Figure 3.

Voltage threshold for irreversible electroporation depends on myocyte orientation with respect to the electric field. Following an intermediate voltage pulse application (140 V, 100 µs), left ventricular myocytes (LVM) oriented parallel or perpendicular to the electric field were exposed to electric pulse (EP) of increasing voltage amplitudes until cell death was observed. A, Representative intracellular Ca²⁺ ([Ca²⁺]_i) traces obtained in a LVM oriented parallel to the electric field show the rise in diastolic Ca²⁺ when incrementing voltage amplitudes. B, Lethal voltage thresholds differed according to cell orientation and with Fura-2. Data are represented as mean±SEr of the mean with individual values for each cell. C, Lethal diastolic Ca²⁺ levels in perpendicular cells were reached at lower voltages than in parallel-oriented cells. Inset: cell orientation and electric field direction. Unpaired t test: ##P<0.01; ###P<0.001. N indicates number of animals; n, number of cells; and r.u., ratio units.