Abstract 15060: Carvedilol, an α1- and Non-selective β-adrenoceptor Blocker, for Prevention of Cardiac Events in Patients with Type 2 Long QT Syndrome.
Introduction: β-blocker therapy (BBT) offers first line strategy for treatment of patients with long QT syndrome. Such therapy provides >80% effectiveness in long QT syndrome type 1 (LQT1). In contrast, its efficacy remains as low as ∼59% in LQT2.
Hypothesis: Using patch-clamp techniques, we recently demonstrated that α1-adrenoceptor stimulation by phenylephrine downregulated IKr through the degradation of membrane phosphatidylinositol 4,5-bisphosphate content and α-blockers inhibited this IKr reduction in HL-1 cardiomyocytes. Furthermore, as an anecdotal case, we experienced an LQT2 patient, in whom carvedilol (10mg/day), an α1- and non-selective β-blocker, but not propranolol (30mg/day) suppressed syncope. Accordingly, we assessed the hypothesis that carvedilol could prevent cardiac events more effectively than other β-adrenoceptor blockers in genotyped LQT2 patients.
Methods: The study population consisted of 51 patients that carried KCNH2 mutation (18 males, 23 ± 11 years old) but no additional mutations in KCNQ1 , SCN5A , KCNJ2 or KCNE1–2 . They were divided into 2 groups (group1: 43 patients with selective β-blocker: 51% with propranolol, 10–60 mg/day, and 14 % with atenolol, 25–200 mg/day, group 2: 8 treated with carvedilol, 5–40 mg/day). We retrospectively analyzed and compared the efficacy of respective BBT.
Results: Population characteristics were not different between the two groups. Mean QTc, HR, “Schwartz score” were 513± 62ms vs. 525± 65ms, 64 ± 11 bpm vs. 61± 7 bpm, 5.2± 1.7 vs. 5.6± 1.3 (group1 vs. group2), respectively. There was recurrence of cardiac events in 11 of group1 for 105 ± 90 months (26%) but not in group2 for 62± 47 months (P <0.05, K 2 test).
Conclusions: Carvedilol appeared to be more effective BBT in our LQT2 cohort. A future study is warranted with a larger number of LQT2 patients.
- © 2010 by American Heart Association, Inc.