The main cause of arrhythmias is the reentry phenomenon. Spiral wave reentry, a phenomenon of abnormal circulating excitation wave propagation, is speculated to be the cause of ventricular tachycardia (VT) and ventricular fibrillation (VF) . The “spiral wave shift” hypothesis was proposed in a previous simulation study. A spiral wave shift is a phenomenon in which the position of the center of the spiral wave reentry [referred to as phase singularity (PS)] is shifted when electrical stimulation is applied near PS with appropriate position and timing. Since a spiral wave shift can be induced with stimulation energy lower than defibrillation energy, a new defibrillation method has been proposed. This technique involves arbitrarily applying an anatomical block line to collide with PS, thereby stopping VT or VF. However, understanding of the mechanism of a spiral wave shift in biological specimens remains limited. Thus, this study aimed to clarify the mechanism of the spiral wave shift using biological specimens. Spiral wave reentry was induced in perfused rabbit hearts (n=8) stained with a fluorescent dye sensitive to membrane potential. Monophasic stimulation was applied to the surface of each specimen using a multi-electrode array. The timing and position of the electrical stimulation for inducing a spiral wave shift were varied. The optimal conditions for inducing a spiral wave shift were identified as those that minimized the displacement of the PS position after electric stimulation. The results revealed that three conditions must be satisfied to induce a spiral wave shift: (a)the PS and electrode should be located in close proximity to each other, (b)they should be positioned along the cardiac fiber orientation, and (c)electric stimulation should be applied in the repolarization phase of an action potential.
