Intravenous drug challenge using flecainide and ajmaline in patients with Brugada syndrome.
OBJECTIVE
The purpose of this study was to compare the effect of intravenous flecainide and ajmaline with respect to their ability to induce or accentuate the typical ECG pattern of Brugada syndrome.


BACKGROUND
Brugada syndrome is associated with a high incidence of sudden cardiac death. The typical ECG pattern of ST-segment elevation in the right precordial leads often is concealed, but it can be unmasked with sodium channel blockers such as flecainide and ajmaline. Little is known about the relative effectiveness of these provocative agents in unmasking Brugada syndrome.


METHODS
Intravenous pharmacologic challenge with flecainide and ajmaline was performed. Whole-cell patch clamp techniques were used to assess the relative potency of ajmaline and flecainide to inhibit the transient outward current (I(to)).


RESULTS
A coved-type ST-segment elevation in the right precordial leads was induced or enhanced in 22 of 22 patients following ajmaline administration. Among the 22 patients, only 15 patients showed positive response to flecainide, resulting in a positive concordance of 68%. Both drugs produced equivalent changes in QRS and PQ intervals, suggesting similar effects on sodium channel current. Whole-cell patch clamp experiments revealed a reduction of the total charge provided by I(to) with an IC(50) of 216 and 15.2 microM for ajmaline and flecainide, respectively.


CONCLUSIONS
Our data demonstrate disparate response of Brugada patients to flecainide and ajmaline, with a failure of flecainide in 7 of 22 cases (32%). Greater inhibition of I(to) by flecainide may render it less effective. These observations have important implication for identification of patients at risk for sudden death.
Wolpert
Christian
C
1st Department of Medicine-Cardiology, University Hospital of Mannheim, Faculty of Clinical Medicine of the University of Heidelberg, Germany. christian.wolpert@med.ma.uni-heidelberg.de
Echternach
Constanze
C
Veltmann
Christian
C
Antzelevitch
Charles
C
Thomas
George P
GP
Spehl
Susanne
S
Streitner
Florian
F
Kuschyk
Juergen
J
Schimpf
Rainer
R
Haase
Karl K
KK
Borggrefe
Martin
M
D000404:Ajmaline / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002037:Bundle-Branch Block / Q000175:diagnosis*; D004285:Dogs; D004562:Electrocardiography / Q000187:drug effects*; D005424:Flecainide / Q000494:pharmacology*; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D032383:Myocytes, Cardiac; D018408:Patch-Clamp Techniques; D011446:Prospective Studies; D026941:Sodium Channel Blockers / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; D026941:Sodium Channel Blockers; D000404:Ajmaline; D005424:Flecainide