PO-01-144 ACTION POTENTIAL ALTERNANS THRIVE IN CALCIUM BUFFERED VENTRICULAR MYOCYTES

Action potential (AP) alternans (AP-ALT) are linked to increased arrhythmogenesis. It is suggested that calcium (Ca2+) transient (CaT) the primary cause of AP through a bi-directional coupling feedback mechanism because CaT may develop in free conditions. Supporting this notion date, counterpart scenario which absence has not yet been demonstrated. With objective developing experimental model, we revisited idea inducing presence Ca2+ buffer BAPTA and investigated if Bay K 8644, an L-type channel agonist known promoter alternans, was effective buffered cells. We analyzed AP-ALT incidence (positive when sequences 14 or more APs exhibited repetitive short-to-long changes duration (APD)) isolated rabbit ventricle myocytes paced at progressively shorter cycles lengths (CL) from 1000 ms shortest CL > 179 eliciting determine threshold (ALT-TH). perfused Tyrode (37 oC) alone with 25 nM k 8644 upon freely contracting loaded (via patch microelectrode) 10 20 mM completely abolish CaT. developed abundantly (AP-ALT 65 vs 80 91%, Controls BAPTA, respectively). had similar ALT-TH (226±37 269±88 ms, p>0.05) magnitude (13±5 17±9 p>0.05), but both parameters were larger (273±56 21±13 respectively magnitude, p<0.05). Concomitantly, ALT-TH, diastolic interval (DI) all groups (46±17 46±18 49±10 Control whilst APD (180±34 223±73 ms), significantly (225±52 p<0.02 Controls). Delivery elicited prolongation followed by crescendo (APD beat-to-beat increasing amplitude leading loss 1:1 capture) 11/11 (CL=300 ms) 6/6 (CL=1000 ms). In thrive sensitive activation rate and/or drugs promoting alternans. Therapies aiming reduce its dynamic response should consider this.