Refractoriness and conduction interaction during modulation of non-ischemic ventricular fibrillation by flecainide.
OBJECTIVE
To study refractoriness and conduction interaction during modulation of non-ischemic ventricular fibrillation (VF) by flecainide.


METHODS
Isolated feline and rabbit hearts were used. (a) In the feline hearts (n = 8), electrophysiological parameters were measured before and after flecainide administration (0.6, 1.2 x 10(-6) M). During pacing the parameters were: epicardial conduction time, refractoriness and 1:1 pacing/response capture. During 8 min of electrically-induced tachyarrhythmias they included heart rate and normalized entropy reflecting the degree of organization. (b) In rabbit hearts (n = 4), three-dimensional mapping was performed before and after flecainide administration (2 x 10(-6) M). To follow changes in organization, local RR-intervals and differences in activation time between adjacent epicardial electrodes were measured immediately and 80 sec after VF induction.


RESULTS
In feline hearts with flecainide, fibrillation was more difficult to induce, more frequently terminated spontaneously and was slower and more organized; conduction time was markedly lengthened, and refractoriness less than 1:1 capture, was moderately prolonged. An inverse correlation was observed between arrhythmia properties, rate and organization, and changes in refractoriness and conduction time. In rabbit, the number of wave fronts was reduced, RR-intervals were prolonged but at the same time activation time differences between adjacent electrodes were smaller following flecainide administration.


CONCLUSIONS
It is suggested that flecainide modulation of VF properties is associated with conduction suppression and refractoriness prolongation, which act in a synergistic, additive way.
Neufeld Cardiac Research Institute, Tel Aviv University, Israel. giora.amitzur@sheba.health.gov.il
Giora
G
Amitzur
Nitza
N
Shenkar
Matthias
M
Mueller
Patricia
P
Kraft
Ilia
I
Novikov
Michael
M
Eldar
Jonathan
J
Leor
Eugenia
E
Raichlin
Wolfgang
W
Schoels
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002415:Cats; D004562:Electrocardiography; D019277:Entropy; D005424:Flecainide / Q000494:pharmacology*; D005583:Fourier Analysis; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D011817:Rabbits; D014693:Ventricular Fibrillation / Q000503:physiopathology*
D000889:Anti-Arrhythmia Agents; D005424:Flecainide