Effects of flecainide in patients with new SCN5A mutation: mutation-specific therapy for long-QT syndrome?

Circulation. 2000 Apr 11;101(14):1698-706. doi: 10.1161/01.cir.101.14.1698.


Background: Mutations in the cardiac sodium channel gene (SCN5A) can cause one variant of the congenital long-QT syndrome. The effects of some of these mutations on the alpha-subunit channel properties can be blocked by type Ib antiarrhythmic drugs. Recently, we have described a new SCN5A mutation (D1790G) that affects the channel properties in a manner suggesting that sodium blockers of the Ib type will be ineffective in carriers of this mutation. Hence, the ECG effects of flecainide-acetate, a type Ic sodium blocker, were evaluated in carriers of this mutation.

Methods and results: Eight asymptomatic mutation carriers and 5 control subjects were studied. Intravenous lidocaine was tested first in only 2 mutation carriers and had no significant effect on any ECG parameter. Flecainide significantly shortened all heart rate-corrected repolarization duration parameters only in carriers and not in control subjects: QT(c) shortened by 9.5% (from 517+/-45 to 468+/-36 ms, P=0.011), and the S-offset to T-onset interval shortened by 64.7% (from 187+/-88 to 66+/-50 ms, P=0.0092). Flecainide also normalized the marked baseline repolarization dispersion in most mutation carriers. These effects among carriers were maintained during long-term (9 to 17 months) outpatient flecainide therapy with no adverse effects.

Conclusions: This report is the first to describe SCN5A mutation carriers who significantly responded to flecainide therapy yet did not respond to lidocaine. These results have important implications for long-QT allele-specific therapeutic strategies.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anti-Arrhythmia Agents / therapeutic use*
  • Case-Control Studies
  • Electrocardiography
  • Female
  • Flecainide / therapeutic use*
  • Heart / drug effects
  • Heart / physiopathology
  • Heterozygote
  • Humans
  • Injections, Intravenous
  • Lidocaine / therapeutic use
  • Long QT Syndrome / drug therapy*
  • Long QT Syndrome / genetics*
  • Long QT Syndrome / physiopathology
  • Male
  • Mutation*
  • NAV1.5 Voltage-Gated Sodium Channel
  • Pedigree
  • Sodium Channels / genetics*


  • Anti-Arrhythmia Agents
  • NAV1.5 Voltage-Gated Sodium Channel
  • SCN5A protein, human
  • Sodium Channels
  • Lidocaine
  • Flecainide