The four groups of rats were placed in a room with a 12:12-hour light and dark cycle and were randomly fed a standard diet and water. The SHR-H, SHR-L, and SHR-C groups received daily intravastric administration of Qili Qiangxin (Qiliqiangxin buy) or excipients for 12 weeks. At the 12th week of treatment, all rats were weighed and their blood pressure was measured once by intra aortic catheter invasion. At the end of the 12-week treatment period, an echocardiogram was performed on each rat. After humanely killing the mice, all the hearts were carefully removed. The middle section of the left ventricle (LV) was immediately divided into 2mm thick cross-sections and immersed in 10% neutral buffer paraformaldehyde for histological analysis. Other tissue samples were quickly frozen in liquid nitrogen and stored at −70°C until analysis was performed. All experimental protocols were approved by the Institutional Animal Care and Use Committee of Harbin Medical University and were in line with the National Institutes of Health guidelines for the use of laboratory animals.

Echocardiography assessed cardiac structure and function. Transthoracic echocardiography was performed using the HP Sonos 2500 equipped with a 7.5-MHz transducer. A 2-D guided M-mode image at a depth of 2 mm was recorded at the tip of the papillary muscle. The posterior and anterior wall thickness of the left ventricle and its diameter during systole and diastole were measured in a short-axis view. All parameters were measured over ≥3 consecutive cardiac cycles. Ejection fraction is defined as follows: Ejection fraction = ((LVEDV - LVESV) /LVEDV×100), where LVEDV is left ventricular end-diastolic volume and LVESV is left ventricular end-systolic volume. Shortening fraction = ((LVEDD -- LVESD) /LVEDD×100), where left ventricular ejection diameter (LVEDD) is left ventricular end-diastolic diameter, and LVESD is left ventricular end-systolic diameter. Cardiac output is derived as follows: Cardiac output = ((ESV-EDV) ×HR), where ESV is end-systolic volume, EDV is end-diastolic volume, and HR is heart rate.