IDENTIFYING INFANTS AT RISK FOR PROLONGED BRADYCARDIA.

Alfred Steinschneider, MD, PhD, Aaron Curns, MPH, Heidi Shoemake, MPH
American SIDS Institute, 2480 Windy Hill Road, Suite 380, Marietta, GA 30067 USA
Phone:770-612-1030. Fax: 770-612-8277. Email: prevent@SIDS.org

A retrospective study was conducted on 447 infants referred to the Institute for home monitoring. Within this study group there were 193 siblings of SIDS victims, 30 with other family history of SIDS, 172 ALTE infants, 46 siblings of an ALTE infant, and 6 infants referred because of parental anxiety. All infants were followed at home on documented apnea/bradycardia monitors and all underwent a nap/feeding study in an environmentally controlled laboratory setting. The objective of our retrospective study was to evaluate the combination of epidemiologic and physiologic variables in identifying infants at risk for prolonged bradycardia. Prolonged bradycardia was defined for this study as a heart rate less than 80 bpm*, in association with respiratory activity, for at least 15 seconds in duration.

A classification tree was formulated using variables that best discriminated between infants that had at least one episode of bradycardia from those that remained episode free. When following the classification criteria of the tree the following results were obtained.

Results of classification.

The risk for bradycardia in infants identified as high risk was 13.3% compared to 0.9% for infants identified as low risk. Other test measures of effectiveness were sensitivity=80.0%, specificity = 81.8%, test (+)= 20.3%, RR=15.7, 95% CI (4.5, 54.4), p<0.0001. The results indicate that one might be able to discriminate between high and low risk infants for prolonged bradycardia by relying on epidemiologic and physiologic information gathered prior to home monitoring.

*Reduced in increments of 10 bpm if alarms were due to respiratory sinus arrhythmia.

**4 infants were not classified due to missing information.

In the spring of 1998, at the 5^th SIDS International Conference in Rouen, France, the American SIDS Institute presented the results from a study complementary in design to the paper described above. In this particular study, researchers used a combination of epidemiologic and physiologic variables to define an infant's risk for pathologic central apnea. To learn more about what was presented by the Institute in France, click on the link below.