Validation of an algorithm for predicting cardiac events in renal transplant candidates

Cardiac imaging for the assessment of patients being evaluated for kidney transplantation

Cardiac risk assessment before kidney transplantation has become widely accepted. However, the optimal patient selection and screening tool for cardiac assessment remain controversial. Clinicians face several challenges in this process, including the ever-growing pre-transplant population, aging transplant candidates, increasing prevalence of coronary artery disease, and scarcity of donor organs. Optimizing the cardiovascular risk profile in kidney transplant candidates is necessary to better appropriate limited donor organs and improve patient outcomes. Increasing waiting times from the initial evaluation for transplant candidacy to the actual transplant raises questions regarding re-testing and re-stratification of risk. In this review, we summarize and discuss the current literature on cardiac evaluation prior to kidney transplantation. We also propose simple evidence-based evaluation algorithms for initial and follow-up CAD surveillance in patients being wait-listed for kidney transplantation.

Assessing cardiovascular risk in chronic kidney disease patients prior to kidney transplantation: clinical usefulness of a standardised cardiovascular assessment protocol

Background

Despite pre-kidney-transplant cardiovascular (CV) assessment being routine care to minimise perioperative risk, the utility of such assessment is not well established. The study reviewed the evaluation and outcome of a standardised CV assessment protocol.

Methods

Data were analysed for 231 patients (age 53.4 ± 12.9 years, diabetes 34.6%) referred for kidney transplantation between 1/2/2012-31/12/2014. One hundred forty-three patients were high-risk (age > 60 years, diabetes, CV disease, heart failure, peripheral vascular disease) and offered dobutamine stress echocardiography (DSE); 88 patients were low-risk and offered ECG and echocardiography with/without exercise treadmill test.

Results

At the end of follow-up (579 ± 289 days), 35 patients underwent kidney transplantation and 50 were active on the waitlist. There were 24 events (CV or death), none were perioperative. One hundred fifteen patients had DSE with proportionally more events in DSE-positive compared to DSE-negative patients (6/34 vs. 7/81, p = 0.164). In 42 patients who underwent coronary angiography due to a positive DSE or ischaemic heart disease symptoms, 13 (31%) had events, 6 were suspended, 11 removed from waitlist, 3 wait-listed, 1 transplanted and 17 still undergoing assessment. Patients with significant coronary artery disease requiring intervention had poorer event-free survival compared to those without intervention (56% vs. 83% at 2 years, p = 0.044). However, the association became non-significant after correction for CV risk factors (HR = 3.17, 95% CI 0.51–19.59, p = 0.215).

Conclusions

The stratified CV risk assessment protocol using DSE in all high-risk patients was effective in identifying patients with coronary artery disease. The coronary angiograms identified the event-prone patients effectively but coronary interventions were not associated with improved survival.

A clinical-genetic approach to assessing cardiovascular risk in patients with CKD

Background

Coronary heart disease (CHD) is the primary cause of death in individuals with chronic kidney disease (CKD), but current equations for assessing coronary risk have low accuracy in this group. We have reported that the addition of a genetic risk score (GRS) to the Framingham risk function improved its predictive capacity in the general population. The aims of this study were to evaluate the association between this GRS and coronary events in the CKD population and to determine whether the addition of the GRS to coronary risk prediction functions improves the estimation of coronary risk at the earliest possible stages of kidney disease.

Methods

A total of 632 CKD patients, aged 35–74 years, who had Stage 4–5 CKD, were on dialysis, had a functioning renal transplant or had returned to dialysis after transplant failure were included and followed up for a mean of 9.3 years. The transitions between disease states and the development of coronary events were registered. The increase in predictive ability that was obtained by including the GRS was measured as the improvement in the C-statistic and as the net reclassification index.

Results

The GRS was independently associated with the risk of CHD (hazards ratio 1.34; 95% confidence interval 1.04–1.71; P = 0.022), especially in Stages 4 and 5 CKD, and kidney transplant patients. A coronary risk prediction function that incorporated chronic kidney disease (CKD) disease state, age, sex and the GRS had significantly greater predictive capacity (AUC 70.1, P = 0.01) and showed good reclassification (net reclassification improvement 28.6).

