MRI study of left ventricular remodeling after acute myocardial infarction in rabbit model / 中华放射学杂志

ABSTRACT

ObjectiveTo observe the change of cardiac function after acute myocardial infarction (AMI) in rabbit model,and to study MRI characteristics of left ventricular remodeling (LVR).Methods Forty-five japanese white rabbits underwent chest-opening coronary artery ligation surgery to obtain rabbit myocardial infarction model The animals were scanned on a 1.5 T MR scanner ( GE Healthcare,Chalfont St.Giles,UK) at six time-points as surgery,1,2,4,6,8 weeks after surgery. Cardiac function parameters were measured,including left ventricular end diastolic volume ( EDV ),stroke volume ( SV ),ejection fraction (EF),peak ejection rate ( PER ) and peak firing rate (PFR).At each time point,5 rabbits were randomly selected and performed re-thoracotomy to obtain heart specimen.Each specimen was examined by MRI with the diffusion tensor imaging ( DTI ).The value of ADC and fractional anisotropy (FA) were collected. Cardiac function data sets of different time points were analyzed using repeated measures data of ANOVA.The FA and ADC values of infarction myocardium set of different time points or different parts of the myocardium were analyzed using one-way ANOVA. The average was compared statistically between two adjacent groups using LSD-t test. Results Left ventricular EDV increased in progress with the time.It was increased from ( 2.21 ± 0.35 ) ml preoperatively to ( 3.15 ± 0.57 ) ml 8-week postoperatively.But the difference was not statistical significant ( F =1.384,P =0.220).EF was decreased from(57.31 ± 11.11 )％ to( 34.71 ± 8.72 )％.It dropped significantly and the difference was statistically significant (F =27.134,P =0.001 ).EF showed a downward trend with the increase of EDV.By linear regression analysis,an equation was set up with y =- 5.58x + 57.7 ( F =8.855,P =0.005 ).On the other hand,PER showed a progressive decline from (27.31 ± 13.06) ml/s to ( 17.31 ± 6.41 ) ml/s ( F =2.105,P =0.037 ),and PFR decreased from ( 23.79 ± 14.15 ) ml/s to ( 12.07 ± 6.91 ) ml/s ( F =2.366,P =0.011 ).FA value decreased from 0.442 ±0.093 to 0.107 ±0.037( F =12.61,P =0.001 ),and ADC valueshowed upward trend from (5.07 ± 1.15) ×10-4 mm2/s to(6.39 ±0.78) ×10-4 mm2/s (F=4.166,P =0.022 ).FA values of infarct,adjacent and remote region were 0.201 ± 0.049,0.316 ± 0.127 and 0.323 ± 0.117 respectively( F =3.896,P =0.004 ),and the ADC values in these regions were (6.19 ± 1.78 ) ×10 -4,(5.44 ± 2.63 ) × 1 0 -4,(5.29 ± 2.02 ) × 10 -4 mm2/s respectively ( F =3.248,P =0.018 ).FA and ADC values were significantly different between the infarct region and adjacent region ( t =7.327,P =0.001 ;t =3.292,P =0.005,respectively),but there was no significantly different between adjacent region and remote region ( t =1.024,P =0.129 ; t =1.467,P =0.164,respectively ).ConclusionsMRI measurement of parameters of cardiac function can be used to monitor the process of left ventricular function remodeling after AMI.The process of micro-structural remodeling of myocardium can be reflected by DTI.MRI provides a feasible imaging modality for LVR after AMI.