Objective To study the effects and mechanisms of Poria and Guizhi（Ramulus Cinnamomi） drug-pair on myocardial tissue of rats with chronic heart failure（CHF）. Method A total of 60 male Wistar rats were randomly divided into a sham operation group

a model group

a captopril group and drug-pair high

medium and low dose groups

with 10 rats in each group. Except for the sham operation group

method of constricting the abdominal aorta was used to prepare the model of chronic heart failure（CHF）. After successful modeling

the sham operation group and the model group were given distilled water 2 ml/kg by gavage

and the drug-pair high-dose group was given Poria 2.16 g/（kg·d） and Ramulus Cinnamomi 1.62 g/（kg·d） by gavage; the drug-pair medium-dose group was given Poria 1.08 g/（kg·d）

Ramulus Cinnamomi 0.81 g/（kg·d）; and the drug-pair low-dose group was given Poria 0.54 g/（kg·d） and Ramulus Cinnamomi 0.41 g/（kg·d）; the captopril group was given captopril suspension 6.3 mg/（kg·d） by gavage. All groups were given once a day for 4 weeks. The systolic blood pressure and heart mass index（HMI） of rats in each group were compared. The serum angiotensin Ⅱ（AngⅡ）

tumor necrosis factor α（TNF-α）

interleukin 1β（IL-1β） and endothelin（ET-1） content were detected. HE staining was used to observe the pathological changes of myocardial tissue

and detect the content of angiotensin Ⅱ receptor 1（AT1） in myocardial tissue. Results Compared with the sham operation group

the model group had significantly higher levels of HMI

systolic blood pressure

myocardial tissue AT1

serum AngⅡ

ET-1

TNF-α

and IL-1β（P<0.01）

and pathology showed that the gaps of myocardial cell bundles were slightly widened

and the arrangement of myocardial fibers was disordered

thickened and hypertrophy. Compared with the model group

the levels of HMI

systolic blood pressure

myocardial tissue AT1

and serum AngⅡ

ET-1

TNF-α

and IL-1β in captopril group and drug-pair high-dose groups were significantly reduced（P<0.05 or P<0.01）; the pathology of drug-pair high-dose group and captopril group had reduced myocardial tissue inflammatory cells

clear cell morphology

and low degree of myocardial fibrosis. Compared with the captopril group

there was no statistically significant difference in the drug-pair high-dose group（P>0.05）. Conclusion Drug-pair Poria and Ramulus Cinnamomi could regulate blood pressure in CHF rats

inhibit myocardial hypertrophy and ventricular remodeling

and improve myocardial fibrosis in rats. It may be related to controlling inflammation

and inhibiting neuroendocrine overactivation

and it has best efficacy in high doses.