Conclusion

This new function, combining genetic and clinical data, identifies CKD patients with a high risk of coronary events more accurately, allowing us to prevent such events more effectively.

Prevalence and predictors of early cardiovascular events after kidney transplantation: evaluation of pre-transplant cardiovascular work-up

INTRODUCTION

Cardiovascular disease is the leading cause of mortality after renal transplantation. The purpose of this study was to analyze cardiovascular risk factors at transplantation, occurrence of cardiovascular events in the first year after transplantation and evaluate pre-transplant work-up.

MATERIAL AND METHOD

In total, 244 renal transplant recipients older than 50 years were included. The results of pre-transplant work-up, including clinical evaluation, electrocardiogram, echocardiography, myocardial perfusion testing and coronary angiography were analyzed.

RESULTS

Patients had multiple risk factors at inclusion on renal transplantation waiting list as high blood pressure (94.7%), dyslipidemia (81.1%), smoking (45.3%), diabetes (23.6%), past history of cardiovascular disease (21.3%) and obesity (12.7%). Following transplantation, 15.5% (n = 38) of patients experienced a cardiovascular event, including 2.8% (n = 7) acute coronary syndrome, 5.8% (n = 14) isolated increase in troponin level and 5.3% (n = 13) new onset atrial fibrillation. The pre-transplant parameters associated with a cardiovascular event were a past medical history of cardiovascular disease (HR = 2.06 [1.06-4.03], p = 0.03), echocardiographic left ventricular hypertrophy (HR = 2.04 [1.04-3.98], p = 0.037) and abnormal myocardial perfusion testing (HR = 2.25 [1.09 -5.96], p = 0.03). Pre-transplantation evaluation allowed the diagnosis of unknown coronary artery lesions in 8.9% of patients.

Prognostic value of cardiac tests in potential kidney transplant recipients: a systematic review

BACKGROUND

Whether abnormal myocardial perfusion scintigraphy (MPS), dobutamine stress echocardiography (DSE) or coronary angiography, performed during preoperative evaluation for potential kidney transplant recipients, predicts future cardiovascular morbidity is unclear. We assessed test performance for predicting all-cause mortality, cardiovascular mortality and major adverse cardiac events (MACE).

METHODS

We searched MEDLINE and EMBASE (to February 2014), appraised studies, and calculated risk differences and relative risk ratios (RRR) with 95% confidence intervals (95% CI) using random effects meta-analysis.

RESULTS

Fifty-two studies (7401 participants) contributed data to the meta-analysis. Among the different tests, similar numbers of patients experienced MACE after an abnormal test result compared with a normal result (risk difference: MPS 20 per 100 patients tested [95% CI, 0.11-0.29], DSE 24 [95% CI, 0.10-0.38], and coronary angiography 20 [95% CI, 0.08-0.32; P = 0.91]). Although there was some evidence that coronary angiography was better at predicting all-cause mortality than MPS (RRR, 0.69; 95% CI, 0.49-0.96; P = 0.03) and DSE (RRR, 0.72; 95% CI, 0.50-1.02; P = 0.06), noninvasive tests were as good as coronary angiography at predicting cardiovascular mortality (RRR, MPS, 0.89; 95% CI, 0.38-2.10; P = 0.78; DSE, 1.09; 95% CI, 0.12-10.05; P = 0.93), and MACE (RRR: MPS, 1.09; 95% CI, 0.64-1.86; P = 0.74; DSE, 1.56; 95% CI, 0.71-3.45; P = 0.25).

CONCLUSIONS

Noninvasive tests are as good as coronary angiography at predicting future adverse cardiovascular events in advanced chronic kidney disease. However, a substantial number of people with negative test results go on to experience adverse cardiac events.

