Effects of high thoracic epidural blockade on myocardial myosin heavy chain expression in rats with heart failure

Objective To investigate the effects of high thoracic epidural blockade (HTEB) on myocardial myosin heavy chain (MHC) expression in the rats with heart failure. Methods Twenty-eight male Wistar rats, weighing 200-250 g, were randomly divided into 4 groups (n = 7 each): control group (group C), heart failure group (group HF), HTEB group and normal saline group (group NS). Heart failure was induced by subcutaneous injection of isoprenaline 340 mg/kg once a day for 2 days. After 8 weeks, a microspinal catheter was inserted into die epidural space from T3 or T4 level to T1 level in group NS and HTEB. In group NS and HTEB, 0.9% normal saline 50 μl and 0.15% ropivacaine 50 μl were injected through the microspinal catheter every 4 h in the daytime for 30 d respectively. Left ventricular eml-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) were measured 8 weeks after injection of isoprenaline (T1) and 30 d after epidural administration (T2). Pathological results of myocardial and lung tissues were observed, the expression of α-MHC mRNA and β-MHC mRNA was measured by RT-PCR and the percentage of mRNA coding for α-MHC and β-MHC in total MHC mRNA was calculated at T2. Results Compared with group C, LVEDD was increased, LVEF decreased, α-MHC mRNA expression down-regulated while β-MHC mRNA expression up-regulated, and the ratio of α-MHC mRNA to MHC mRNA decreased while the ratio of β-MHC mRNA to MHC mRNA increased in the other 3 groups (P 0.05). LVEF in group HTEB was significantly higher at T2 than at T1 (P 0.05). Pathological changes in myocardial and lung tissues in group HTEB were milder at T2 than at T1. Conclusion HTEB can improve cardiac function by correcting abnormal expression ratio of α-MHC to β-MHC in rats with heart failure. Key words: Anesthesia, epidural; Heart failure, congestive; Cardiac myosins