Prevalence of early-onset atrial fibrillation in congenital long QT syndrome

Background: The prevalence of atrial fibrillation (AF) in the young (age <50 years) is 0.1%, or 1:1,000 persons. Mutations in KCNQ1-, KCNH2-, and KCNA5-encoded potassium channels and SCN5A-encoded sodium channels have been reported in familial AF. A mechanism of atrial torsade has been suggested to occur in patients with congenital long QT syndrome (LQTS). Objective: The purpose of this study was to determine the prevalence of AF in patients with congenital LQTS. Methods: History of documented AF was sought from two independent cohorts. One cohort consisted of 252 consecutive patients (146 females and 106 males, average age at diagnosis 23 ± 16 years, QTc 465 ± 51 ms) with genetically proven LQTS seen at Mayo's LQTS Clinic. The second cohort consisted of 205 consecutive patients (133 females and 72 males, average age at testing 23 ± 16 years, QTc 479 ± 51 ms) with a positive FAMILION genetic test (PGxHealth) for LQTS. Results: Early-onset AF was documented in 8 (1.7%) of 457 patients, including 6 (2.4%) of 252 patients seen at Mayo and 2 (1%) of 205 patients with a positive FAMILION test. Five (2.4%) of 211 patients with LQT1-susceptibility mutations had documented AF, compared to 0 of 174 patients with LQT2, 1 of 59 patients with LQT3, 1 of 1 patient with Andersen-Tawil syndrome, and 1 of 34 patients with multiple mutations. The average age at diagnosis of AF of the six patients evaluated at Mayo was 24.3 years (range 4-46 years). Early-onset AF (age <50 years) was significantly more common in patients with LQTS compared to population-based prevalence statistics (P <.001, relative risk 17.5). Conclusion: Compared to the background prevalence of 0.1%, early-onset AF was observed in almost 2% of patients with genetically proven LQTS and should be viewed as an uncommon but possible LQT-related dysrhythmia. Clinical complaints of palpitations warrant thorough assessment in patients with LQTS.