LCSD is still underutilized because clinicians are often uncertain whether to use it versus an implantable cardioverter defibrillator (ICD). We provide definitive evidence for the long-term efficacy of LCSD in LQTS. The degree of antiarrhythmic protection is influenced by patient's specificity and amount of QTc shortening. This novel approach to the analysis of the outcome allows cardiologists to rationally decide and tailor their management strategies to the individual features of their patients.