Asthma and the risk of cardiac events among patients with long QT syndrome after age 40

Background: Limited data exist on the impact of asthma on long QT syndrome (LQTS) in middle-aged and older adults. Objective: This study aimed to examine the association between asthma, β2-agonist treatment, and cardiac events (CEs) in LQTS patients over 40 years of age. Methods: The risk of CEs (comprising syncope, aborted cardiac arrest, implantable cardioverter-defibrillator shock, or sudden cardiac death) from age 40 through 75 years, by the presence of asthma with and without treatment with a β2-agonist inhaler, was assessed among 1020 LQTS patients from the Rochester LQTS Registry. Results: Among 1020 LQTS patients, 162 (16%) had asthma by age 40 years or subsequent follow-up, with 63% treated with a β2-agonist inhaler. Patients with asthma vs no asthma had a higher cumulative rate of CEs from age 40 through 75 years (44% vs 26%, P < .001). Consistently, multivariate analysis showed that asthma was associated with a 2-fold (hazard ratio 1.97, P = .001) increased risk of CEs. Subgroup analysis showed that the association of asthma with CEs was consistent within risk subsets of LQTS patients, including QTc duration, syncope prior to age 40 years, β-blocker use, sex, and LQTS genotype (all P values for risk subset-by-asthma interaction >.10). Asthma patients with LQTS who were treated with a β2-agonist inhaler did not show an increased risk compared with those who were not treated (hazard ratio 1.02, P = .963). Conclusion: The presence of asthma is associated with increased risk of CEs among middle-aged and older patients with LQTS regardless of baseline risk factors or treatment with a β2-agonist inhaler.