103.2 hours). Critical CCVM was defined as a lesion that would likely require surgical correction during the first month of life. All newborns found to have a postductal saturation ≤95% underwent additional evaluation by echocardiography. Data were collected from May 1998 to November 1999.

RESULTS

Oximetric screening was performed on 11 281 asymptomatic newborns during the study interval: 8642 at hospital A and 2639 at hospital B (Table 2). Three cases of CCVM were detected, including 2 patients with total anomalous pulmonary venous return (oxygen saturation by pulse oximeter: 92%, 88%) and 1 patient with truncus arteriosus (oxygen saturation by pulse oximeter: 86%; Table 3). Therefore, 1 in 3760 asymptomatic newborns was found to have a CCVM by oximetric screening before discharge. There was no accrued cost as reusable oximeter probes were used with oximeters already in place in the nurseries. There was 1 false-positive screen. An asymptomatic infant underwent echocardiography for postductal desaturation and was found to have a structurally normal heart with persistent right to left ductal shunting as a result of delayed transition from the fetal to the neonatal circulation. Two screened infants were readmitted (coarctation, hypoplastic left pulmonary artery with aorto-pulmonary collaterals). Other cardiac diagnoses in the database search were nonurgent, including cases of patent foramen ovale, peripheral pulmonic stenosis, and ventricular septal defect. The prevalence of all cases of critical CCVM in the total population was 1 in 564, whereas in the screened population it was 1 in 2256. Analysis of the screening test’s performance revealed sensitivity of 60%, specificity of 99.95%, positive predictive value of 75%, negative predictive value of 99.98%, and accuracy of 99.97%.

At hospital A, echocardiography was performed on 798 fetuses with expected dates of confinement occurring during the study interval, yielding a diagnosis of CCVM in 15 fetuses with 9 of these being delivered (Tables 2 and 3). Echocardiography performed on 108 fetuses at hospital B detected no major lesions (Table 2). Six infants became symptomatic before screening, and 3 infants who were readmitted from home were born at other hospitals where screening was not performed (Table 3).

DISCUSSION

The discharge physical examination has been shown to be an inadequate screen for CCVM.^6,11,12 An asymptomatic newborn may appear pink despite having clinically significant desaturation. With the incidence of critical CCVM being approximately 2.7 per 1000 live births,¹⁶ we anticipated a higher yield of CCVM case detection by oximetric screening of asymptomatic newborns. The detection rate at hospital B of 1 in 1320 is close to the predicted incidence of 2.7 in 1000 and is comparable to the incidence of congenital hypothyroidism. Despite the large number of prenatally detected lesions, a detection rate by screening of 1 in 3760 for the 2 sites combined is far greater than the rates for most conditions included in the New York State screening program (Table 4).

Comparing the data for the 2 participating institutions reveals the impact of frequently performed fetal echocardiography on the yield from screening (Table 2). Our data suggest that in a center where fetal echocardiography is readily accessible, many lesions will be diagnosed prenatally and therefore will not require screening for detection. This phenomenon has the effect of decreasing the prevalence of CCVM in the population of asymptomatic infants undergoing oximetric screening. Centers where fetal echocardiography is performed less frequently are likely to demonstrate higher yields from oximetric screening.

It is impossible to know whether the newborns with fetal echocardiographic diagnoses in our series would have been detected by screening or would have become symptomatic before screening. However, the prenatally diagnosed lesions in our series, with the possible exception of the case of coarctation, would have been amenable to oximetric detection (Tables 1 and 3). The 2 false-negative screen patients (coarctation, hypoplastic left pulmonary artery with aorto-pulmonary collaterals) had lesions that may not cause desaturation and therefore represent the limitations of screening for CCVM by oximetry (Table 1).

A total of 4 echocardiograms were performed on the basis of postductal desaturation at the time of screening of 11 281 asymptomatic infants. Three of these echocardiograms revealed major CCVM in asymptomatic infants. No unnecessary echocardiograms were performed in the context of this study. Although the fourth echocardiogram did not detect a major CCVM, the infant did have delayed transition from fetal to neonatal circulation with evidence of increased pulmonary artery pressure and right-to-left ductal shunting. This infant remained hospitalized for observation until the pulmonary hypertension resolved.

Oximetric screening for CCVM seems to satisfy the requirements for a screening test: 1) the prevalence of CCVM among asymptomatic newborns is high, particularly in areas with lower rates of fetal echocardiography, 2) the technique of oximetric screening is simple and reliable, 3) effective cardiovascular interventions are available, and 4) the cost/benefit ratio in our series was favorable. No costs were incurred for equipment, supplies, or personnel, and 3 asymptomatic newborns were prevented from going home with undiagnosed CCVM. Oximetric screening for CCVM compares favorably to other newborn screening programs already in place⁹ (Table 5).

The issue of whether detection of critical CCVM by oximetric screening improves the perioperative and long-term outcomes for these infants is beyond the scope of this study. However, studies have shown a favorable impact on outcome with fetal detection of hypoplastic left heart syndrome¹⁷ and transposition of the great arteries¹⁸ compared with neonatal detection. These critical lesions are detectable by oximetric screening (Table 1), and, therefore, it is likely that infants with these lesions detected by screening before discharge from the nursery would also have a better outcome than infants readmitted from home. It is important to note that 10% of the postnatally diagnosed cases in the hypoplastic left heart syndrome study were readmitted from home.¹⁷

Pulse oximetry is already in widespread use in newborn nurseries, and normative data regarding saturation during the period of neonatal cardiopulmonary adaptation has been developed.¹⁹ Oximetry screening is not intended to serve as a substitute for a careful physical examination. Our screening test, based on a single determination of postductal saturation, is noninvasive, cost-effective, and readily coordinated with state-mandated screening tests. The sensitivity, specificity, and predictive value in this population are satisfactory, indicating that screening should be applied to larger populations, particularly where lower rates of fetal detection result in increased CCVM prevalence in asymptomatic newborns. Despite its limitations, implementation of oximetry screening will increase the likelihood that newborns with clinically occult CCVM will be identified in a timely manner.