The Experimental Study Of Echocardiography Evaluation The Left Atrial Structure And Function Of Different Left Ventricular Geometry In New Zealand Rabbits With Chronic Intermittent Hypoxia

Objective:To observe the left atrial structure and function of different left ventricular geometry in New Zealand Rabbits with chronic intermittent hypoxia by echocardiography.Methods:The New Zealand white rabbits were placed in the chronic intermittent hypoxia(CIH)chamber and exposed to hypoxia for 8 weeks(6 hours/day, 6 days/week). The flow of nitrogen and oxygen were regulated into the customized chambers by the gas control delivery system. The fraction of inspired oxygen was changed from 21% to 8%. Left ventricular and left atrial structure and function were assessed by echocardiography at CIH0,1,2,4,6,8 weeks.First,We determine the rabbits’ critical value of the left ventricular mass index and the relative wall thickness in CIH 0 week.According the critical value,CIH 8week surviving rabbits were divided into four groups: normal geometry(NG) group,concentric remodeling(CR) set, the concentric hypertrophy(CH) group and the eccentric hypertrophy(EH) group.Then assessed left atrial structure and function of four groups by echocardiography.Finally, histopathology was done by HE staining simultaneously.Results:(1)grouping situation:of 51 New Zealand rabbits at CIH 8 week, there were 16 in normal geometry(NG) group, 20 in concentric remodeling(CR) group, 9 in concentric hypertrophy(CH) group and 6 in eccentric hypertrophy(EH) group.(2)left atrial sttucture:Compared with NG, left atrium maximal volume(LAVmax),left atrium maximal volume/weight(LAVmax/W),left atrium presystolic volume(LAVpre-a) increased in CR(P<0.05);left atrium anteroposterior diameter, left atrium long diameter,LAVmax,LAVmax/W,left atrium minimal volume(LAVmin), LAVpre-a,LAVpre-a/W increased inCH(P<0.05);left atrium anteroposterior diameter, left atrium long diameter, LAVmax,LAVmax/W, LAVmin, LAVmin/W, LAVpre-a, LAVpre-a/W increased in EH(P<0.05);Compared with CR, LAVmax, LAVmin, LAVpre-a increased in CH(P<0.05),LAVmax, LAVmax/W, LAVmin, LAVpre-a increased in EH(P<0.05)(3)left atrial reservoir function:Compared with NG,left atrium total emptying volume(LA Tot EV)increased in CR(P<0.05), LA Tot EV, s wave of pulmonary vein(PVs) increased in CH and EH(P<0.05),Compared with CR, LA Tot EV increased in CH and EH(P<0.05);(4)left atrial conduit function: Compared with NG, left atrial passive emptying volume(LA Pass EV), left atrial passive emptying fraction(LA Pass EF), d wave of pulmonary vein(PVd) decreased in CH and EH(P<0.05), Compared with CR, LA Pass EV,LA Pass EF decreased in CH(P<0.05), LA Pass EV,LA Pass EF, PVd decreased in EH(P<0.05).(5)left atrial booster pump function: Compared with NG,left atrial active emptying volume(LA Act EV) increased in CR(P <0.05), LA Act EV, left atrial active emptying fraction(LA Act EF), a wave of pulmonary vein(PVa) increased in CH and EH(P <0.05); Compared with CR, LA Act EV and LA Act EF increased in CH(P <0.05).Conclusion:Left atrial structure and function varied with left ventricular geometric.In concentric remolding, the function of atrial reservoir and booster pump were increased; In concentric hypertrophy and eccentric hypertrophy, the function of atrial reservoir and booster pump were increased, but the left atrial conduit function was decreased.Then left ventricular filling depended mainly upon the function of left atrial reservoir and booster pump.