Analyses of triggers for recurrent cardiac events in 38 patients with symptomatic long QT syndrome

Objective: To evaluate the main triggers of recurrent cardiac events in patients with symptomatic congenital long QT syndrome (cLQTS). Methods: In this retrospective case analysis study, clinical characteristics were reviewed from 38 patients with recurrent cardiac events after first visit out of 66 symptomatic cLQTS patients. General clinical data such as gender, age, clinical presentation, family history and treatment were collected, auxiliary examination results such as electrocardiogram and gene detection were analyzed. LQTS-related cardiac events were defined as arrhythmogenic syncope, implantable cardioverter defibrillator (ICD) shock, inappropriate ICD shock, aborted cardiac arrest, sudden cardiac death or ventricular tachycardia. Results: A total of 38 patients with recurrent symptoms were enrolled in this study, including 30 females (79%) and 14 children (37%). The average age of onset was (15.6±14.6) years, and the recurrence time was (3.6±3.5) years. Subtype analysis showed that there were 11 cases (29%) of LQT1 (including 2 cases of jervel-Lange Nielson syndrome), 19 cases (50%) of LQT2, 5 cases (13%) of LQT3 and 3 cases (8%) of other rare subtypes (1 LQT5, 1 LQT7 and 1 LQT11) in this patient cohort. LQT1 patients experienced recurrent cardiac event due to drug withdrawal (6 (55%)), specific triggers (exercise and emotional excitement) (4 (36%)) and medication adjustment (1 (9%)). For LQT2 patients, main triggers for cardiac events were drug withdrawal (16 (84%)), specific triggers (shock, sound stimulation, waking up (6 (32%)). One patient (5%) had recurrent syncope after pregnancy. One patient (20%) had inappropriate ICD shock. For LQT3 patients, 4 (80%) patients developed syncope during resting state, and 1 (20%) developed ventricular tachycardia during exercise test. One LQT5 patients experienced syncope and ICD shock under specific triggers (emotional excitement). One LQT11 patient had repeated ICD shocks under specific inducement (fatigue). One LQT7 patient experienced inappropriate ICD shock. Left cardiac sympathetic denervation (LCSD) significantly alleviated the symptoms in 2 children with Jervell-Lange Nielson syndrome (JLNS) post ineffective β-blocker medication. Nadolol succeeded in eliminating cardiac events in one patient with LQT2 post ineffective metoprolol medication. Mexiletine significantly improved symptoms in 2 patients with LQT2 post ineffective β-blocker medication. Conclusions: Medication withdrawal is an important trigger of the recurrence of cardiac events among patients with symptomatic congenital long QT syndrome.