Assessment Of Cardiac Structure And Function In Patients With Chronic Kidney Disease By Cardiac MR

Chronic kidney disease(CKD)includes all stages of kidney disease,from the earliest stage to end-stage renal disease(ESRD)requiring renal replacement therapy.Epidemiological studies have clearly established a hierarchical association between the severity of CKD and the incidence of cardiovascular events,so that patients with ESRD have the highest cardiovascular risk,which is mainly caused by the non-atherosclerotic progression as cardiac structural and functional abnormalities.Cardiac structural and functional abnormalities in ESRD patients were defined as uremia cardiomyopathy(UC).Recently,the researches have suggested the process of cardiovascular disease had appeared in early-stage CKD with estimated glomerular filtration rate(estimated glomerular filtration rates,e GFR)less than 75ml/min/1.73m~2.So much attention should be paid to abnormalities in cardiac structure and function in patients with early-stage CKD.Particularly after the reversibility of UC after kidney transplantation has been questioned,concerns about the cardiovascular risk of early-stage CKD has been raised.However,little has been known clinically about the features and trends of cardiovascular risk in patients with early-stage CKD.Cardiac magnetic resonance(CMR)can be a comprehensive,non-invasive examination of the heart structure and function,late gadolinium enhancement(LGE)imaging and longitudinal relaxation time(T1 mapping)imaging can intuitively and accurately describe the characteristics of myocardial tissue.Therefore these technologies can be ideally suited to describe the characteristics of cardiovascular risk in patients with CKD and to provide a deep understanding to the pathogenesis of cardiovascular anomalies.This study aimed at the characteristics in early-stage of renal impairment,evolution trend from early-stage to advanced-stage of cardiovascular risk in patients with CKD and the reversibility of UC after renal transplantation,using cardiac cine,native and enhanced T1 mapping and feature tracking technology in CMR.Systematically analysis will contribute to the change of cardiac structure and function in patients with CKD in cross-sectional and longitudinal studies,and the clinical value of CMR parameters will be preliminarily explored.The research contents and results of this paper are as follows:Study of cardiac structure and function in patients with chronic kidney disease at different stages by cardiac MR.A total of 129 patients with CKD from the National Clinical Research Center for Renal Disease of our hospital from July 2015 to April2017 were collected,and 22 healthy volunteers were recruited.CKD patients were staged according to estimated glomerular filtration rate(e GFR):stage 1(e GFR≥90ml/min/1.73m~2),stage 2(e GFR 60-89 ml/min/1.73m~2 with other evidence of nephropathy:proteinuria/hematuria/structural abnormalities/heredity),stage 3(e GFR30-59 ml/min/1.73m~2),stage 4(e GFR 15-29 ml/min/1.73m~2)and stage 5(e GFR<15ml/min/1.73m~2,or with indications of renal replacement therapy).All subjects underwent CMR.CMR acquisition sequences included four-chamber and short-axis cine imaging,short-axis native and enhanced T1 mapping,and short-axis LGE imaging.Analysis parameters included:The left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular end-diastolic mass(LVEDM),left ventricular end systolic mass(LVESM),left ventricular ejection fraction ejection fraction(LVEF),native and contrast myocardial T1 relaxation time,myocardial extracellular volume(ECV)and myocardial strain.Differences in these parameters were compared between healthy volunteers and patients with different stages of CKD.A total of 118 patients with CKD were included in the effective analysis.Subjects were divided into three groups:healthy volunteers,patients with early-middle(stage 1-3)CKD,and patients with advanced(stage 4-5)CKD.LVEDV index,LVESV index,LVEDM index and LVESM index of patients with advanced CKD were significantly higher than those of healthy volunteers and patients with early-middle CKD(P<0.05),and LVEDM index and LVESM index of patients with early-middle CKD were significantly higher than those of healthy volunteers(P<0.05).LVEF in patients with advanced CKD was significantly lower than that in healthy volunteers and patients with early-middle CKD(P<0.05).Native T1 relaxation time at the basal,middle,apical and global level of patients with advanced CKD was significantly higher than that of healthy volunteers and patients with early-middle CKD(P<0.05),and native T1 relaxation time at the basal,middle and global level of patients with early-middle CKD was significantly higher than that of healthy volunteers(P<0.05).Compared with healthy volunteers and patients with early-middle CKD,the middle,apical and overall ECV values in patients with advanced CKD were significantly increased(P<0.05).In patients with advanced CKD,the circumferential strain at the basal and overall level was significantly lower than that in patients with early-middle CKD(P<0.05),and the longitudinal strain was significantly lower than that in healthy volunteers(P<0.05).Increased creatinine,decreased hematocrit,increased renal impairment,elevated height,and a history of cardiac dysfunction were associated with greater left ventricular volume(P<0.05).Reduced e GFR and elevated height were associated with greater left ventricular mass(P<0.05).Elevated serum phosphorus,no smoking history,low age,reduced e GFR and high height were associated with decreased left ventricular systolic function(P<0.05).Decreased hemoglobin or hematocrit,increased creatinine,female,a history of hypertension or cardiac dysfunction,and overweight were all associated