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 mates, 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 mates, 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-susceptibitity 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-retated dysrhythmia. Clinical complaints of palpitations warrant thorough assessment in patients with LQTS.