Abstract 2738: Genotype-Specific Risk Factors for Life-Threatening Cardiac Events during Adolescence in Patients with the Congenital Long QT Syndrome
Background: We hypothesized that risk factors for life-threatening cardiac events in LQTS patients are genotype-specific.
Methods: Cox proportional hazards regression modeling was used to assess risk factors for aborted cardiac arrest (ACA) or sudden cardiac death (SCD) in LQT1 (n=593) and LQT2 (n=427) patients, aged 10 –20 years, from the International LQTS Registry.
Results: The rate of ACA or SCD during adolescence in LQT1 and LQT2 patients is shown in the Figure⇓. Significant risk factors in LQT1 patients included QTc duration (3.5-fold increase in the risk per 10 msec increase in QTc; p=0.01), baseline heart rate (2.1-fold increase in the risk per 100 msec decrease in the RR interval; p=0.03), and prior syncope (3.7-fold increase; p=0.002). By contrast, in LQT2 patients prior syncope was the only significant predictor of ACA or SCD (HR=5.79; p<0.001) during adolescecne, while QTc (HR=1.06 [p=0.13]) and heart rate (HR=1.03 per =100 [p=0.81]) did not contribute significantly to outcome. LQT1 males had a 9.5-fold increase in the risk of ACA or SCD (p=0.04) as compared with the respective females in the age range of 10 –15 year, and exhibited attenuated risk thereafter (HR=0.89; p=0.64), whereas LQT2 males did not have a higher risk than females before- or after- age 15 years (HR=0.46; p=0.50 and HR=0.45; p=0.23, respectively). β-blocker therapy was associated with a respective 70% and 45% reduction in the risk of life-threatening cardiac events in LQT1 and LQT2 patients (p-value for the difference =0.21).
Conclusions: Our findings suggest that risk stratification for life-threatening cardiac events in LQTS adolescents should incorporate genotype-specific risk factors.