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orthostatic position may be helpful for the diagnosis of LQTS.232,939 Epinephrine challenge is not recommended as a routine diagnostic tool, as reproducibility is modest.137 Patients with a clinical diagnosis of LQTS are recommended to undergo genetic counselling and testing in specialized centres to receive genotype-specific management and permit identification of relatives at risk. Relatives with a mutation but without QT prolongation still receive a diagnosis of LQTS, as they are at risk of experiencing VA, although less frequently than phenotype-positive patients.940 All LQTS patients receive advice on avoidance of hypokalaemia, QT-prolonging medications and genotype-specific triggers.941–943 Beta-blockers are also recommended in all LQTS patients. Non-selective beta-blockers nadolol and propranolol have greater efficacy in reducing arrhythmic risk.940,944–946

Clinical, electrocardiographic and genetic parameters should be considered for the individual risk estimation.82 Recently, risk stratification based on QT interval duration and genotype has been integrated in a LQTS calculator (the 1-2-3 LQTS Risk calculator).947 The utility of genetic testing is exemplified by the need to avoid genotype-specific risks and by the use of mexiletine as a genotypespecific treatment for LQT3, which reduces the length of QT interval and the number of arrhythmic events.948 It should be noted that different mutations in SCN5A show different responses to mexiletine. For example, selected mutations identified in patients not responding to mexiletine showed a distinctive electrophysiological profile

Telemetry tracings – short-coupled PVC inducing VF

ECG sinus rhythm – short-coupled PVCs

Figure 28 Idiopathic ventricular fibrillation triggered by short-coupled premature ventricular complexes. ECG, electrocardiogram; PVC, premature ventricular complex; VF, ventricular fibrillation. Downloaded from academic.oup.com/eurheartj/article/43/40/3997/6675633 by guest on 07 October 2026