Reference Intervals for ECG Parameters in Anesthetized Guinea Pigs

Introduction. Guinea pigs (Cavia porcellus) are widely used as the standard test systems in preclinical studies. Although electrocardiographic (ECG) parameters are acknowledged to be highly significant in drug safety assessment, and similarity between the cardiovascular anatomy of guinea pigs and humans is deemed evident, the data regarding reference values of ECG parameters corresponding to various anesthesia protocols are rather scarce in the present-day scientific literature. The aim of the study is to obtain the up-to-date reference intervals for ECG parameters in anesthetized guinea pigs to standardize the usage thereof in preclinical studies. Materials and Methods. The study was conducted at JSC “Research-and-Manufacturing Company “Home of Pharmacy” in 100 guinea pigs (50 males and 50 females) aged 6–7 months, in the period from 2024 to 2025. ECG recordings were obtained using a “Poly-Spectrum” computer-based electrocardiograph, from the animals in the dorsal recumbent position, subjected to general anesthesia (with a combination of tiletamine/zolazepam in a dose of 8 mg/kg and xylazine in a dose of 2 mg/kg). The reference intervals (RIs) and 90% confidence intervals were calculated using the robust method (the outliers being excluded prior to calculation), and the Box-Cox transformation technique. Results. The reference intervals were established for heart rate (HR); for RR, P, PQ, QRS, and QT intervals; and for the amplitudes of P, Q, R, S, and T waves. Mean HR values under anesthesia were found to range from 150 to 230 bpm. Statistically significant sex-based differences in HR, the duration of RR, QRS, and QT intervals, and R-wave amplitude were identified. Normal background changes such as P- and T-wave inversion were also described for this species, those observed in 6–26% of clinically healthy animals. Discussion and Conclusion. The obtained data are consistent with the inhalation anesthesia parameters reported in the literature but are significantly different from the parameters observed in awake animals, which confirms the need of using the reference intervals specific to the particular experiment settings. The obtained results made it possible to standardize the way of functional state assessment of the guinea pigs’ cardiovascular system, thereby enhanced the data interpretation reliability of preclinical studies and their translational value.