AIM: β-blockers are first line of treatment in patients with congenital Long QT Syndrome (cLQTS) (class-I or II recommendation) in order to prevent malignant arrhythmias. Hence, we examined long-term β-blocker adherence and associated risk factors among patients with cLQTS.

METHODS AND RESULTS: Danish patients with cLQTS claiming a prescription for any β-blocker after their cLQTS diagnosis were identified using data from nationwide registries and specialized inherited cardiac disease clinics (1995-2017). Patients were followed for up to five years. Treatment breaks >60 days were assessed (i.e. proxy for reduced adherence). Multivariable cox regression was used to identify risk factors associated with >60 days breaks in β-blocker treatment. Overall, 500 out of 633 (79%) patients with cLQTS claimed at least 1 prescription for any β-blocker after cLQTS diagnosis. During follow-up, 38.4% had a treatment break. Risk factors significantly associated with treatment breaks were implantable cardioverter defibrillator (ICD) (hazard ratio [HR] = 1.65, 95%confidence interval [CI]: 1.08-2.53), β-blocker side-effects (HR = 2.69, 95%CI: 1.75-4.13), and psychiatric disease (HR = 1.63, 95%CI: 1.04-2.57). By contrast, patients presenting with ventricular tachycardia/syncope as cLQTS disease manifestation were less likely to have a treatment break compared with asymptomatic patients (HR = 0.55, 95%CI: 0.33-0.82).

CONCLUSION: Reduced β-blocker adherence was common with more than a third of patients having a treatment break >60 days after cLQTS diagnosis. Patients with psychiatric disease, self-reported β-blocker side-effects, and ICD were more likely to display reduced adherence whereas a severe cLQTS disease manifestation was associated with optimal β-blocker adherence.