Objectives This study was designed to evaluate the clinical and prognostic aspects of long QT syndrome-related cardiac events that occur in the first year of life (infancy). Background The clinical implications for patients with long QT syndrome who experience cardiac events in infancy have not been studied previously. Methods The study population of 3,323 patients with QTc ≥ 450 ms enrolled in the International LQTS Registry involved 20 patients with sudden cardiac death (SCD), 16 patients with aborted cardiac arrest (ACA), 34 patients with syncope, and 3,253 patients who were asymptomatic during the first year of life. Results The risk factors for a cardiac event among 212 patients who had an ECG recorded in the first year of life included QTc≥500ms, heart rate ≤100bpm, and female sex. ACA before age 1 year was associated with a hazard ratio of 23.4 (p<0.01) for ACA or SCD during age 1-10 years. During the 10-year follow-up after infancy, beta-blocker therapy was associated with a significant reduction in ACA/SCD only in those with a syncopal episode within 2 years before ACA/SCD, but not for those who survived ACA in infancy. Conclusions Patients with LQTS who experience ACA during the first year of life are at very high-risk for subsequent ACA or death during their next 10 years of life, and beta-blockers may not be effective in preventing fatal or near fatal cardiac events in this small but high-risk subset.

Background We evaluated the risk factors and clinical course of Long QT syndrome (LQTS) in African-American patients. Methods The study involved 41 African-Americans and 3,456 Caucasians with a QTc ≥ 450 ms from the U.S. portion of the International LQTS Registry. Data included information about the medical history and clinical course of the LQTS patients with end points relating to the occurrence of syncope, aborted cardiac arrest, or LQTS- related sudden cardiac death from birth through age 40 years. The statistical analyses involved Kaplan-Meier time to event graphs and Cox regression models for multivariable risk factor evaluation. Results The QTc was 29ms longer in African-Americans than Caucasians. Multivarite Cox analyses with adjustment for decade of birth revealed that the cardiac event rate was similar in African-Americans and Caucasians with LQTS and that β-blockers were equally effective in reducing cardiac events in the two racial groups. Conclusions The clinical course of LQTS in African-Americans is similar to that of Caucasians with comparable risk factors and benefit from β-blocker therapy in the two racial groups.

Diabetes mellitus can affect ventricular repolarization, and we investigated the impact of diabetes on the risk for cardiac events in older patients with Long QT Syndrome (LQTS). The study population consisted of 1,152 patients with QTc≥450ms who were enrolled in the U.S. portion of the International LQTS Registry and survived beyond 40 years of age. Patients were categorized as having diabetes if they received oral diabetic medication or insulin. End points after age 40 included first cardiac event (syncope, aborted cardiac arrest, sudden cardiac death, whichever occurred first) and all-cause mortality. Follow-up extended from age 41 to 75 years. The risk factors for the end points were evaluated by the Cox model. During follow-up, 193 patients experienced a first cardiac event, and 99 patients died. Among LQTS patients, the development of diabetes in adult LQTS patients was not associated with an increased risk of first cardiac events dominated by syncope. The risk factors for mortality were syncope before age 41, QTc ≥500ms, heart rate >80bpm, and diabetes; there was no mortality interaction involving diabetes and QTc ≥500ms. In conclusion, diabetes and prolonged QTc contributed independent mortality risks in adult patients with LQTS, with no interaction between these two risk factors.While many prior Long QT Syndrome (LQTS) studies have focused on pediatric and young adult patients with this disorder,1 -6 a few recent studies have highlighted the association of LQTS with common co-morbidities in adults >40 years of age.7 , 8 No study, however, has focused on the risk conferred by diabetes mellitus (DM) in LQTS patients despite the fact that QTc prolongation occurs in diabetic patients and contributes to increased risk in patients with DM. 9 The current study examines whether the development of DM is associated with an increased risk for cardiac events in older adults with LQTS. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptAm J Cardiol. Author manuscript; available in PMC 2011 January 1. METHODSWe studied patients >40 years of age who were enrolled in the U.S. portion of the International Long QT Syndrome Registry. Baseline clinical data were obtained on all enrolled family members <41 years of age, and this included ECGs and history of LQTS-related syncope as previously reported. 1 Patient selection criteria for this study required survival >40 years of age in LQTS Registry subjects who had an ECG with QTc ≥450ms and answered a prospective follow-up questionnaire regarding the age of non-LQTS related comorbidities related...

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