Abstract: Objective To investigate the characteristics of Na⁺/Ca²⁺ exchanger current (I_Na⁺/Ca²⁺) and K⁺ current remodeling in midmyocardial cells of hypertrophic left ventricle for understanding the ionic basis of arrhythmia of the hypertrophic heart. Methods Twenty New Zealand rabbits were divided equally into normal control group and operation group, and in the latter, left ventricular hypertrophy was induced in the rabbits by partial ligation of the abdominal aorta. Action potentials, I_Na⁺/Ca²⁺, slowly activating delayed rectifier K⁺ current (I_Ks) and rapidly activating delayed rectifier K⁺ current (I_Kr) were recorded in the two groups by using whole-cell patch-clamp technique. Results At the basic cycle length of 2 s, 90% action potential duration (APD₉₀) in control and operation groups was 522.0±19.5 ms (n=6) and 664.7±32.7 ms (n=7) respectively; at the testing potential of +40 mV, outward I_Na⁺/Ca²⁺ density in the two groups was 0.94±0.11 pA/pF (n=9) and 1.30±0.11 pA/pF (n=8) respectively; the testing potential of -100 mV elicited inward I_Na⁺/Ca²⁺ density of 0.40±0.05 pA/pF (n=9) and 0.56±0.02 pA/pF (n=8) respectively. The testing potential of +50 mV induced I_Ks tail current density of 0.26±0.03 pA/pF (n=8) and 0.17±0.01 pA/pF (n=9), and I_Kr tail current density of 0.34±0.02 pA/pF (n=8) and 0.23±0.02 pA/pF (n=9) respectively. Statistically significant differences were identified between the control and operation groups in all the above indices measured. Conclusion The characteristics of electrical remodeling changes in midmyocardial cells of hypertrophic left ventricle, exhibited by prolonged action potential, up-regulated I_Na⁺/Ca²⁺ and down-regulated I_Ks and I_Kr.