Differential effects of quinidine and flecainide on plateau duration of human atrial action potential.
Quinidine and flecainide, two class-I antiarrhythmics increase action potential duration (APD) at 90% repolarization and cellular refractory period in human atrial fibers without significant change in resting potential. On the other hand, quinidine decreases APD at 50%, whereas flecainide slightly increases, which suggests different effects on Ca2+ current. Using isolation cell procedure and whole cell recording, we found that 10 microM quinidine (34.77 +/- 6.5%, n = 5) and 0.5 microM flecainide (50.46 +/- 6.2%, n = 4) decrease calcium current in human atrium. It is concluded that, at therapeutical concentrations, quinidine and flecainide modify the action potential plateau phase in a different manner, which is not only related to the calcium current decrease.
Hatem
S
S
U 256 INSERM, Instrumentation et dynamique cardiovasculaire, Hôpital Broussais, Paris, France.
Le Grand
B
B
Le Heuzey
J Y
JY
Couétil
J P
JP
Deroubaix
E
E
D000200:Action Potentials / Q000187:drug effects; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000503:physiopathology; D016275:Atrial Function; D002118:Calcium / Q000378:metabolism; D005424:Flecainide / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006325:Heart Atria / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D011802:Quinidine / Q000494:pharmacology*
D011802:Quinidine; D005424:Flecainide; D002118:Calcium