Contemporary Outcomes in Patients With LQTS
What are the contemporary outcomes in patients with long QT syndrome (LQTS)?
This was a retrospective analysis of 606 patients with LQTS who were evaluated at Mayo Clinic. Breakthrough cardiac events (BCEs) were defined as LQTS-attributable syncope/seizures, aborted cardiac arrest, appropriate ventricular fibrillation-terminating implantable cardioverter-defibrillator (ICD) shocks, and sudden cardiac death.
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%), beta-blockers alone in 350 (58%), ICDs alone in 25 (4%), left cardiac sympathetic denervation alone in 18 (3%), and combination therapy in 166 (27%). Over a median follow-up of 6.7 (3.9-9.8) years, 556 (92%) patients have not experienced a 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, two patients have died and three LQT3 patients underwent cardiac transplantation.
Improvement of treatment strategies is needed given that one in four previously symptomatic patients experienced ≥1 LQTS-triggered cardiac event.
LQTS patients followed by this expert center had very low event rates compared with many prior reports. This in large part may be due to the fact that three quarters of the patients had not had antecedent symptoms prior to being seen at the clinic, and that one quarter had concealed (electrocardiographically concealed) LQTS. As such, this cohort represents patients with lesser severity of the disease than in reports from other select centers. Nonetheless, it is also remarkable that treatment with appropriate doses of propranolol and nadolol, in some cases augmented by sympathetic cardiac denervation and/or ICD, has dramatically reduced mortality from LQTS. At 10 years, breakthrough cardiac event-free survival was highest in patients with LQT1 (95%), and lowest in patients with multiple LQT mutations (74%). More work is needed to further risk stratify and improve outcomes in those patients.
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