Semi-quantification Of Renal Perfusion Using ^99mTc-DTPA In Systolic Heart Failure:A Feasibility Study

The glomerular filtration rate(GFR)is a measure of how well the kidneys are cleaning the blood and excreting waste and extra water.The estimated GFR is the best test to measure the level of renal function and determine the stage of renal disease,if any.It is also a strong predictor of all-cause mortality in ambulatory heart failure(HF).The estimated GFR outperforms left ventricular ejection fraction(LVEF)in this respect.Renal blood flow(RBF)is the effective renal plasma flow through the nephrons per unit time.A reduced RBF is the primary effector mechanism for impaired renal function in HF.Additionally,the glomerular filtration fraction(FF)is another factor that affects GFR.The filtration fraction is the ratio of the GFR to the RBF and helps quantify the proportion of the volume of plasma removed from the dialyzed blood by ultrafiltration,thus giving another measure of how well the kidneys are functioning.Due to the vital role of the kidney in maintaining fluid homeostasis,the human body has developed autoregulatory mechanisms to maintain a stable RBF to contend with various extrarenal disturbances,such as a large drop in cardiac index or arterial pressure.The RBF can remain constant for mean arterial blood pressures as low as 70 mm Hg.Moreover,the GFR can remain unchanged by increasing the FF in the glomerulus when the RBF drops.The GFR declines only if the RBF drops further after the intrinsic autoregulatory capacity is exhausted.However,there is an need to develop a method to detect early subtle changes in RBF,filtration fraction and GFR in HF in clinical practice.Renal perfusion(RP)is a term used to describe blood flow to the kidneys and is commonly assessed with renal scintigraphy;it determines how well blood is delivered to the kidneys and how well the kidneys function.RP very important,it depends on both RBF and venous pressure in HF.Renal scintigraphy with ^99mTc-diethylenetriaminepentaacetic acid(^99mTc-DTPA)is a well-established method for measuring GFR.Importantly,we can semiquantitatively assess RP(GFR,RBF and FF)using the first-pass time-activity curve generated from a region of interest(ROI)over the kidneys.Renal scintigraphy is widely used to assess grafts after renal transplantation.However,there is no report regarding its clinical applications in HF.The goal of this study was to assess the extent of RP dysfunction in patients with systolic HF versus controls using renal scintigraphy with ^99mTc-DTPA.Renal scintigraphy with^99mTc-diethylenetriaminepentaacetic acid(DTPA)may be used to study renal perfusion(RP)in heart failure(HF)patients.The goal of this study was to establish a new method to assess RP in patients with systolic HF.In this retrospective,single-center,observational study,86subjects with left ventricular ejection fraction?45%and 31 age-matched subjects without HF underwent renal scintigraphy with ^99mTc-DTPA.Patients with HF were classified into two categories according to the New York Heart Association(NYHA)functional class,i.e.,moderate HF with NYHA functional class I or II and severe HF with NYHA functional class III or IV.The first-pass time-activity curve of the renal scintigraph was recorded.The GFR was determined by Gates'method.The time to peak perfusion activity(T_p),slope of the perfusion phase(S_p),slope of the washout phase(S_w),and glomerular filtration rate(GFR)in the study were obtained.Differences between groups were assessed by one-way analysis of variance with the Bonferroni post hoc test and rank-sum test.RP in HF was impaired despite comparable GFRs between the control and HF groups.RP in HF was characterized by a longer T_p and a shallower S_pand S_w.The primary parameter(T_p)was significantly prolonged in patients with HF(41.63±12.22s in severe HF vs.26.95±6.26 s in moderate HF vs.17.84±3.17 s in control,P<0.001).At a cutoff point of 22 s,there was a high sensitivity(0.895)and specificity(0.935)in identifying patients with HF.Renal scintigraphy with^99mTc-DTPA may represent a new and useful method to noninvasively monitor RP abnormalities in HF.Part One Analysis of peak time of renal scintigraphy with ^99mTc-DTPA in patients with heart failureObjective:Observe the changes of renal perfusion and renal function in patients with heart failure by time to peak perfusion changes in renal scintigraphy with ^99mTc-DTPA,and to explore the feasibility of early detection of renal function changes in HF.Methods:1.Systolic heart failure is based on left ventricular ejection fraction(LVEF)?45%.Patients with HF were classified into two categories according to the New York Heart Association(NYHA)functional class,i.e.,moderate HF with NYHA functional class I or II and severe HF with NYHA functional class III or IV.The control group with the age-matched subjects without HF.Analyzed their clinical characteristics and differences among the three groups.2.All the subjects underwent renal scintigraphy