Swine as an in vivo model for electrophysiologic evaluation of cardiac pacing parameters

Pre-clinical studies of cardiac pacemakers and new electrodes, materials, and designs are for the most part conducted in dogs. Dogs, however, have electrophysiological differences which may preclude accurate translation to clinical trials. The purpose of this study was to develop normal electrophysiological parameters for an animal whose cardiovascular system more closely resembles that of man than any nonprimate animal. The threshold (voltage and current) strength-duration curves of the pig showed the same inverse relationship between the pulse duration and threshold requirements as other species. At 0.5 ms the atrium had 3.5-5.5 times greater energy requirements, over twice the current (2.04 mA vs 0.72 mA) and twice the voltage (0.75 mV vs 0.32 mV) requirements when compared to the ventricles. The pig's S-A nodal P-wave was superior in amplitude (7.80 +/- 1.80 mV vs 4.28 +/- 2.27 mV) and the slew rate was faster (1.30 +/- 0.56 mV/ms vs 0.44 +/- 0.50 mV/ms) compared to that of the atrial appendage. The pig's left ventricular myocardial R-wave had significantly greater amplitude (19.00 +/- 6.44 mV vs 10.70 +/- 4.34 mV) and faster slew rate (1.60 +/- 0.62 mV/ms vs 0.90 +/- 0.30 mV/ms) compared to the right ventricular endocardial R-wave. The electrophysiological parameters of the pig were more similar to those of man than the dog; therefore, the pig is a useful animal model for electrophysiological studies and the testing of pacemaker equipment.