Key result
Prior symptoms in LQTS linked to a ~12-fold higher rate of breakthrough cardiac events.
Why the study?
Long QT syndrome is a potentially lethal cardiac channelopathy with a 1% to 5% annual risk of syncope, aborted cardiac arrest, or sudden cardiac death, prompting an evaluation of outcomes in the contemporary era.
Cohort (n=606)
No
Although contemporary management of Long QT syndrome results in 92% of patients remaining free of breakthrough cardiac events over a median of 6.7 years, 25% of previously symptomatic patients still experience subsequent nonlethal cardiac events, indicating a need for further treatment optimization.
Specialty-center LQTS management yields low BCE rates; leaves open optimization needs for the 25% of symptomatic patients with subsequent events.
Background Long QT syndrome (LQTS) is a potentially lethal cardiac channelopathy with a 1% to 5% annual risk of LQTS-triggered syncope, aborted cardiac arrest, or sudden cardiac death. Objectives This study sought to evaluate LQTS outcomes from a single center in the contemporary era. Methods The authors conducted a retrospective study comprising the 606 patients with LQTS (LQT1 in 47%, LQT2 in 34%, and LQT3 in 9%) who were evaluated in Mayo Clinic's Genetic Heart Rhythm Clinic from January 1999 to December 2015. Breakthrough cardiac events (BCEs) were defined as LQTS-attributable syncope or seizures, aborted cardiac arrest, appropriate ventricular fibrillation-terminating implantable cardioverter-defibrillator shocks, and sudden cardiac death. Results There were 166 (27%) patients who were symptomatic prior to their first Mayo Clinic evaluation. Median age at first symptom was 12 years. Treatment strategies included no active therapy in 47 (8%) patients, beta-blockers alone in 350 (58%) patients, implantable cardioverter-defibrillators alone in 25 (4%) patients, left cardiac sympathetic denervation alone in 18 (3%) patients, and combination therapy in 166 (27%) patients. Over a median follow-up of 6.7 (IQR: 3.9 to 9.8) years, 556 (92%) patients have not experienced an LQTS-triggered BCE. Only 8 of 440 (2%) previously asymptomatic patients have experienced a single BCE. In contrast, 42 of 166 (25%) previously symptomatic patients have experienced ≥1 BCE. Among the 30 patients with ≥2 BCEs, 2 patients have died and 3 LQT3 patients underwent cardiac transplantation. Conclusions Although outcomes have improved markedly, further optimization of treatment strategies is still needed given that 1 in 4 previously symptomatic patients experienced at least 1 subsequent, albeit nonlethal, LQTS-triggered cardiac event.
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Rohatgi et al. (2017) conducted a cohort in Long QT syndrome (n=606). Previously symptomatic status (under contemporary LQTS management) vs. Previously asymptomatic status was evaluated on Breakthrough cardiac events (LQTS-attributable syncope or seizures, aborted cardiac arrest, appropriate ventricular fibrillation-terminating ICD shocks, and sudden cardiac death). Previously symptomatic LQTS patients had a 25% rate of breakthrough cardiac events vs 2% in asymptomatic patients over 6.7 years, with 92% overall remaining event-free.
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