AIM: To observe and study the influence of cardiac sympathetic nerve on QT dispersion (QTd) and the circadian variations of QTd in experimental rabbits. METHODS: The rabbits were divided into experimental group (without cardiac sympathetic control by operation) and control group (with retained cardiac sympathetic control by operation, sham operation). QTd of both groups were measured and compared before and after the operation. The circadian variations of QTd were also observed in both groups. RESULTS: QTd in experimental group decreased significantly after the cardiac sympathetic nerves were excised (P

Objective To investigate the effects and relations of carvedilol on heart rate turbulence and secretion of sympathetic nerve in patients with myocardial infarction. Methods Sixty-six patients selected with acute myocardial infarction were randomized to enroll into experimental group ( n = 33 ) treated with earvedilol and control group( n = 33 ) treated with metoprolol for 12 months follow-up treatment. The concenrrarions of plasma norepinephrine(NE) and epinephrine (E) and 24 hour Holter monitoring were messured respectively before the treatment ,after 6 months and 12 months; and new cardiac events were supervised for all cases. Quantification of heart rate turbulenee(HRT) were carried out by computer analyzing two factors: turbulence onset(TO) and turbulence slope(TS) from the data of 24 hour Holter monitoring. NE,E,TO,TS and the occurrence rate of new cardiac events were compared between two groups and in different times of treatment. The correlation between TO,TS and NE,E was analysed. Results Before the treatment, there was no significant differences between two groups to the comparisons of NE,E,TO and TS(P＞0.05). After treating 6 and 12 months, NE, E and TO of experimental group were all lower than control group's significantly, accordingly TS were all higher(P＜0.05). By comparing 3 times( before,after 6 and 12 months of treatment), NE, E and TO of two groups dropped, meanwhile TS rose; experimental group showed significant changes( P＜0.05 ), but control group showed no significant differences(P＞0.05 ). The occurrence rate of new cardiac events of experimental group was lower than control group's significantly (P＜0.05 ).There was significant correlation between NE, E and TO, TS (P＜0.05 ). Conclusion Carvedilol treatment can block the secretion of sympathetic nerve after myocardial infarction and prevent the occurrences of new cardiac events significantly; the changes of the secretion of sympathetic nerve can play an important role for heart rate turbulence (HRT) ,the changes of HRT would be hopeful to predict new cardiac events alter myocardial infarction.

Objective To study the effects of carvedilol on the stability of plasma catecholamine in patients with post-acute myocardial infarction during consecutive periods. Methods Thirty-slx patients selected with acute myocardial infarction were randomized to experimental group treated with the nonselective beta-blocker earvedilol( n=18) and control group treated with the selective beta-blocker metoprolol(=18) for 12-months follow-up. In the two groups,the concentrations of plasma norepinephrine and epinephrine were measured before the treatment and after 2 months,4 months,6 months,8 mouths,10 months and 12 months and new cardiac events were supervised. Results After the treatment, in each point of periods, experimental group showed lower concentrations of plasma norepinephrine and epinephrine statistically than control group(P<0.05) ,and a stable dynamic change during 12 months of treat-ment( P>0.05 ) ;the occurrence rate of new cardiac events was lower significantly in experimental group than in con-trol group(P<0.05). Conclusion Carvedilol can decrease the spillover of sympathetic nerve, control more stably cardiac sympathetic nerve activity and then decrease more sharply the occurrence rate of new cardiac events in pa-tients with acute myocardial infarction than metoprolol.