Abstract 2636: Age-Related Triggers for Life-Threatning Arrhythmia in the Genotyped Long QT Syndrome
OBJECTIVES We aimed to examine whether triggers for cardiac events are different depending on the age in genotyped and symptomatic long QT syndrome (LQTS) patients.
BACKGROUND Patients with LQTS become symptomatic in adolescence, but some at age ≥20 y/o. It remains unknown whether clinical features of these symptomatic LQTS patients differ depending on the onset of age.
METHODS Study cohort consisted of consecutive 108 symptomatic LQTS patients (34 males and 74 females from 88 families) who were identified to carry the following genotypes; LQT1 (n = 48), LQT2 (n = 52), LQT3 (n = 8). They were divided into 2 groups according to the age of their first onset of symptoms (low age <20 y/o, n = 75, average age = 10 y/o, and high age ≥20 y/o, n = 33, average age = 43 y/o), and triggers of their cardiac events (ventricular tachycardia, syncope or cardiac arrest) were analyzed. We divided the triggers into 3 categories:
adrenergically-mediated factors; exercise, emotional stress, loud noise and arousal,
vagally-mediated factors; rest/sleep, and
secondary factors; drugs, hypokalemia, and bradycardia.
RESULTS Percentage of patients with family history was significantly higher in the low age group (68% vs. 39%; p = 0.005), and prevalence of females and probands were significantly higher in the high age group (60% vs. 88%; p = 0.004, 75% vs. 97%; p = 0.006, respectively). There were no significant differences in both QTc intervals (523 ± 7 ms vs. 505 ± 10; p = 0.15) and Schwartz scores (6.3 ± 0.2 vs. 5.6 ± 0.3; p = 0.06) between the 2 groups. In the low age group, 76% of the cardiac events were initiated by adrenergically-mediated factors, and 20% were vagally mediated, but none was triggered by secondary factors. In contrast, in the high age group, 48% of the cardiac events were triggered by secondary factors, 12% adrenergically-mediated, and 18% vagally-mediated factors. The prevalence of secondary factors were as follows; 0/75 [0%] in low age vs. 16/33 [48%] in high age; p < 0.001. About the subdivision of secondary triggers on the genotype, hypokalemia was only observed in LQT1, drugs mainly in LQT2, and bradycardia only in LQT2.
CONCLUSION Arrhythmic triggers in LQTS differ depending on the age of the patients, stressing the importance of age-related therapy for genotyped LQTS patients.