Association of long QT syndrome loci and cardiac events among patients treated with beta-blockers

Long QT Syndrome (LQTS) is a genetic disease characterized by prolonged ventricular repolarization, syncope, ventricular arrhythmias, and sudden death,1-3 often precipitated by emotion or exercise. Primarily according to nonrandomized trial evidence, beta-blockers are considered first line prophylactic therapy,4 whereas patients refractory to _-blockers may be treated with left-sided cardiac sympathetic denervation, pacemakers, or implantable cardioverter defibrillators.1,5-8 The hypothesis that the efficacy of therapy may vary according to the genetic form of the disease has been proposed7 but not thoroughly investigated. Three genetic loci account for nearly 98% of genetically characterized patients. In this investigation, we sought to describe and assess outcomes of beta-blocker–treated patients affected by the 3 most common genetic loci of LQTS9: LQT1, LQT2, and LQT3, caused by genetic defects on KCNQ1, KCNH2 and SCN5A genes.