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. 2009 Nov 3;120(18):1761-7.
doi: 10.1161/CIRCULATIONAHA.109.863209. Epub 2009 Oct 19.

Prevalence of the congenital long-QT syndrome

Peter J Schwartz  1 , Marco Stramba-Badiale, Lia Crotti, Matteo Pedrazzini, Alessandra Besana, Giuliano Bosi, Fulvio Gabbarini, Karine Goulene, Roberto Insolia, Savina Mannarino, Fabio Mosca, Luigi Nespoli, Alessandro Rimini, Enrico Rosati, Patrizia Salice, Carla Spazzolini
Affiliations

Prevalence of the congenital long-QT syndrome

Peter J Schwartz et al. Circulation. .

Abstract

Background: The prevalence of genetic arrhythmogenic diseases is unknown. For the long-QT syndrome (LQTS), figures ranging from 1:20 000 to 1:5000 were published, but none was based on actual data. Our objective was to define the prevalence of LQTS.

Methods and results: In 18 maternity hospitals, an ECG was performed in 44 596 infants 15 to 25 days old (43 080 whites). In infants with a corrected QT interval (QTc) >450 ms, the ECG was repeated within 1 to 2 weeks. Genetic analysis, by screening 7 LQTS genes, was performed in 28 of 31 (90%) and in 14 of 28 infants (50%) with, respectively, a QTc >470 ms or between 461 and 470 ms. A QTc of 451 to 460, 461 to 470, and >470 ms was observed in 177 (0.41%), 28 (0.06%), and 31 infants (0.07%). Among genotyped infants, disease-causing mutations were found in 12 of 28 (43%) with a QTc >470 ms and in 4 of 14 (29%) with a QTc of 461 to 470 ms. One genotype-negative infant (QTc 482 ms) was diagnosed as affected by LQTS on clinical grounds. Among family members of genotype-positive infants, 51% were found to carry disease-causing mutations. In total, 17 of 43 080 white infants were affected by LQTS, demonstrating a prevalence of at least 1:2534 apparently healthy live births (95% confidence interval, 1:1583 to 1:4350).

Conclusions: This study provides the first data-based estimate of the prevalence of LQTS among whites. On the basis of the nongenotyped infants with QTc between 451 and 470 ms, we advance the hypothesis that this prevalence might be close to 1:2000. ECG-guided molecular screening can identify most infants affected by LQTS and unmask affected relatives, thus allowing effective preventive measures.

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Figures

Figure 1
Figure 1
Distribution of the 43,080 Caucasian neonates among 5 subgroups (absolute numbers and percentage), according to QTc duration on the screening ECG. Neonates positive at the genetic analysis are also reported.
Figure 2
Figure 2
A) ECG tracing of a neonate with a markedly prolonged QT interval. Genetic analysis identified a mutation on KCNH2 (LQT2). B) ECG tracing of the neonate's father. Genetic analysis identified the same mutation on KCNH2 (LQT2).
See this image and copyright information in PMC

Comment in

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