EFFECTS OF 2,3-BUTANEDIONE MONOXIME ON ATRIAL-ATRIOVENTRICULAR NODAL CONDUCTION IN ISOLATED RABBIT HEART

BDM Effects on AVN Conduction. Introduction: 2,3-Butanedione monoxime (BDM) has been found to reversibly block cardiac contraction, without blocking electrical conduction, This study characterizes the dose-depe ndent effects of BDM ore the conduction through the atrioventricular n ode (AVN) of rabbit heart. Methods and Results: Thirteen isolated atri al-AVN preparations were used in control, during and after exposure to 5, 10, and 20 mM BDM. Anterograde and retrograde pacing protocols wer e used to obtain the Wenckebach cycle length, effective and functional refractory periods of the AVN, index of AVN conduction delay (the are a under the AVN conduction curve), as well as index of intra-atrial co nduction delay between the AVN inputs, Compared to control, 5 and 10 m M BDM produced either shortening or net effect on all of the above par ameters except a slight (6% and 14%, respectively) increase in the int ra-atrial delay. At 20 mM, BDM produced a further increase in the intr a-atrial delay (up to 50%) as well as in the retrograde AVN conduction delay (up to 16%), while the characteristics of the anterograde condu ction were still improved, The effects of perfusion with BDM ion these parameters were reversible after washout. Conclusions: Aside from its known effect as an electromechanical uncoupler, BDM reversibly altere d some of the electrical responses of the AVN, Most of these alteratio ns, however, did not impede hut rather improved AVN conduction, Since a dose of 10 mM is sufficient to fully eliminate undesirable motion, B DM should he considered a safe and valuable tool in AVN studies in vit ro requiring a mechanically quiescent preparation.