Frequency and clinical predictors of coronary artery disease in chronic renal failure renal transplant candidates

BACKGROUND/AIMS

Cardiovascular diseases are major causes of mortality in chronic renal failure patients before and after renal transplantation. Among them, coronary disease presents a particular risk; however, risk predictors have been used to diagnose coronary heart disease. This study evaluated the frequency and importance of clinical predictors of coronary artery disease in chronic renal failure patients undergoing dialysis who were renal transplant candidates, and assessed a previously developed scoring system.

METHODS

Coronary angiographies conducted between March 2008 and April 2013 from 99 candidates for renal transplantation from two transplant centers in São Paulo state were analyzed for associations between significant coronary artery diseases (≥70% stenosis in one or more epicardial coronary arteries or ≥50% in the left main coronary artery) and clinical parameters.

RESULTS

Univariate logistic regression analysis identified diabetes, angina, and/or previous infarction, clinical peripheral arterial disease and dyslipidemia as predictors of coronary artery disease. Multiple logistic regression analysis identified only diabetes and angina and/or previous infarction as independent predictors.

CONCLUSION

The results corroborate previous studies demonstrating the importance of these factors when selecting patients for coronary angiography in clinical pretransplant evaluation.

How do We Manage Coronary Artery Disease in Patients with CKD and ESRD?

Chronic kidney disease (CKD) has been shown to be an independent risk factor for cardiovascular events. In addition, patients with pre-dialysis CKD appear to be more likely to die of heart disease than of kidney disease. CKD accelerates coronary artery atherosclerosis by several mechanisms, notably hypertension and dyslipidemia, both of which are known risk factors for coronary artery disease. In addition, CKD alters calcium and phosphorus homeostasis, resulting in hypercalcemia and vascular calcification, including the coronary arteries. Mortality of patients on long-term dialysis therapy is high, with age-adjusted mortality rates of about 25% annually. Because the majority of deaths are caused by cardiovascular disease, routine cardiac catheterization of new dialysis patients was proposed as a means of improving the identification and treatment of high-risk patients. However, clinicians may be uncomfortable exposing asymptomatic patients to such invasive procedures like cardiac catheterization, thus noninvasive cardiac risk stratification was investigated widely as a more palatable alternative to routine diagnostic catheterization. The effective management of coronary artery disease is of paramount importance in uremic patients. The applicability of diagnostic, preventive, and treatment modalities developed in nonuremic populations to patients with kidney failure cannot necessarily be extrapolated from clinical studies in non-kidney failure populations. Noninvasive diagnostic testing in uremic patients is less accurate than in nonuremic populations. Initial data suggest that dobutamine echocardiography may be the preferred diagnostic method. PCI with stenting is a less favorable alternative to CABG, however, it has a faster recovery time, reduced invasiveness, and no overall mortality difference in nondiabetic and non-CKD patients compared with CABG. CABG is associated with reduced repeat revascularizations, greater relief of angina, and increased long term survival. However, CABG is associated with a higher incidence of post-operative risks. The treatment chosen for each patient should be an individualized decision based upon numerous risk factors. CKD is associated with higher rates of CAD, with 44% of all-cause mortality attributable to cardiac disease and about 20% from acute MI. Optimal treatment including aggressive lifestyle modifications and concomitant medical therapy should be implemented in all patients to maximize benefits from either PCI or CABG. Future prospective randomized controlled trials with newer second or third generation DES and bioabsorbable DES are necessary to determine if PCI may be non-inferior to CABG in the future.

Cardiovascular risk assessment in kidney transplantation

Cardiovascular disease (CVD) remains the most common cause of death after kidney transplantation worldwide, with the highest event rate in the early postoperative period. In an attempt to address this issue, screening for CVD prior to transplant is common, but the clinical utility of screening asymptomatic transplant candidates remains unclear. A large degree of variation exists among both transplant center practice patterns and clinical practice guidelines regarding who should be screened, and opinions are based on mixed observational data with great potential for bias. In this review, we discuss the potential risks, benefits, and evidence for screening for CVD in kidney transplant candidates, and also the next steps to better evaluate and treat asymptomatic kidney transplant candidates.

Do clinical symptoms and signs predict reduced renal function among hospitalized adults?

