Electrophysiological Effects Of Shenmai Injection On Ischemia Myocard In Rabbit

Cardiac arrhythmia refers to abnormal variation of origin of exciting, rate and rhythm and conduction velocity and conduction sequence of heart. Various organic heart diseases are the most common causes of arrhythmia, and among those diseases, ischemic heart disease, heart failure and cardiogenic shock, are more likely to cause serious cardiac arrhythmias. Arrhythmia can be caused by pathological changes of sinoatrial node, ventricular papillary muscle and outflow tract. Studies have shown that left ventricular outflow tract (aortic vestibule) not only is the output path of the blood, but also has autorhythmic cells in specific areas, belonging to the slow response cells, The autorhythmic slow response action potentials are recorded from the left ventricular outflow tract of guinea pigs, rabbits and rats.Shenmai injection originated from ancient prescription Shenmai Yin. It is commonly used in clinical Chinese medicine preparations. It mainly used in the treatment of both qi and Yin deficiency type of shock, coronary heart disease, viral myocarditis and other diseases. Clinical studies and animal experiments have confirmed that Shenmai injection is very useful for the treatment of various cardiac arrhythmias. But its direct effects on ischemic myocardium are unknown. Therefore, the purpose of this study is to find the electrophysiological effects of Shenmai injection on ischemic myocardial of ventricular papillary muscle, sinoatrial node and the left ventricular outflow of rabbit.In the present study, glass microelectrode technique was applied to observe potential changes in vitro heart. Firstly, myocardial cells were perfused with normal perfusion solution, then with the simulated ischemia perfusion solution, finally Shenmai injection was added. Computer continuous recording method was adapted and the potential changes were simultaneously observed. Measured potential parameters at5,10,15,20min were measured. Six indicators of Ventricular papillary muscle cells, such as resting potential (RP) and amplitude of action potential(APA), duration of50%repolarization of action potential (APD50), duration of90%repolarization of action potential(APD90), duration of action potential(APD) and maximal rate of depolarization of phase0(Vmax) were measured. Seven indicators of pacemaker cells of sinoatrial node and autorhythmic slow response cells of left ventricular outflow tract, such as APA, APD50, APD90, Vmax, maximal diastolic potential (MDP), velocity of diastolic depolarization of phase4(VDD) and rate of pacemaker firing(RPF) were measured. Last, data was analyzed with statistical software.The results of the experiment were as follows:when ventricular papillary muscle was perfused with ischemia perfusion solution, APD50, APD90, APD, Vmax and APA were significantly decreased. Compared with control group (P<0.05or P<0.01), RP did not change significantly. With the Shenmai injection perfusion added, APD50, APD90and APD extended obviously (P<0.05or P<0.01).Shenmai injection had no significant effect on RP, Vmax and APA (P>0.05). When Pacemaker cells of sinoatrial node were perfused with ischemia perfusion solution, APD50and APD90prolong significantly (P<0.05or P<0.01), Vmax significantly reduced (P<0.05), VDD and RPF significantly decrease (P<0.01), the absolute value of MDP and APA reduced, but the change was not obvious (P>0.05). When Shenmai injection was added, Vmax, VDD and RPF has quickened significantly (P<0.05or P<0.01), APD50and APD90became significantly shorter (P<0.05or P<0.01), MDP and APA increased after the treatment, but they were no significant changes (P>0.05). Autorhythmic slow response cells of left ventricular outflow tract were perfused with ischemia perfusion solution, APD50and APD90increased significantly (P<0.05or P<0.01), Vmax declined significantly (P<0.05), VDD and RPF significantly decrease (P<0.05or P<0.01), although the absolute value of MDP and APA reduced, but the change was not obvious (P>0.05). When Shenmai injection was added, VDD and RPF quickened significantly (P<0.05or P<0.01), APD50and APD90significantly reduced (P<0.05). Although Vmax, MDP and APA inscreased, but there was no statistical difference (P>0.05).Based on the above results, it can be concluded that with the simulated ischemia perfusion solution, the electrophysiological properties of ventricular muscle cells, P cells of sinoatrial node and autorhythmic slow response cells of left ventricular outflow tract changed dramatically. Based on these changes, it can be speculated that ischemia hypoxia decreases conductivity of ventricular muscles, autorhythmicity and conductivity of autorhythmic cells. Shenmai injection can obviously affect the electrophysiological changes of myocardial cells.