Abstract
Cardiac intracellular Ca2+ ion (Cai) is generally expressed after membrane potential (Vm) depolarization. However it was reported recently that Cai behave independently from membrane potential during ventricular tachycardia or fibrillation. On behalf of clear the mechanisms of transition between VT to VF, we developed Vm/Cai dual optical mapping system which using 2 high-speed video camera and high precision pixel registration image processing. Voltage sensitive dye was RH237 and Cai indicator was Rhod-2. VT were induced by cross-filed stimulation in isolated rabbit heart specimen. The optical signals were measured by 250fps, 512x512 pixel, 10bit grayscale. Using this system, we captured characteristic phenomenon called “Ca2+ spatial alternans” that Cai cyclic signal amplitude were gradually increased in sustained VT and then the spatial heterogeneity of Cai were accelerated. So we suggest the mechanisms that Ca2+ spatial alternans easily brought wave-breakup of cardiac excitation and finally VT became VF.