BACKGROUND

Reduced renal function manifests as reduced glomerular filtration rate (GFR), which is estimated using the serum creatinine levels. This condition is frequently encountered among hospitalized adults. Renal dysfunction remains clinically asymptomatic, until late in the course of disease, and its symptoms and screening strategies are poorly defined.

AIM

We conducted this study to understand if the presence of renal dysfunction related clinical symptom and signs (either alone or in combination) can predict reduced GFR. Further, we aimed to determine if the combination of symptoms and signs are useful for prediction of different levels of reduced GFR.

SUBJECTS AND METHODS

We performed a cross-sectional clinical prediction study and included all consecutive patients admitted to the medical wards of the hospital. We used a renal dysfunction related clinical predictors as index tests and low estimated GFR ([eGFR] < 60 ml/min/1.73 m(2)) as a reference standard. We identified symptoms with a high likelihood ratio (LR) for prediction of low eGFR and constructed different risk score models. We plotted receiver operating curves for each score and used area under the curve (AUC) for comparison. The score with the highest AUC was considered as most discriminant. All statistical analysis was performed using the statistical software STATA (version 11.0, lake drive, Texas, USA).

RESULTS

A total of 341 patients participated in the study. None of the predictor variables had statistically significant LRs for eGFR less than 60 ml/min or eGFR less than 30 ml/min. Positive LRs were significant for prediction of eGFR < 15 ml/min for the presence of hypertension, vomiting pruritis, peripheral edema, hyperpigmentation, peripheral neuropathy and severe anemia. The best predictive model for eGFR less than 15 ml/min/1.73 m(2), included Age > 45 years, the presence of hypertension, vomiting, peripheral edema, hyperpigmentation, and severe anemia and had AUC of 0.82.

CONCLUSION

Clinical symptoms and signs are poorly predictive of reduced renal function, except for very low eGFR of less than 15 ml/min/1.73 m(2).

Cardiac testing for coronary artery disease in potential kidney transplant recipients

BACKGROUND

Patients with chronic kidney disease (CKD) are at increased risk of coronary artery disease (CAD) and adverse cardiac events. Screening for CAD is therefore an important part of preoperative evaluation for kidney transplant candidates. There is significant interest in the role of non-invasive cardiac investigations and their ability to identify patients at high risk of CAD. 

OBJECTIVES

We investigated the accuracy of non-invasive cardiac screening tests compared with coronary angiography to detect CAD in patients who are potential kidney transplant recipients.

SEARCH METHODS

MEDLINE and EMBASE searches (inception to November 2010) were performed to identify studies that assessed the diagnostic accuracy of non-invasive screening tests, using coronary angiography as the reference standard. We also conducted citation tracking via Web of Science and handsearched reference lists of identified primary studies and review articles.  

SELECTION CRITERIA

We included in this review all diagnostic cross sectional, cohort and randomised studies of test accuracy that compared the results of any cardiac test with coronary angiography (the reference standard) relating to patients considered as potential candidates for kidney transplantation or kidney-pancreas transplantation at the time diagnostic tests were performed. 

DATA COLLECTION AND ANALYSIS

We used a hierarchical modelling strategy to produce summary receiver operating characteristic (SROC) curves, and pooled estimates of sensitivity and specificity. Sensitivity analyses to determine test accuracy were performed if only studies that had full verification or applied a threshold of ≥ 70% stenosis on coronary angiography for the diagnosis of significant CAD were included.

