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(Circulation. 2009;120:1761-1767.)
© 2009 American Heart Association, Inc.

Arrhythmia/Electrophysiology

Prevalence of the Congenital Long-QT Syndrome

Peter J. Schwartz, MD^*; Marco Stramba-Badiale, MD, PhD^*; Lia Crotti, MD, PhD; Matteo Pedrazzini, PhD; Alessandra Besana, PhD; Giuliano Bosi, MD; Fulvio Gabbarini, MD; Karine Goulene, MD, PhD; Roberto Insolia, PhD; Savina Mannarino, MD; Fabio Mosca, MD; Luigi Nespoli, MD; Alessandro Rimini, MD; Enrico Rosati, MD; Patrizia Salice, MD; Carla Spazzolini, DVM, MS

From the Section of Cardiology, Department of Lung, Blood, and Heart, University of Pavia, Pavia, Italy (P.J.S., L.C.); Department of Cardiology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy (P.J.S., L.C., S.M., C.S.); Molecular Cardiology Laboratory, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy (P.J.S., L.C., M.P., R.I.); Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico Italiano, Milan, Italy (P.J.S., A.B.); Department of Medicine, University of Stellenbosch, Stellenbosch, South Africa (P.J.S.); Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research, Department of Medicine, University of Cape Town, Cape Town, South Africa (P.J.S.); Pediatric Arrhythmias Center, IRCCS Istituto Auxologico Italiano, Milan, Italy (M.S.-B., K.G.); Neonatology Unit, Department of Clinical and Experimental Medicine, University of Ferrara, Ferrara, Italy (G.B.); Pediatric Cardiology Division, Regina Margherita Hospital, Turin, Italy (F.G.); Neonatal Intensive Care Unit, Institute of Pediatrics and Neonatology, IRCCS Fondazione Ospedale Policlinico Mangiagalli Regina Elena, University of Milan, Milan, Italy (F.M.); Department of Pediatrics, Del Ponte Hospital, University of Insubria, Varese, Italy (L.N.); Department of Cardiology, IRCCS Istituto G. Gaslini, Genoa, Italy (A.R.); Perinatal Cardiology Unit, Perrino Hospital, Brindisi, Italy (E.R.); and Section of Pediatric Cardiology, Department of Cardiology, IRCCS Fondazione Ospedale Policlinico Mangiagalli Regina Elena, Milan, Italy (P.S.).

Correspondence to Peter J. Schwartz, MD, Department of Cardiology, Fondazione IRCCS Policlinico San Matteo, V. le Golgi, 19, 27100 Pavia, Italy. E-mail peter.schwartz{at}unipv.it

Received March 11, 2009; accepted August 7, 2009.

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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