Abstract 10937: What Influences β-Blocker Resistance for Secondary Prevention of Cardiac Events in Patients with Congenital Long QT Syndrome?
[Backgrounds] β-blockers are used as first-line drug to prevent cardiac events (CE; syncope, aborted cardiac death, sudden death) in patients with congenital long QT syndrome (LQTS). It has not been fully elucidated what factor determines β-blocker resistance for CE in patients with congenital LQTS.
[Methods] Study population consisted of consecutively genotyped 254 LQTS patients (94 male, 111 LQT1 and 143 LQT2) who had experienced at least one CE (under 50 years old) before β-blocker therapy. β-blocker resistance was defined as occurrence of CE in the presence of β-blocker therapy. Age at first CE was handled as a consecutive variable in Cox-regression analysis.
[Results] During 7.6 years of follow-up under β-blocker therapy, 52 (20%) of 254 patients [18/111 (16%) LQT1 and 34/143 (24%) LQT2] experienced subsequent CE. β-blocker resistant 52 patients had significantly younger age at first CE, more frequent TdP history, longer QTc interval, higher Schwartz score, and more frequent T wave alternance than β-blocker effective 202 patients (p<0.05). By univariate Cox-regression analysis, younger age at first CE, male gender and transmembrane-pore mutation in LQT1, and younger age at first CE, missense mutation of KCNH2, T wave alternance and notched T wave in LQT2 were risk factors of β-blocker resistance (P<0.05). Multivariate Cox-regression analysis showed that younger age at first CE was an independent risk factor of β-blocker resistance both in LQT1 and LQT2 (HR for a 1-year younger =1.28, P=0.002, HR for a 1-year younger =1.05, P=0.042, respectively).
[Conclusion] Younger age at first cardiac event was an independent risk factor of β-blocker resistance for secondary prevention of cardiac events in both LQT1 and LQT2 patients, suggesting more careful observation was necessary for the patients who exhibited their first cardiac event at lower age.
- © 2011 by American Heart Association, Inc.