Correlation Of Brain Natriuretic Peptide And Cardiac Function Of Rabbits With Hyperthyroid Cardiomyopathy In Different Left Ventricular Geometry

Objective: To explore the correlation of brain natriuretic peptide in the different left ventricular geometry and cardiac function of rabbits with hyperthyroid cardiomyopathy.Methods: Twenty New Zealand purebred rabbits were used in this study,which providedby the Dalian Medical University Experimental Animal Center.Hyperthyroidism model was established by intraperitoneal injection of levothyroxine(45 ?g/kg)for 4 weeks.The success of establishing model is defined upon the appearance of irritation,decreasing body weight and increasing appetite.Totally 18 rats were successfully established.In addition,another ten rats,receiving intraperitoneal injection of 5 mL saline per day,were taken as the control group.conventional echocardiography and quantitative tissue velocity imaging were performed in all the rabbits.Then left ventricular end diastolic diameter(LVDd),interventricular septal thickness diameter(IVSTd),left ventricular posterior wall thickness end diastole(PWTd),were obtained.And calculated relative wall thickness(RWT),left ventricular mass(LVM),left ventricular mass index(LVMI),left ventricular ejection fraction(LVEF)and left ventricular fractional shortening(FS).Mitral annulus systolic and diastolic peak velocity were measured by quantitative tissue velocity imaging.According to the classification of Ganau et al,the 18 hyperthyroidism rabbits were divided into two groups: concentric hypertrophy(n=7)and eccentric hypertrophy(n=11).4 weeks after modeling,evaluated the rabbits plasma BNP,free T3 and free T4.Finally,all rabbits were sacrificed,removed their hearts and observed pathology.Resualts:1.parameters of echocardiographyCompared with control group,each parameters of conventional echocardiography in eccentric hypertrophy rabbits had significant differences except RWT(all P< 0.05).LVDd and LVMI measured in eccentric hypertrophy group were higher than those in concentric hypertrophy group(P <0.01,P< 0.05),while RWT,LVEF,FS were lower(P<0.01).IVSTd,PWTD,RWT,LVMI in concentric group were higher than those in control group(all P< 0.01).LVDd was high normal.But LVEF and FS had no significant differences compared with control group.Compared with control group,the average peak diastolic velocity of mitral ring was significantly lower in concentric hypertrophy and eccentric hypertrophy group(bothP< 0.01),the averagepeak systolic velocity of mitral ring was also lower in the eccentric hypertrophy group(P<0.01).2.the level of plasm BNP and serum FT3,FT4Compared with control group,the level of plasm BNP and serum FT3,FT4 in experimental group were increased obviously(all P< 0.01),and eccentric hypertrophy group was obviously higher than concentric hypertrophy group(P <0.01).3.correlation of plasma BNP and cardiac functionThe level of plasma BNP in experimental group had a positive correlation with LVMI(P <0.05).The peak systolic and diastolic velocity had a negative correlation with plasma BNP(allP< 0.01).4.pathology resultsCompared with control group,concentric hypertrophy and eccentric hypertrophy rabbits' myocardium had varying degrees of damage,and eccentric hypertrophy group had more serious damage than that in concentric hypertrophy group.Conclusion: Experimental findings indicate that,BNP is a sensitive indicator to reflect the cardiac function and myocardial damage in the different left ventricular geometry of rabbits with hyperthyroid cardiomyopathy.