Context Data on the efficacy of β-blockers in the 3 most common genetic
long QT syndrome (LQTS) loci are limited.
Objective To describe and assess outcome in a large systematically genotyped population
of β-blocker–treated LQTS patients.
Design, Setting, and Patients Consecutive LQTS-genotyped patients (n = 335) in Italy treated with β-blockers
for an average of 5 years.
Main Outcome Measures Cardiac events (syncope, ventricular tachycardia/torsades de pointes,
cardiac arrest, and sudden cardiac death) while patients received β-blocker
therapy according to genotype.
Results Cardiac events among patients receiving β-blocker therapy occurred
in 19 of 187 (10%) LQT1 patients, 27 of 120 (23%) LQT2 patients, and 9 of 28 (32%) LQT3 patients (P<.001). The risk of cardiac
events was higher among LQT2 (adjusted relative risk,
2.81; 95% confidence interval [CI], 1.50-5.27; P =
.001) and LQT3 (adjusted relative risk, 4.00; 95%
CI, 2.45-8.03; P<.001) patients than among LQT1 patients, suggesting inadequate protection from β-blocker
therapy. Other important predictors of risk were a QT interval corrected for
heart rate that was more than 500 ms in patients receiving therapy (adjusted
relative risk, 2.01; 95% CI, 1.16-3.51; P = .01)
and occurrence of a first cardiac event before the age of 7 years (adjusted
RR, 4.34; 95% CI, 2.35-8.03; P<.001).
Conclusion Among patients with genetic LQTS treated with β-blockers, there
is a high rate of cardiac events, particularly among patients with LQT2 and LQT3 genotypes.