Investigation Of Age-related Changes On Left Ventricular Myocardial Systolic Deformation In Spontaneously Hypertensive Rats

Backgrounds and ObjectivesAn accurate assessment of age-related changes on left ventricular contractileproperties in spontaneously hypertensive rats(SHR) is important, which could provide ascientific basis for selecting the appropriate time point in related investigation such as aresearch of heart failure in an animal models. The characteristics of myocardialmulti-dimensional systolic deformation at different weeks of SHR as well as various leftventricular geometry have not been reported previously. This study aimed to investigatemyocardial multi-dimensional systolic deformation at12to82weeks of SHR using2-dimensional strain echocardiography (2DSE) and to explore the age-related changes onleft ventricular contractile properties.MethodsSixty12-week old male SHR were divided into six groups,8-10for each group, tailartery pressure proved to be in hypertension state. They were experimented at12,16,28,45,66and82weeks of age respectively. Echocardiographic examination wasperformed to acquire parameters including LV diameter, wall thickness, left atrial size,LV ejection fraction (LVEF), short-axis fractional shortening（FS）, transmitral diastolicinflow velocities(E, A),and2DSE measurements include endsystolic LV longitudinalstrain (SL), radial strain (SR)，circumferential strain (SC).Invasive parameters includedleft ventricular end-diastolic pressure (LVEDP) and LV±dp/dtmax.Results1. left ventricular wall thickness was gradually increased from28weeks，and it wassignificantly increased at66weeks(p<0.05); left ventricular diameter、LVM、LVMI andleft atrial size were significantly increased from16weeks (p <0.05); There were nosignificant difference in LVEF,and FS from12weeks to66weeks (p>0.05), but at82weeks they were significantly decreased compared to66weeks [(58.26±10.42)%VS (76.84±6.55)%, p<0.05]; at66weeks，E and E/A were significantly lower compared with45weeks (p<0.05).2.2DSE index SC, SR, SL began to increase from16weeks,28weeks reachedhighest (p<0.05), there were no significant difference at45to66weeks of age（p>0.05）,and they were the lowest at82weeks (p<0.05).3. Invasive parameters LVEDP in16weeks and28weeks were lower than12weeks, but45weeks and66weeks were significantly higher than28weeks (p<0.05);LV±dp/dtmax at28weeks were significantly higher than16weeks (p<0.05), but45to82weeks weeks were significantly decreased compared with28weeks(p<0.05).4. Linear correlation analysis shows: LAD and LVMI showed a significant positivecorrelation (r=0.61, p<0.01); When LVMI<17.5g/m~2, significant correlations were foundbetween SC、SR、SL and LVMI (r=0.71,0.67and0.61, p<0.05); when LVMI>17.5g/m~2, theabove strain index was negatively correlated with LVMI (r=-0.74,-0.75and-0.49,p<0.05).Conclusions1. Myocardial systolic deformation changes with aging as well as the progression ofhypertension in SHR. The increases of myocardial systolic deformation with age in theearly stages might suggest a developmental state of myocardial contractile function, andthe hypertensive pathologic decreases of myocardial systolic deformation occurred in thelater stage.2. There was a curve correlation between myocardial systolic deformation and the leftventricular reconstruction, with correlation positively in the early stages and negativelywhen LVMI>17.5g/m~2in the later period.