Abstract 12824: Higher Prevalence of Qt Interval Prolongation in Infants With Intrauterine Tobacco Smoke Exposure

Abstract

Background: The association between QT interval prolongation and sudden infant death syndrome (SIDS) has been clearly established. Environmental tobacco smoke (ETS) exposure is also associated with increased risk for SIDS. However, there has been little focus on the relationship between the QT interval and ETS exposure during early infancy. To clarify this, we examined the QT interval with ETS exposure during early infancy. Methods: A total of 2168 infants (age:1-4 months), 743 infants who have been exposed to tobacco smoking since intrauterine life and 1425 age-matched children without ETS exposure, underwent electrocardiographic study. QT data were extracted from the electrocardiogram monitor built-in echocardiogram. The QT interval was measured on the first, second, third, and fourth month. The corrected QT interval (QTc) was calculated by dividing the QT interval by the square root of the RR interval (Bazett’s formula). QT interval prolongation was defined as QTc≧440 msec. The data of the number of cigarettes per day were collected by a questionnaire. Results: In the total study population, the mean QTc in ETS infants was significantly greater than in infants without ETS (402±21 and 395±20 msec, p<0.01). The absolute risk of QT prolongation was 1.11 % (16/1425) in infants without ETS; by contrast, that of ETS infants with QTc≧440 msec was 3.23% (24/743) (odds ratio, 2.94; 95% confidence interval, 2.30 to 3.58). The mean QTc in ETS infants at the first, second and third month was significantly greater than that in infants without ETS (404±20 vs. 397±21 msec, 407±19 vs. 399 ±17 msec and 404±17 vs. 390±18 msec, p < 0.01, respectively), but the mean QTc at the fourth month was similar in the 2 groups. The odds ratios for QTc≧440msec in ETS infants at the second and third month were 7.15 (95% confidence interval, 6.00 to 8.29) and 4.97 (95% confidence interval, 2.74 to 7.18), respectively. Compared with infants without ETS, ETS infants with the number of cigarettes ≧10 cigarettes per day had a significantly higher risk of QTc≧440 msec(odds ratio: 3.32, 95% confidence interval: 2.67-3.99). Conclusions: The present study indicates that environmental tobacco exposure is a risk for QT interval prolongation ≧440msec during early infancy.