Abstract
BackgroundBeta-blockers are first-line therapy in patients with congenital long-QT syndrome (LQTS).ObjectiveThis study sought to determine the differences in effectiveness of beta-blockers on risk reduction according to LQTS genotype.MethodsWe searched MEDLINE, EMBASE, and CENTRAL databases to investigate the use of beta-blockers (atenolol, nadolol, propranolol, and metoprolol) in patients with LQTS. Hazard ratio (HR) and relative risk (RR) were extracted or calculated from studies reporting cardiac events (syncope, aborted cardiac arrest (ACA), or sudden cardiac death (SCD)).ResultsAmong 2,113 articles searched, 10 studies (7 registry-based cohort studies (Cohort) and 3 interrupted time series studies (ITS)) involving 9,727 patients were included. In a meta-analysis using a random-effect model, the use of beta-blocker was associated with significant risk reduction of all cardiac events (HR 0.49, p<0.001 in Cohort; RR 0.39, p<0.001 in ITS) and serious cardiac events (ACA or SCD) (HR 0.47, p<0.001 in Cohort). In both LQT1 and LQT2, the risk was reduced with beta-blocker therapy in Cohort (HR 0.59 in LQT1; HR 0.39 in LQT2) as well as ITS (RR 0.29 in LQT1; RR 0.48 in LQT2). Among the beta-blockers, nadolol showed a significant risk reduction in both LQT1 and LQT2 (HR 0.47 and 0.27, respectively), whereas atenolol and propranolol decreased the risk only in LQT1 (HR 0.36 and 0.46, respectively). Metoprolol showed no significant reduction in either genotype. In LQT3, beta-blocker therapy was not as effective as LQT1 or LQT2; however, it was inconclusive due to data insufficiency.ConclusionThis meta-analysis showed that beta-blockers were effective in reducing risk of cardiac events in patients with LQTS. Among them, nadolol was effective in LQT1 and LQT2, whereas other drugs showed different effectiveness depending on LQT genotype.
Highlights
Congenital long-QT syndrome (LQTS) is one of the most common inherited arrhythmia syndromes and was described for the first time in 1957 [1]
In a meta-analysis using a random-effect model, the use of beta-blocker was associated with significant risk reduction of all cardiac events (HR 0.49, p
In both long-QT type 1 (LQT1) and Long-QT syndrome type 2 (LQT2), the risk was reduced with beta-blocker therapy in Cohort (HR 0.59 in LQT1; Hazard ratio (HR) 0.39 in LQT2) as well as ITS (RR 0.29 in LQT1; RR 0.48 in LQT2)
Summary
Congenital long-QT syndrome (LQTS) is one of the most common inherited arrhythmia syndromes and was described for the first time in 1957 [1]. The mechanism of betablockers to prevent cardiac events is generally considered to be related to an anti-adrenergic effect, and their efficacy has been shown in previous studies [5,6,7]. Previous observational data demonstrated differing efficacy among the drugs. These differences could be attributed to LQTS subtype and the specific beta-blocker [8,9,10]. The concept of a genotypephenotype mechanism has been proposed as cardiac events in each subtype of LQTS are associated with gene-specific triggers [11]. Beta-blocker use is considered the most effective in patients harboring LQT1, which is closely related to increased sympathetic tone, whereas the drugs are least effective, even harmful, in patients with LQT3, in which rate-dependent fatal ventricular arrhythmia occurs. Beta-blockers are first-line therapy in patients with congenital long-QT syndrome (LQTS)
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