The Effects Of High Thoracic Epidural Anesthesia On Cardiac Function And Expression Of β₃-adrenoceptor In Rats With Heart Failure Induced By Acute Myocardial Infarction

Aim:1. To observe the effect of high thoracic epidural anesthesia (HTEA) on cardiac function and ventricular remodeling in rats with congestive heart failure(CHF) induced by acute myocardial infarction (AMI).2. To investigate the mechanism that HTEA ameliorate cardiac function in a rat model of CHF induced by AMI by examing the expression ofβ3-adenoreceptor (β3AR) and endothelial nitric oxide synthase (eNOS) .Methods:1. 60 rats were randomly divided into LAD group (n=46), in which the anterior descending branches of left coronary artery were ligated, and S group (n=14) underwent sham-operation. Rats were implanted with a PE-10 tuber through atlanto-axial joint in the caudal direction 1 week later. LAD group was randomly divided into HTEA group and CHF group again (n=14/group). 9.0g/L normal sodium 100μL/kg was injected to epidural cavity twice a day separately in S group and CHF group. 1.25g/L bupivacaine 100μL/kg was injected to epidural cavity twice a day in group HTEA. Epidural injection was started 24 hours after the epidural surgery and continued 4 weeks.2. 5 weeks after LAD ligature, the change of cardiac function was observed by measuring left ventricular end diastolic dimension (LVEDd) and left ventricular end systolic dimension (LVEDs), ejection fraction (EF%) and fractional shortening (FS%) by using echocardiogram.3. 5 weeks after LAD ligature, the ratio of heart weight to body weight (HW/BW) and the ratio of left ventricular weight to body weight (LVW/BW) were measured.4. Noninfarct ventricular tissue were stained with hematoxylin-eosin (HE) and Masson's trichrome respectively to observe cardiac myocyte and interstitial collagen fiber.5. Expression ofβ3AR and eNOS mRNA were detected with reverse transcription polymerase chain reaction ( RT-PCR). Expression and localization ofβ3AR were detected with immunohistochemistry in ventricular cardiomyocytes of noninfarct region from 3 groups.Results:1. LVEDd and LVEDs were significantly decreased in THEA rats in comparison with CHF rats (0.76±0.03 vs 0.87±0.07,p<0.01 ;0.55±0.03 vs 0.67±0.06,p<0.01), while EF% and FS% were significantly increased (60±4 vs 50±9,p<0.05 and 28±2 vs 22±5, p<0.01).2. The ratios HW/BW and LVW/BW were significantly increase in the group CHF compared with the group S (p<0.01), but they were limited in the group HTEA (p<0.01).3. Hypertrophy and edema, degeneration and necrosis of myocytes can be seen in rats with CHF, as well as muscle fibers disruption and collagen fiber increase, while the pathological morphous were attenuated in HTEA rats.4. The expression ofβ3AR mRNA were increased significantly in heart failure rats compared with sham-operation rats(1.05±0.02 vs 0.64±0.03,p<0.01). These increases were attenuated after treatment of HTEA (1.05±0.02 vs 0.86±0.02,p <0.01). A similar change was observed for eNOS mRNA(p<0.01).Conclusions:1. Atlanto-axial joint-implanted method can provide a stable and continuous HTEA model in rats.2. HTEA could ameliorate cardiac function in rats with heart failure induced by acute myocardial infarction.3. HTEA could depress pathological change of noninfarct left ventricular myocyte, and prevent hyperplasy of collagen fiber in rats with CHF.4. HTEA could decrease expression ofβ3AR and eNOS mRNA of ventricular myocardium in rats with CHF, and The change could involve mechanism HTEA ameliorate cardiac function and ventricular remodeling.