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The clinical course of patients with 2 relatively common long QT syndrome type 3 mutations has not been well described. In the present study, we investigated the mutational-specific risk in patients with deletional (DeltaKPQ) and missense (D1790G) mutations involving the SCN5A gene. The study population involved 50 patients with the DeltaKPQ mutation and 35 patients with the D1790G mutation. The cumulative probability of a first cardiac event (syncope, aborted cardiac arrest, or long QT syndrome-related sudden death) was evaluated using the Kaplan-Meier method. The Cox proportional hazards survivorship model was used to determine the independent contribution of clinical and genetic factors to the first occurrence of cardiac events from birth through 40 years of age. The Andersen-Gill proportional intensity regression model was used to analyze the factors associated with recurrent syncope. Patients with a DeltaKPQ mutation had a significantly greater probability of a first cardiac event from birth through 40 years of age (34%) than those with the D1790G mutation (20%; p <0.001). Multivariate analysis demonstrated an increased risk of cardiac events among DeltaKPQ carriers compared to D1790G carriers (hazard ratio 2.42, p <0.0001) after adjustment for gender and QTc duration. Patients with DeltaKPQ mutations also had an increased risk of recurrent syncope (hazard ratio 5.20, p <0.001). In conclusion, the clinical course of patients with long QT syndrome type with DeltaKPQ mutations was shown to be more virulent than those with D1790G mutations, and this effect was independent of QTc duration. The findings highlight the importance of knowing the specific mutation in risk stratification of patients with long QT syndrome type 3

Objectives: This study was designed to evaluate the clinical and prognostic aspects of long QT syndrome (LQTS)-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 QT interval corrected for heart rate (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 electrocardiogram recorded in the first year of life included QTc ≥500 ms, heart rate ≤100 beats/min, and female sex. An ACA before age 1 year was associated with a hazard ratio of 23.4 (p < 0.01) for ACA or SCD during ages 1 to 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 might not be effective in preventing fatal or near-fatal cardiac events in this small but high-risk subset

Objectives: This study was designed to evaluate the clinical and prognostic aspects of long QT syndrome (LQTS)-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 QT interval corrected for heart rate (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 electrocardiogram recorded in the first year of life included QTc ≥500 ms, heart rate ≤100 beats/min, and female sex. An ACA before age 1 year was associated with a hazard ratio of 23.4 (p < 0.01) for ACA or SCD during ages 1 to 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 might not be effective in preventing fatal or near-fatal cardiac events in this small but high-risk subset