Late-Breaking Clinical Trials Abstracts

BACKGROUND International guidelines advise universal beta- blocker therapy as either a class I (symptomatic or QTc > 470 ms) or class II (asymptomatic and QTc < 470 ms) recommendation for treatment of long QT syndrome (LQTS). OBJECTIVE The purpose of this study was to evaluate the outcomes of a highly selected cohort of patients with LQTS managed with an observation -only (intentional nontreatment) strategy. METHODS The cohort was derived from a comprehensive retrospec- tive registry of patients with LQTS. Clinical phenotype and genotype data were collected via review of electronic health records. RESULTS Among 661 patients with LQTS, 55 (8.3%) asymptomatic patients (53% female; 16 age < 18 years) were managed with inten- tional nontherapy. Only preventative measures were advised. Mean age at diagnosis was 37.8 +/- 21.2 years. Mean QTc was 448 +/- 30 ms. None of the patients experienced an LQTS-triggered cardiac event over mean follow-up of 7.5 +/- 4.3 years. Compared to the largertreated cohort, this intentionally untreated cohort was less symp- tomatic, was older at diagnosis, and had lower resting QTc values ( P < .0001). CONCLUSION After careful clinical evaluation, risk assessment, and institution of precautionary measures, an observation -only strategy may be considered in a highly selected group of LQTS patients with a clinical pro fi le that includes asymptomatic status, older age at diagnosis, and QTc < 470 ms, with excellent outcomes and better quality of life than LQTS patients treated with beta- blocker. LQTS patients with this low -risk pro fi le should not receive a prophylactic implantable cardioverter -de fi brillator.