MAIN RESULTS

The following screening investigations included in the meta-analysis were: dobutamine stress echocardiography (DSE) (13 studies), myocardial perfusion scintigraphy (MPS) (nine studies), echocardiography (three studies), exercise stress electrocardiography (two studies), resting electrocardiography (three studies), and one study each of electron beam computed tomography (EBCT), exercise ventriculography, carotid intimal media thickness (CIMT) and digital subtraction fluorography (DSF). Sufficient studies were present to allow hierarchical summary receiver operating characteristic (HSROC) analysis for DSE and MPS. When including all available studies, both DSE and MPS had moderate sensitivity and specificity in detecting coronary artery stenosis in patients who are kidney transplant candidates [DSE (13 studies) - pooled sensitivity 0.79 (95% CI 0.67 to 0.88), pooled specificity 0.89 (95% CI 0.81 to 0.94); MPS (nine studies) - pooled sensitivity 0.74 (95% CI 0.54 to 0.87), pooled specificity 0.70 (95% CI 0.51 to 0.84)]. When limiting to studies which defined coronary artery stenosis using a reference threshold of ≥ 70% stenosis on coronary angiography, there was little change in these pooled estimates of accuracy [DSE (9 studies) - pooled sensitivity 0.76 (95% CI 0.60 to 0.87), specificity 0.88 (95% CI 0.78 to 0.94); MPS (7 studies) - pooled sensitivity 0.67 (95% CI 0.48 to 0.82), pooled specificity 0.77 (95% CI 0.61 to 0.88)]. There was evidence that DSE had improved accuracy over MPS (P = 0.02) when all studies were included in the analysis, but this was not significant when we excluded studies which did not avoid partial verification or use a reference standard threshold of ≥70% stenosis (P = 0.09).  

AUTHORS' CONCLUSIONS

DSE may perform better than MPS but additional studies directly comparing these cardiac screening tests are needed. Absence of significant CAD may not necessarily correlate with cardiac-event free survival following transplantation. Further research should focus on assessing the ability of functional tests to predict postoperative outcome.

Coronary risk assessment and management options in chronic kidney disease patients prior to kidney transplantation

Cardiovascular disease remains the most important cause of morbidity and mortality among kidney transplant recipients. Nearly half the deaths in transplanted patients are attributed to cardiac causes and almost 5% of these deaths occur within the first year after transplantation. The ideal strategies to screen for coronary artery disease (CAD) in chronic kidney disease patients who are evaluated for kidney transplantation (KT) remain controversial. The American Society of Transplantation recommends that patients with diabetes, prior history of ischemic heart disease or an abnormal ECG, or age ≥50 years should be considered as high-risk for CAD and referred for a cardiac stress test and only those with a positive stress test, for coronary angiography. Despite these recommendations, vast variations exist in the way these patients are screened for CAD at different transplant centers. The sensitivity and specificity of noninvasive cardiac tests in CKD patients is much lower than that in the general population. This has prompted the use of direct diagnostic cardiac catheterization in high-risk patients in several transplant centers despite the risks associated with this invasive procedure. No large randomized controlled trials exist to date that address these issues. In this article, we review the existing literature with regards to the available data on cardiovascular risk screening and management options in CKD patients presenting for kidney transplantation and outline a strategy for approach to these patients.

Is standardized cardiac assessment of asymptomatic high-risk renal transplant candidates beneficial?

BACKGROUND

Perioperative cardiovascular events in renal transplantation are common and non-invasive cardiac stress tests are recommended in high-risk renal transplant candidates. In 2004, we introduced a standardized preoperative cardiac risk assessment programme with the aim of reducing perioperative cardiac events.

METHODS

Since 2004, all asymptomatic high-risk renal transplant candidates had to undergo non-invasive cardiac stress testing. Patients with a positive stress test went for a coronary angiography and if indicated for revascularization. The incidence of perioperative cardiac events (≤30 days of transplantation) was analysed in all high-risk patients who received a transplantation (screening group) and compared with high-risk renal transplant recipients evaluated in the 4 years before the introduction of the cardiac assessment programme (historical control group).

RESULTS

Since 2004, 227 of 349 asymptomatic high-risk renal transplant candidates underwent non-invasive cardiac stress testing. In 15 patients (6.6%), significant ischaemia was found. Ten of these 15 patients underwent coronary angiography (eight patients had significant coronary artery disease and in five patients, percutaneous coronary intervention was performed). One hundred and sixty of 349 renal transplant candidates have received renal transplantation so far (screening group). In the screening group, 6 perioperative cardiac events (3.8%) occurred compared to 13 perioperative events (7.6%) in the historical control group (n = 172) (P = 0.136).

