Functional ECG Analysis in Mice

Functional testing of the mice’s hearts using ECG was performed as described previously [24 (link)]. The mice were maintained on a 12:12 h dark–light cycle with lights switched on at 6:00 am. All procedures took place during the light phase. Anesthesia was initially induced by placing the mice for 3–5 min in a chamber filled with 3% volume-to-volume isoflurane (Aesica Pharmaceuticals, Hertfordshire, UK). The mice were then positioned on a warm pad (ALA Scientific Instruments, New York, NY, USA) that maintained their temperature during ECG recording. The mice were able to breath freely through a nose cone. Anesthesia was maintained by inhalation of 1.5% isoflurane. Continuous 5-min ECGs were obtained using subcutaneous electrodes attached to the four limbs and recorded via a PowerLab data acquisition system (model ML866, ADInstruments, Colorado Springs, CO, USA) and Animal Bio Amp (model ML136, ADInstruments). The ECG analysis was performed in an unbiased fashion with 1500 beats being analyzed using LabChart 7 Pro version 7.3.1 (ADInstruments). Detection and analysis of QTc interval, QRS intervals, Tpeak-Tend intervals were set to Mouse ECG parameters. The values obtained were compared statistically by the Mann–Whitney U test, and a p < 0.05 was accepted as significant.