Background. The purpose of this study was to determine whether polarized arrest using adenosine/lidocaine cold crystalloid cardioplegia in combination with the hibernation inductor delta-opioid receptor agonist pentazocine would give satisfactory myocardial protection rather than using depolarized supranormal potassium cardioplegia, supranormal potassium cardioplegia with pentazocine, or adenosine/lidocaine cardioplegia. Methods. Twenty pigs were randomly divided into four groups (n = 5 each) to receive the four types of cold crystalloid cardioplegia with an aortic cross-clamp time of 1 hour. Hemodynamic data were continuously measured, as was the left ventricular end-diastolic pressure (LVEDP), left ventricular end-systolic pressure (LVESP), plus or minus derivative of change in diastolic pressure over time (+/- dp/dt), cardiac output, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac troponin I, and left ventricular ultrastructure. Results. Both the adenosine/lidocaine/pentazocine group and the adenosine/lidocaine group got significantly better results than the hyperkalemic and hyperkalemic pentazocine groups in improving hemodynamic values, pulmonary capillary wedge pressure, LVEDP, LVESP, +/- dp/dt, cardiac output, cardiac troponin I values, and left ventricular ultrastructure. There were no statistical differences between the adenosine/lidocaine/pentazocine group and the adenosine/lidocaine group at 1 hour after cross-clamp removal; but at 2 hours after crossclamp removal, the adenosine/lidocaine/pentazocine group stands out (LVEDP 3.3 +/- 0.5, LVESP 122.5 +/- 18.9, +dp/dt 2.9 +/- 0.1, -dp/dt 2.0 +/- 0.6, cardiac output 2.6 +/- 0.4, and troponin I 4.9 +/- 0.5), with significant differences from the adenosine/lidocaine group (LVEDP 5.8 +/- 1.0, LVESP 98.5 +/- 10.1, +dp/dt 2.5 +/- 0.2, -dp/dt 1.0 +/- 0.2, cardiac output 2.2 +/- 0.2, troponin I 8.2 +/- 0.8; p < 0.05). The defibrillation rate was largely decreased after the cross-clamp was released in the group containing pentazocine in cardioplegia. Conclusions. Adenosine/lidocaine/pentazocine cold crystalloid cardioplegia gave satisfactory cardiac arrest and better myocardial protection than the other three groups, especially with regard to improving prolonged postoperative cardiac function.