CONCLUSIONS

The incidence of significant cardiac ischaemia in high-risk renal transplant patients was low and was followed by revascularization in a small percentage of patients. No significant decrease in perioperative cardiac events was observed after the introduction of the standardized cardiac assessment programme.

Topics in transplantation medicine for general nephrologists

Before transplantation, the general nephrologist is the primary resource for potential kidney transplantation recipients. After transplantation, the general nephrologist is increasingly managing transplant medications and complications. We provide evidence-based management strategies for common clinical issues. Linking our approach with the data allows the clinician to explore each subject in greater depth to tailor care to individual patients.

Cardiac evaluation prior to kidney transplantation

Kidney transplantation is the treatment of choice for most patients with stage 5 chronic kidney disease and end-stage renal disease (ESRD), offering improved quality of life and overall survival rates. However, the limited supply of available organs makes this a scarce resource. Cardiovascular complications continue to be the leading cause of mortality in the kidney transplant population, accounting for over 30% of deaths with a functioning allograft. Thus, preoperative cardiac risk assessment is critical to optimize patient selection and outcomes. Currently there is no consensus for cardiovascular evaluation in the chronic kidney disease and ESRD population prior to kidney transplantation; the recommendations of the American Society of Nephrology and American Society of Transplantation differ from those of the American Heart Association and the American College of Cardiology. Previously developed risk scores have also been used to risk stratify this population. In this review, we discuss two cases that illustrate the difficulties of interpreting the prognostic value of current testing strategies. We also discuss the importance of different tests for cardiovascular evaluation as well as previous nonkidney transplant specific risk scores used in the pre-kidney transplant population.

Cardiovascular risk assessment among potential kidney transplant candidates: approaches and controversies

Cardiovascular disease is the most common cause of death after kidney transplantation. However, uncertainties regarding the optimal assessment of cardiovascular risk in potential transplant candidates have produced controversy and inconsistency in pretransplantation cardiac evaluation practices. In this review, we consider the evidence supporting cardiac evaluation in kidney transplant candidates, generally focused on coronary artery disease, according to the World Health Organization principles for screening. The importance of pretransplant cardiac evaluation is supported by the high prevalence of coronary artery disease and the incidence and adverse consequences of acute coronary syndromes in this population. Testing for coronary artery disease may be performed noninvasively by using modalities that include nuclear myocardial perfusion studies and dobutamine stress echocardiography. These tests have prognostic value for mortality, but imperfect sensitivity and specificity for detecting angiographically defined coronary artery disease in patients with end-stage renal disease. Associations of angiographically-defined coronary artery disease with subsequent survival also are inconsistent, likely because plaque instability is more critical for infarction risk than angiographic stenosis. The efficacy and best methods of myocardial revascularization have not been examined in large contemporary clinical trials in patients with end-stage renal disease. Biomarkers, such as cardiac troponin, have prognostic value in end-stage renal disease, but require further study to determine clinical applications in directing more expensive and invasive cardiac evaluation.

Stress echocardiography for risk stratification in patients with end-stage renal disease undergoing renal transplantation

BACKGROUND

The predictive accuracy of stress echocardiography (SE) for adverse cardiac events has been variable in the population with end-stage renal disease undergoing renal transplantation (RT).

METHODS

We performed a retrospective study of 149 patients who had pretransplant SE before RT between 1997 and 2003. Patients were followed up for a mean of 2.85 years for major adverse cardiovascular events (MACE).

RESULTS

Of 149 patients studied, 139 had a negative SE, 65% were African American; 12 underwent cardiac catheterization. Only 1 patient required pre-RT revascularization. Sixteen MACE occurred over the follow-up period. SE had 37.5% sensitivity, 95.3% specificity, 33.3% positive predictive value, and 96.1% negative predictive value for MACE in the first year post-RT. First-year posttransplant event rates were 4.0% versus 30% (P < .001) for patients with a negative SE and positive SE, respectively. Multivariate predictors of MACE were positive SE (hazard ratio [HR] 7.64), hemoglobin less than 11 g/dL post-RT (HR 4.44), and calcium channel blocker use posttransplant (HR 2.90).

