Tr50b

Telemetry was conducted on the rats in protocol 2 after the MI surgery. We placed a radiotelemetry transmitter (TR50B; AD Instruments, Sydney, Australia) body in the abdominal cavity of the rats; the positive lead wire was placed on the xiphoid process, while the negative lead wire was placed between the sternocleidomastoid muscles. The frequency domains were very‐low‐frequency (VLF; 0.05 Hz), low‐frequency (LF; 0.05‐0.75 Hz), and high‐frequency (HF; 0.75‐2.5 Hz) bands. Data from dynamic electrocardiography (ECG) was recorded via the LabChart Pro software (AD Instruments). The ratio of LF to HF was calculated. The ECG was monitored for 24 hours until the RSNA recording.

A telemetry electrocardiograph transmitter (TR50B; ADInstrument) was positioned in the abdominal cavity of rats of as previously described.²¹ Two leads were placed on the dorsal surface of the xiphoid process and into the anterior mediastinum, close to the right atrium. Twenty‐four‐hour dynamic electrocardiography was performed, and the electrocardiogram (ECG) data were continually recorded by a PowerLab physiology system and analysed using LabChart Pro software (ADInstruments). A 15 min ECG recording was selected to analyse HRV. Low‐frequency (LF; 0.05–0.75 Hz) and high‐frequency (HF; 0.75–2.5 Hz) bands were recorded, and the ratio of LF to HF bands was calculated. Telemetric recordings were conducted for 3 days before the devices were removed. After the rats were anaesthetized, cardiac function was measured by echocardiography machine (Fujifilm Vevo 3100). The left ventricular ejection fraction (EF%) and fractional shortening (FS%) were calculated using the M‐mode recording of the parasternal long‐axis view.