Experimental cardiac tachyarrhythmias in guinea pigs.

Despite years of intense research into the mechanisms of defibrillation, there remain many unanswered questions. In many fields, hypotheses are first tested in rodent models before confirming the results in larger animals. This work suggests the guinea pig as a rodent model for defibrillation. Twenty-eight guinea pigs were studied, all male retired breeders weighing over 900 g. T-wave stimuli (upper limit of vulnerability [ULV]) were given after 15 rapid pacing beats, since the rapid pacing has been suggested to extend the tachyarrhythmia. Defibrillation (DF) was attempted after 5 seconds. The correlation between the ULV50 and DF50 in guinea pigs (0.82, n = 8) is very close to that seen in dogs (0.85). Also, the sensitivity of the DF50 to waveform is similar (476 +/- 176 for monophasic vs 364 +/- 94 V for biphasic P < 0.005, n = 10). The dose-response curve widths (2.3 +/- 1.7 for ULV vs 1.9 +/- 1.8 for defibrillation, n = 10) show the same trend of increasing curve widths for ULV, and similar magnitude to dogs (mean 1.8). We rarely (<1.5%) observed spontaneous conversion in less than 10 seconds. The guinea pig can be used as a model for defibrillation as it shows many of the same characteristics as dogs.