Clinical presentation and course of long QT syndrome in Thai children

Congenital long QT syndrome (LQTS) is a genetically transmitted cardiac channelopathy that can lead to lethal arrhythmia and sudden cardiac death in healthy young people. The clinical characteristics of LQTS are variable and depend on the subtype of long QT syndrome, which differ among populations. This single hospital-based case review study examined the clinical presentation of long QT syndrome and the outcomes of its treatment in 20 Thai children at King Chulalongkorn Memorial Hospital in Bangkok, Thailand.

Inpatient and outpatient records of children (aged 0-14 years) diagnosed with long QT syndrome from January 1, 1998, to September 30, 2013, were retrospectively reviewed. Presentation at diagnosis, treatments, and clinical courses were collected and analyzed. In the 20 subjects, total Schwartz scores totaled 5.2±0.9 points, and mean age at diagnosis was 7.6±4.4 years (range, 1 day-13.8 years). The patients were assigned to one of 3 groups based on trigger events: 50% of patients had events at rest (sleep or at rest), 35% experienced adrenergic-mediated events (e.g., stress, exercise, startle), and 15% were asymptomatic. Excluding the 3 patients who died at first presentation, 100% of patients received a beta blocker, and 47.1% were treated with an automatic implantable cardioverter-defibrillator (AICD).

At follow-up (median=959 days; range, 1-4170 days), 4 patients (20%) were known to have died, 3 of whom died shortly after the diagnosis. Among patients who survived the initial event, 52.9% (9 of 17) experienced cardiac events (appropriate AICD shock, death, and/or syncope) during the follow-up period. The mean duration from diagnosis to cardiac event was 1420±759 days (range, 497-2499 days).

All 20 patients with LQTS were mostly symptomatic at presentation. Owing to the geographical region and ethnicity of the Thai population, we conclude that the ratio of patients who develop cardiac symptoms at rest or during sleep might be higher than in other Asian countries.