Among patients with border- line-to-normal resting QTc intervals, prolongation of the 4-minute recovery QTc 445 ms had high sensitivity for correctly identifying patients with long QT syndrome.S7.9.1.1-27 A study in younger patients demonstrated QTc prolongation >460 ms at 7 minutes of recovery predicted long QT syndrome type 1 or long QT syndrome type 2 patients versus controls.S7.9.1.1-23 In a study using burst bicycle exercise, patients with latent long QT syndrome had a significantly greater increase in QTc with exercise than either controls or those with QTc prolongation at baseline.S7.9.1.1-24 These findings can be useful in establishing whether long QT syndrome is present. Monitoring ade- quacy of beta-blocker therapy using exercise testing can be beneficial, particularly in school- Beta-blocker ther- apy may be associated with a decrease in supine and peak exercise QTc, with the exception of long QT syndrome type 1 patients with C-loop itive patients with long QT syndrome have QTc intervals 440 ms, most commonly patients with long QT syndrome type 1.S7.9.1.1-31,S7.9.1.1-35 Patients with long QT syndrome and normal QTc have a lower risk of VA and SCD compared to those with prolonged QTc,S7.9.1.1-35 but still have an increased risk of SCA or SCD compared with gen- otype-negative, age- and sex-matched general Beta blockers reduce the risk of adverse cardiac events substantially.S7.9.1.1-1 S7.9.1.1-5, During the periods of highest risk in the first 3 decades of treatment with a beta blocker may reduce risk of SCA.S7.9.1.1-26,S7.9.1.1-28,S7.9.1.1-36, Changes in QTc occur over time, particu- larly during puberty and during and after preg- nancy, indicating the need for assessment of QTc on ECG annually or with medication changes, and assessing medication efficacy with exercise testing as feasible. Asymptomatic adult (male) long QT syndrome patients with normal QTc intervals may choose to decline beta-blocker 7. 