with increased degree of diffuse myocardial fibrosis(P<0.05).LVEF was negatively correlated with LVEDV index,LVESV index,basal and global T1 relaxation time(P<0.05),respectively.There was a significant positive correlation between basal circumferencial strain and LVEDV index,LVESV index,LVEDM index,LVESM index and native T1 relaxation time at the basal level(P<0.05),respectively.There was a significant positive correlation between global circumferencial strain and LVESV index,LVEDM index and native T1 relaxation time at the base(P<0.05),respectively.There was a significant positive correlation between longitudinal strain and LVEDV index,LVESV index,LVEDM index and LVESM index(P<0.05),respectively.LVEDV index was positively correlated with native T1 relaxation time and ECV value at the basal,middle,apical,and global level(P<0.05),respectively.There was a significant positive correlation between LVESV index and native T1relaxation time and ECV value at basal,middle,apical and global level(P<0.05),respectively.Conclusions:With the decrease of renal function,left ventricular dilatation,hypertrophy,systolic dysfunction and diffuse myocardial fibrosis are gradually aggravated.There are significant left ventricular dilatation,hypertrophy,systolic dysfunction and diffuse myocardial fibrosis in patients with advanced CKD.In early-middle stage CKD patients,only significant left ventricular hypertrophy and diffuse myocardial fibrosis are observed,at which time the systolic function is slightly compensatory.Both native T1 relaxation time and ECV value are sensitive indicators to evaluate the degree of diffuse myocardial fibrosis in patients with CKD,especially the native T1 relaxation time.The sensitivity in assessment of myocardial systolic dysfunction of longitudinal strain is better than other strain parameters and ejection fraction.Serum phosphorus is one of the risk factors for left ventricular systolic dysfunction in patients with CKD.Degree of anemia,creatinine,and history of hypertension or cardiac dysfunction are all risk factors for diffuse myocardial fibrosis in patients with CKD.Left ventricular systolic function is negatively correlated with left ventricular mass,volume,and diffuse myocardial fibrosis,respectively.Assessment of cardiac structure and function after renal transplantation in patients with end-stage renal disease by cardiac MR.A total of 38 ESRD patients who planned to receive kidney transplantation in the Kidney Transplantation Center of our hospital from September 2015 to January 2018 were collected.All patients received the initial CMR examination 1-2 days before kidney transplantation,and were scheduled to receive follow-up CMR examination at 2 stages(3-4 months,≥6months)after kidney transplantation.CMR acquisition sequences included four-chamber and short-axis cine imaging,short-axis native and enhanced T1mapping,and short-axis LGE imaging.Analysis parameters included:LVEDV,LVESV,LVEDM,LVESM,LVEF,native and enhanced T1 relaxation time,ECV and myocardial strain.The differences of the above parameters before and after kidney transplantation were compared.A total of 25 patients were included in the effective analysis.The enrolled patients had the following characteristics:first,no history of diabetes or ischemic heart disease;second,the duration of dialysis was relatively short,with the median duration of dialysis being 1.7 years;third,the enrolled patients were generally young,with an average age of 27.5 years.LVEDV index(P<0.001),LVESV index(P<0.001)and LVEDM index(P=0.034)of 25 ESRD patients(median time of 7.0 months)were significantly decreased and LVEF(P<0.001)was significantly increased after kidney transplantation compared with those before kidney transplantation.Stage 1 follow-up(median time of 3.5 months):LVEDV index(P<0.001)and LVESV index(P<0.001)were significantly lower than those before kidney transplantation.LVEF(P=0.081)and LVEDM index(P=0.386)were not significantly different from those before kidney transplantation.Stage 2 follow-up(median time of 8.4 months):LVEDV index(P=0.033)and LVESV index(P=0.001)were significantly lower than those before kidney transplantation,LVEF(P=0.007)was significantly higher than that before kidney transplantation,while LVEDM index(P=0.130)was still not significantly different from that before kidney transplantation.The native T1 relaxation time of left ventricle at basal(P=0.001),middle(P=0.001),apical(P<0.001)and global(P<0.001)level of 25 ESRD patients(median 7.0 months)after kidney transplantation was significantly lower than that before kidney transplantation,and the ECV values were not significantly different from those before kidney transplantation(P>0.05).Stage 1 follow-up(median 3.5 months)and stage 2follow-up(median 8.4 months)were similar to above.Except for the global radial strain of the left ventricle(P=0.038)in stage 2 follow-up(median time of 8.4 months),which was significantly higher than that before kidney transplantation,the other strain parameters were not significantly different from those before kidney transplantation(P>0.05).Conclusions:for young ESRD patients without a history of diabetes or ischemic heart disease and with short dialysis time,left ventricular dilatation,left ventricular systolic dysfunction and diffuse myocardial fibrosis in the main abnormalities of UC are reversible after kidney transplantation.It is preliminarily speculated that with the extension of postoperative time,the reversal trends of left ventricular dilatation and diffuse myocardial fibrosis have always existed,while the reversal trend of left ventricular systolic dysfunction is gradually appearing.Native T1 relaxation time can be an ideal index to evaluate the degree of diffuse myocardial fibrosis in ESRD patients.