Contactless magnetocardiographic study of age- and gender-related variability of ventricular repolarization parameters in guinea pigs.

Guinea pigs (GPs) are used for preclinical investigation of the ability of new drugs to induce QT alterations and arrhythmias. The aim of this study was to evaluate the accuracy of multi- site magnetocardiographic mapping (MCG) for the assessment of age-related variation of ventricular 9repolarization (VR) maps in GPs. 18 adult GPs (8 males and 10 females) were investigated with an unshielded 36-channel MCG instrumentation, at the age of 5 months. Only 12 survived until the age of 14 months and were restudied. RR, PR, QRS, QTpeak, QTend, JTpeak, JTend and Tpeak-end intervals were measured from MCG waveforms. Magnetic field (MF) maps and the Equivalent Current Dipole (ECD) inverse solution were automatically computed. At the age of 5 months, average values of VR intervals were slightly longer in males. At the age of 14 months, a statistically significant age-related prolongation of the PR ( pb0.05) and of the QRS ( pb0.01) intervals was found. Neither significant age- nor gender-related variations of VR intervals were appreciable. Statistically significant ( pb0.01) age-related differences were found for the JT α angle, Tpeak α angle and for the distance dynamics. At the same age, the strength of the ECD at the peak of the P, QRS and T waves, was stronger ( pb0.01) than at 5 months. MCG is reliable for VR assessment in GPs. In contrast with findings in rats, age-related changes and gender-related differences of VR parameters were not statistically significant in GPs. More complex variability of MF patterns was observed, which deserves further investigation