• Lee W Gemma, Gregory M Ward, Mary M Dettmer, Jennifer L Ball, Peter J Leo, Danielle N Doria, and Elizabeth S Kaufman.
• Heart and Vascular Research Center, MetroHealth Campus of Case Western Reserve University, Cleveland, Ohio, USA.
• J. Cardiovasc. Electrophysiol. 2011 Oct 1; 22 (10): 1141-6.

Introductionβ-Blocker therapy reduces syncope and sudden death in long-QT syndrome type 1 (LQT1), but the mechanism of protection is incompletely understood. This study tested the hypothesis that β-blockade reduces QT prolongation and dispersion of repolarization, measured as the T peak-to-end interval (T(pe) ), during exercise and recovery in LQT1 patients.Methods And ResultsQT and T(pe) were measured in 10 LQT1 patients (33 ± 13 years) and 35 normal subjects (32 ± 12 years) during exercise tests on and off β-blockade. In LQT1 patients, β-blockade reduced QT (391 ± 25 milliseconds vs 375 ± 26 milliseconds, P = 0.04 during exercise; 419 ± 41 milliseconds vs 391 ± 39 milliseconds, P = 0.02 during recovery) and markedly reduced T(pe) (91 ± 26 milliseconds vs 67 ± 19 milliseconds, P = 0.03 during exercise; 103 ± 26 milliseconds vs 78 ± 11 milliseconds, P = 0.02 during recovery). In contrast, in normal subjects, β-blockade had no effect on QT (320 ± 17 milliseconds vs 317 ± 16 milliseconds, P = 0.29 during exercise; 317 ± 13 milliseconds vs 315 ± 14 milliseconds, P = 0.15 during recovery) and mildly reduced T(pe) (69 ± 13 milliseconds vs 61 ± 11 milliseconds, P = 0.01 during exercise; 77 ± 19 milliseconds vs. 68 ± 14 milliseconds, P < 0.001 during recovery).ConclusionIn LQT1 patients, β-blockers reduced QT and T(pe) during exercise and recovery, supporting the theory that β-blocker therapy protects LQT1 patients by reducing dispersion of repolarization during exercise and recovery.© 2011 Wiley Periodicals, Inc.

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