Echocardiographic Assessment of Cardiac Function

High-resolution transthoracic echocardiographic measurements were performed using VEVO2100 Ultrasound System for small animals (Fujifilm VisualSonics Inc., Toronto, ON, Canada) using a high-frequency ultrasound probe (MS400) operating at 18–38 MHz. Mice were anesthetised with isoflurane induction: 4.5% isoflurane, 450 mL air and maintenance; 2.0% isoflurane, 200 mL air (Baxter 28 International Inc., Deerfield, IL, USA). LV dimensions and wall thickness were measured from the parasternal short axis M-Mode images using papillary muscles as an indication of mid-ventricular level. LV systolic function was measured by using Teicholz method and diastolic function by measuring the LV relaxation time starting from the peak systole and ending when the maximum relaxation of LV posterior wall was achieved. The analysis was conducted from three consecutive cardiac cycles using VEVO Lab software (Fujifilm VisualSonics Inc., ON, Canada). In addition, ECG signal was acquired via limb electrodes during echocardiography and data were analysed with rodent ECG imaging software (Kubios HRV 2.0, Kuopio, Finland) as previously described [15 (link)].