1.4f micromanometer tipped catheter

Transthoracic ultrasound cardiography (UCG) was performed using an echocardiographic system (22-MHz linear transducer; LOGIQ e R6 (GE Healthcare, Amersham, UK). Left ventricular end-diastolic and end-systolic diameter (LVDd and LVDs, respectively) were measured in the M-mode at the level of the papillary muscle, and the heart rate was calculated from the RR interval. Fractional shortening (FS) was calculated as FS (%) = 100 × [(LVDd—LVDs)/LVDd]. Hemodynamic analysis was performed using a 1.4-F micromanometer-tipped catheter (Millar Instruments, Houston, TX, USA) as described [22 (link)]. Left ventricular systolic pressure (LVSP) and left ventricular end-diastolic pressure (LVEDP) were measured under light isoflurane anesthesia (0.5%). Measurement of these parameters was performed after intraventricular pressure and HR became stable.

There is a distinct difference in microstructural and biomechanical properties between elastic and muscular arteries (Feng et al., 2021 (link)). There are packaged differences of VSMCs and elastic lamellae between elastic and muscular arteries. The media layer of elastic artery incudes many concentric elastic laminae between internal and external elastic laminae while the muscular artery only has an internal lamina. Moreover, elastic and muscular arteries have different ratios of constitutions, e.g., elastic and collagen fibers and VSMCs. Similar to previous studies (Bing et al., 2020 (link); Li et al., 2021 (link); Wang et al., 2022 (link)), the right elastic CA and right muscular FA were dissected in anesthetized animals before termination at postoperative 3 and 6 weeks. Perivascular flow probes (Transonic Systems Inc.; relative error of ± 2%) were mounted on the two arteries to measure flow waves. A 1.4F micromanometer-tipped catheter (Millar Instruments) was calibrated for zero pressure in 37°C saline and inserted into the two arteries to record pressure waves over 10 cardiac cycles. All data were monitored with a BIOPAC MP150.

Hemodynamic analysis was carried out on rats anaesthetized with 2% isoflurane. A 1.4F micromanometer-tipped catheter (Millar Instruments, Houston, TX, USA) was inserted through the right carotid artery into the LV to record pressure waves in 30 cardiac cycles, which was repeated three times. The zero-pressure baseline of the catheter was calibrated in 37 °C saline. The catheter was monitored with a BIOPAC MP150. LV end-diastolic pressure (EDP), rate of maximum and minimum left ventricular pressure development (dP/dt max, dP/dt min), and time constant of LV relaxation (Tau); artery systolic, Diastolic, and mean pressure (ASP, ADP, AMP) were determined from the measured pressure waves [61 (link)].

LV function was assessed by echocardiography and haemodynamic changes by Millar catheter. After 2 weeks, the animals were anaesthetized, intubated and mechanically ventilated to study haemodynamic variables with a 1.4 F micromanometer-tipped catheter (Millar Instruments). The catheter was inserted into the right carotid artery and advanced into the left ventricle (LV) to measure pressures, which were analysed with the Chart V5 analysis program (Millar Instruments). Echocardiography was performed to measure LV function. Echocardiographic studies were performed with a 15-MHz linear array transducer system (iE33 system; Philips Medical Systems, Andover, MA, USA) by an expert who was not aware of experimental conditions to exclude bias. Two-dimensional guided M-mode of the LV was obtained from the parasternal view. Left ventricle cavity dimension was measured, and percentage change in LV dimension [fractional shortening (FS), LV%FS] was calculated as: LV%FS = [(LVEDD − LVESD)/LVEDE] × 100, where LVEDD is LV end-diastolic diameter and LVESD is LV end-systolic diameter. LV% ejection fraction (EF) was calculated as: LV%EF = [(EDV − ESV)/EDV] × 100, where EDV is LV volume at end-diastole and ESV is LV volume at end-systole. Left ventricle volume was estimated by the area–length method.