The response of intact guinea pigs to AC leakage currents

There was a difference in the standard for leakage current in the US and Europe. This difference existed largely because there was very little data on AC stimulation of the heart in situ. In this study, we examine AC stimulation of the in tact guinea pig. Nine male guinea pigs were anesthetized with isoflurane, intubated and monitored with the lead II ECG and optical plethysmograph. For AC stimulation, a stainless steel electrode was used. The return electrode was applied to the right rear paw. Five seconds of AC stimuli at various frequencies was used. The minimum VF threshold in these animals was found to be 558 ± 314 μA at 100 Hz. Frequencies both below (20 Hz: 1584 ± 753 μA) and above (160 Hz: 1355 ± 1007 μA) were found to be significantly different from 100 Hz (20 Hz: p=0.0017 and 100 Hz: p=0.0085). By contrast the minimum current required to have any effect on the heart only increased with frequency from 10 Hz (119 ± 53 μA), to 160 Hz (183 ± 50 μA, p < 0.0001).