- ECG =
- electrocardiogram •
- SIDS =
- sudden infant death syndrome
In a recent article that appeared in theNew England Journal of Medicine, Schwartz et al (1998;338:1709–1714) propose that analysis of the QT interval on electrocardiographic (ECG) recordings from infants “may permit the early identification of a substantial percentage of infants at risk for SIDS and the institution of preventive measures.” These conclusions are premature for several reasons: 1) It should be noted that none of the infants who were considered at risk had any recording showing ventricular tachycardia or blocked conduction; thus, in contrast to infants and children who present with near-fatal ventricular tachycardia and then are found to have a prolonged QT interval, none of the infants reported by Schwartz et al had any symptoms that might suggest a potentially fatal rhythm disturbance. 2) The measurements were taken by visual inspection from five nonconsecutive beats, “usually from lead II” making comparison to the reports by others tenuous at best; for example, Southall et al measured the intervals from hundreds of beats in a systematic way by computer. Why do Schwartz et al continue to rely on a method reported more than 75 years ago that relies on visual inspection and, therefore, greater variability than computer-based measures? 3) Schwartz et al don't say that their measurements were performed by cardiologists who were blind to the outcome of the infant; can one safely assume that this method does not introduce bias? 4) If one assumed that the method reported by Schwartz was sufficiently accurate to predict death, one would need to know the sensitivity and specificity of the measurements at various ages. Furthermore, if one used the cut-off between high normal and abnormal at the 97.5 percentile, there would have been about 850 infants from the sample of 34 000 who would be considered at risk. One would then have to evaluate the benefits versus the risks of any therapy recommended for 72 infants, 1 of whom would be expected to die of SIDS.
These reservations strongly suggest that the conclusions reported by Schwartz et al are quite premature, that use of the Bazett method of analyzing the corrected QT interval can't be relied on to prospectively identify infants at risk for SIDS.
- Received October 28, 1998.
- Accepted October 28, 1998.
Reprint requests to (D.C.S.) Pediatric Pulmonary Unit, Massachusetts General Hospital, VBKBA 015, 55 Fruit St, Boston, MA 02114.
- Copyright © 1999 American Academy of Pediatrics