CONCLUSIONS

A negative SE has low incidence of MACE in this intermediate- to high-risk patient subset. A positive SE predicts a sevenfold higher risk of cardiovascular events regardless of the need for revascularization before the transplant.

Independent risk factors for progression of coronary atherosclerosis in hemodialysis patients

Not uncommonly, hemodialysis patients with normal results in myocardial perfusion tests can still have a cardiac event within 2 years of evaluation. We examined possible risk factors for progression of coronary atherosclerosis in hemodialysis patients. We prospectively evaluated ability of myocardial perfusion imaging carried out under pharmacologic stress to predict 2-year outcomes in 77 hemodialysis patients, specifically thallium-201 single-photon emission computed tomography (SPECT) using high-dose adenosine triphosphate as the stressor. The primary end-point was a cardiac event (cardiac death, non-fatal acute coronary syndrome, or hospitalization for acute ischemic heart failure). Factors independently influencing duration until a cardiac event in hemodialysis patients were identified using stepwise multiple regression analysis. Myocardial perfusion defects were shown in 36 patients. Patients with a perfusion defect were more likely to have cardiac events than those with normal perfusion (78% vs. 15%, P < 0.001). Time until occurrence of a cardiac event in hemodialysis patients showed a significant, independent association with known coronary artery disease [regression coefficient (RC) = -3.391, P = 0.046], elevated C-reactive protein (RC = -5.813, P = 0.005), and a reversible myocardial perfusion defect (RC = -7.386, P < 0.001). An analysis based on the 'best cut-off' of CRP as identified on the basis of the ROC curve augmented the positive and negative predict value of CRP for the prediction of coronary events to 65 and 74%, respectively. Myocardial perfusion SPECT and measuring the plasma concentration of CRP might be useful for the prediction of hemodialysis patients with progression of coronary atherosclerosis.

Complications, resource utilization, and cost of ABO-incompatible living donor kidney transplantation

BACKGROUND

The transplantation of living donor renal allografts across blood group barriers requires protocols to reduce and maintain anti-blood group antibody at safe levels. These protocols lead to an increase in resource utilization and cost of transplantation and may result in increased complications.

METHODS

In this retrospective study, we compared 40 ABO-incompatible to 77 matching ABO-compatible living donor renal allografts with respect to complications, resource utilization, and cost from day -14 to 90 days after transplantation.

RESULTS

Overall, surgery-related complications and resource utilization were increased in the ABO-incompatible group, primarily due to the desensitization protocol and antibody-mediated rejection. In the absence of rejection, the mean number of complications was similar for both groups. ABO-incompatible kidney transplantation was approximately 38,000 US dollars more expensive than ABO-compatible transplants, but was cost effective when compared to maintaining the patient on dialysis while waiting for a blood group compatible deceased donor kidney. Actuarial graft and patient survival was similar in the two groups.

CONCLUSIONS

We conclude that ABO-incompatible living donor kidney transplantation is a viable option for patients whose only donor is blood group incompatible despite the additional resource utilization and cost of therapy.

Deficiencies of cardiovascular risk prediction models for type 1 diabetes

OBJECTIVE

Cardiovascular risk prediction models are available for the general population (Framingham) and for type 2 diabetes (U.K. Prospective Diabetes Study [UKPDS] Risk Engine) but may not be appropriate in type 1 diabetes, as risk factors including younger age at diabetes onset and presence of diabetes complications are not considered. Therefore, our objective was to examine the accuracy of Framingham and UKPDS models for predicting coronary heart disease (CHD) in a type 1 diabetic cohort.

RESEARCH DESIGN AND METHODS

Ten-year follow-up data from the Pittsburgh Epidemiology of Diabetes Complications (EDC) study, a prospective cohort study of 658 subjects with childhood-onset type 1 diabetes diagnosed between 1950 and 1980 first seen in 1986-1988, were analyzed. EDC study data were used to calculate the 10-year probability of CHD (fatal CHD, nonfatal myocardial infarction, or Q-waves) applying to the Framingham and UKPDS equations.

