Establishment of methodology for non-invasive electrocardiographic measurements in turtles and tortoises.

The lack of knowledge on how to perform species-specific electrocardiographic (ECG) measurements in chelonians makes ECG evaluations difficult. The aim of this study was to establish non-invasive methods for ECG sample collection in different species of non-anaesthetised chelonians, focusing on adhesive and clamp electrodes. A total of 72 turtles and tortoises from 20 species and various sizes were used for the study. Body weight ranged from 32 g to 65 kg. From the aspect of specimen fixation, dorsal recumbency proved to be the most useful. Both adhesive and clamp electrodes yielded results when applied to the plastron and skin folds. Pre-emptive results suggest an indirect correlation with plastron thickness, the presence of a hinge, habitat and measurable ECG wave amplitude. ECG wave recordings are more likely in aquatic chelonians and species with a hinge. With size the plastron also thickens, making wave detection impossible. ECG waves were detected in 41 of the 72 specimens, complete PQRST complexes in 19 animals, with the rest showing absent P waves in all leads. ECG amplitudes were below 1 mV, with an average of 0.15 mV R wave amplitude.