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The effects of electric currents applied during absolute refractory period(ARP)on the cardiac function of rabbits with heart failure due to myocardial infarction(MI),and the safety of this method were investigated.Thirty rabbits were randomly assigned equally to 3 groups: sham-operated group,LV-anterior wall cardiac contractility modulation(LV-CCM)group,and septum-CCM(S-CCM)group.A thoracotomy was performed on all the rabbits.Electric pulses were delivered during the ARP on the anterior wall of left ventricle in CCM group and in the septum in S-CCM group,respectively.The left ventricular systolic pressure(LVSP)and maximum positive left ventricular pressure change(+dp/dtmax),heart rates,ventricular tachycardia,ventricular fibrillation were observed.It was found that,as compared with the baseline,LVSP,and+dp/dtmax were significantly increased,on average,by 15.2% and 19.5% in LV-CCM group(P<0.05),and by 8.5% and 10.8% in S-CCM group(P<0.05).LVEDP was significantly decreased and-dp/dtmax increased both in LV-CCM group and S-CCM group(P<0.05).CCM had no effect on heart rate and induced no arrhythmia in short time.It is concluded that electric currents delivered during the ARP could significantly enhance the contractility of myocardium safely,suggesting that CCM stimulation is a novel potent method for contractility modulation.
RESUMO
Objective To investigate the effect of electric stimulation applied during absolute refractory period on contraction and relaxation and Ca 2+ transient of ventricular myocytes from normal guinea-pigs. Methods The ventricular myocytes of guinea-pigs were obtained by enzyme digesting, and the extent of the contraction and relaxation and Ca 2+ transient were recorded through the motion edge detection system. The Ca 2+ transient was reflected by fluorescence ratio (360/380) ( F 360/F 380). Results The ventricular myocytes from the normal guinea-pigs: ①The contraction extent of guinea-pig ventricular myocytes increased by (16.55?5.49)%. The peak velocity of shorting (contraction) and the peak velocity of relengthening (relaxation) increased by (17.43?7.08)% and (19.74?9.08)%, respectively(n=10); ②The extent of F 360/F 380 increased (25.79?6.88)%. The peak velocity of F 360/F 380 increased by (29.47?9.25)% and (22.52?7.81)% during shortening and relengthening, respectively(n=10). The ventricular myocytes from failure guinea-pigs: ①The contraction extent of guinea-pig ventricular myocytes increased by (15.53?5.31)%. The peak velocity of shortening (contraction) and the peak velocity of relengthening (relaxation) increased by (10.60?3.02)% and (23.32?8.26)%, respectively(n=6); ②The extent of F 360/F 380 increased (16.82?7.03)%. The peak velocity of F 360/F 380 increased by (16.27?5.91)% and (10.32?2.46)% during shorenting and relengthening, respectively(n=6). Conclusion Appropriate electric stimulation applied during absolute refractory period might strengthen the contracting and relaxing function of normal and failing ventricular myocytes in guinea-pigs.
RESUMO
AIM: To investigate the influences of electric stimulation applied during the absolute refractory period (ARP) on the cardiac function of normal rabbits and rabbits after myocardial infarction (MI) and to observe the regional effects of this electric stimulation. METHODS: 64 rabbits were randomly assigned to normal and MI groups and each group was then divided into the anterior and posterior groups. A thoracotomy was performed 4 weeks after MI in rabbits. One set of electrodes was inserted into the anterior and posterior wall of left ventricle of the anterior and posterior groups, respectively. Current pulses were delivered during the ARP (called CCM) during sinus rhythm in rabbits. The left ventricular systolic pressure (LVSP) and the left ventricular end diastolic pressure(LVEDP) as well as maximum positive and negative left ventricular pressure change (?dp/dt_(max)) were observed. RESULTS: In the normal and MI groups, LVSP, +dp/dt_(max) significantly increased, and LVEDP, -dp/dt_(max) were reduced during CCM stimulation compared with the baseline (P0.05). CONCLUSION: Electric stimulation delivered during the ARP significantly enhances the contractility and the relaxation of myocardium in normal rabbits and rabbits after MI, and the effects of CCM stimulation on heart are regional. [