with ^99mTc-DTPA,the first-pass time-activity curve(TAC)of the renal scintigraph was recorded.The GFR was determined by Gate's method.The time to peak perfusion activity(T_p)in the study were obtained.The difference of T_P among the three groups was statistically analyzed.3.Receiver operating characteristic curve(ROC)was drawn to evaluate the predictive ability of T_P for heart failure and severe heart failure.Results:1.Compared with the control group,T_P was prolonged despite comparable GFRs between the control and HF groups.With the aggravation of heart failure,T_P was significantly prolonged:(41.63±12.22 s in severe HF vs.26.95±6.26 s in moderate HF vs.17.84±3.17 s in control,P<0.001),indicating that RP was damaged and gradually aggravated.2.In the changes of renal function in patients with heart failure,we found that the change of RP was earlier than the change of GFR,and earlier than the deterioration of clinical symptoms.3.According to the ROC curve results,T_P can be used to further judge whether heart failure or not,when T_P is 22s,it can be used to judge whether heart failure or not,and when T_P is 24s,it can be used to distinguish moderate and severe heart failure,and both of them have high specificity and sensitivity.Conclusions:1.^99mTc-DTPA renal imaging can noninvasively monitor the abnormal renal perfusion.In the changes of renal function in patients with HF,the change of RP is earlier than the change of GFR and the deterioration of clinical symptoms.2.In heart failure,T_P is prolonged.With the aggravation of heart failure,T_P is significantly prolonged,which can indicate that RP is damaged and gradually aggravated;T_P can be used to judge heart failure and assist clinical work.3.^99mTc-DTPA renal imaging is a new noninvasive method to monitor RP in patients with heart failure.Part Two Analysis of slope change characteristics of renal scintigraphy with ^99mTc-DTPA in patients with heart failureObjective:Observe the changes of renal perfusion and renal function in patients with heart failure by slope of TAC curve changes in renal scintigraphy with ^99mTc-DTPA,and to explore the feasibility of early detection of renal function changes in HF.Methods:1.Systolic heart failure is based on left ventricular ejection fraction(LVEF)?45%.Patients with HF were classified into two categories according to the New York Heart Association(NYHA)functional class,i.e.,moderate HF with NYHA functional class I or II and severe HF with NYHA functional class III or IV.The control group with the age-matched subjects without HF.Analyzed their clinical characteristics and differences among the three groups.2.All the subjects underwent renal scintigraphy with ^99mTc-DTPA,the first-pass time-activity curve(TAC)of the renal scintigraph was recorded.The GFR was determined by Gate's method.The slope of the perfusion phase(S_p),slope of the washout phase(S_w)in the study were obtained.The difference of S_p,S_w and FF(GFR/S_p)among the three groups was statistically analyzed3.Calculate the median value of the radioactivity count value at each time point of TAC,use the median value to calculate the corresponding derivative,and then fit the curve with the derivative value to obtain the curve slope change diagram of TAC.The slope of the perfusion phase(S_P),slope of the washout phase(S_W)and filtration fraction(FF)of TAC can be obtained.The differences of S_P,S_W and FF among the three groups are statistically analyzed.Results:1.There were significant differences about the first-pass time-activity curve in patients with HF and without HF:The slope of the perfusion phase(S_P),slope of the washout phase(S_W)became shallow and disappear with the aggravation of heart failure.It is suggested that the blood perfusion into renal(RP)and out of the renal is impaired or decreased.2.The filtration fraction(FF)of heart failure group was significantly different from that of without HF group:in heart failure,FF index increased and RP was damaged;the larger FF index was,the more serious RP was damaged.3.Subgroup analysis showed that there was no difference in RP between non ischemic heart failure patients and ischemic heart failure patients when the NYHA function level of the two groups was the same.In other words,renal perfusion changes in patients with heart failure have nothing to do with the cause,no matter what cause of heart failure will be manifested to renal perfusion damage.Conclusions:1.In heart failure,S_P and S_W became shallow;S_P and S_W disappear with the aggravation of heart failure;and FF index increased;Suggesting that renal perfusion(RP)was damaged and aggravated.2.There was no difference in RP between non ischemic heart failure patients and ischemic heart failure patients when the NYHA function level of the two groups was the same.Renal perfusion is impaired in heart failure,which has nothing to do with the cause of heart failure.3.Renal scintigraphy with ^99mTc-DTPA may represent a new and useful method to noninvasively monitor RP abnormalities in HF.