RESULTS

Mean age at CHD onset was 39 years. When fatal/nonfatal myocardial infarction and CHD death were modeled, both the UKPDS and Framingham models showed significant lack of calibration (P < 0.0001) but moderate discrimination (0.76 UKPDS, 0.77 Framingham men, and 0.88 Framingham women). Both the UKPDS and Framingham models underestimated probability of events in highest risk deciles.

CONCLUSIONS

Currently available CHD models poorly predict events in type 1 diabetes. Future research should focus on determining the risk factors accounting for the lack of fit and developing prediction models specific to this high-risk group.

Risk stratification of patients with chronic kidney disease: results of screening strategies incorporating clinical risk scoring and dobutamine stress echocardiography

BACKGROUND

Cardiac disease is the principal cause of death in patients with chronic kidney disease (CKD). Ischemia at dobutamine stress echocardiography (DSE) is associated with adverse events in these patients. We sought the efficacy of combining clinical risk evaluation with DSE.

METHODS

We allocated 244 patients with CKD (mean age 54 years, 140 men, 169 dialysis-dependent at baseline) into low- and high-risk groups based on two disease-specific scores and the Framingham risk model. All underwent DSE and were further stratified according to DSE results. Patients were followed over 20 +/- 14 months for events (death, myocardial infarction, acute coronary syndrome).

RESULTS

There were 49 deaths and 32 cardiac events. Using the different clinical scores, allocation of high risk varied from 34% to 79% of patients, and 39% to 50% of high-risk patients had an abnormal DSE. In the high-risk groups, depending on the clinical score chosen, 25% to 44% with an abnormal DSE had a cardiac event, compared with 8% to 22% with a normal DSE. Cardiac events occurred in 2.0%, 3.1%, and 9.7% of the low-risk patients, using the two disease-specific and Framingham scores, respectively, and DSE results did not add to risk evaluation in this subgroup. Independent DSE predictors of cardiac events were a lower resting diastolic blood pressure, angina during the test, and the combination of ischemia with resting left ventricular dysfunction.

CONCLUSION

In CKD patients, high-risk findings by DSE can predict outcome. A stepwise strategy of combining clinical risk scores with DSE for CAD screening in CKD reduces the number of tests required and identifies a high-risk subgroup among whom DSE results more effectively stratify high and low risk.

Validation of a screening protocol for identifying low-risk candidates with type 1 diabetes mellitus for kidney with or without pancreas transplantation

BACKGROUND

Certain clinical risk factors are associated with significant coronary artery disease in kidney transplant candidates with diabetes mellitus. We sought to validate the use of a clinical algorithm in predicting post-transplantation mortality in patients with type 1 diabetes. We also examined the prevalence of significant coronary lesions in high-risk transplant candidates.

METHODS

All patients with type 1 diabetes evaluated between 1991 and 2001 for kidney with/without pancreas transplantation were classified as high-risk based on the presence of any of the following risk factors: age >or=45 yr, smoking history >or=5 pack years, diabetes duration >or=25 yr or any ST-T segment abnormalities on electrocardiogram. Remaining patients were considered low risk. All high-risk candidates were advised to undergo coronary angiography. The primary outcome of interest was all-cause mortality post-transplantation.

RESULTS

Eighty-four high-risk and 42 low-risk patients were identified. Significant coronary artery stenosis was detected in 31 high-risk candidates. Mean arterial pressure was a significant predictor of coronary stenosis (odds ratio 1.68; 95% confidence interval 1.14-2.46), adjusted for age, sex and duration of diabetes. In 75 candidates who underwent transplantation with median follow-up of 47 months, the use of clinical risk factors predicted all eight deaths. No deaths occurred in low-risk patients. A significant mortality difference was noted between the two risk groups (p = 0.03).

CONCLUSIONS

This clinical algorithm can identify patients with type 1 diabetes at risk for mortality after kidney with/without pancreas transplant. Patients without clinical risk factors can safely undergo transplantation without further cardiac evaluation.

Risk-stratified screening for ischemic heart disease in kidney transplant candidates

BACKGROUND

Few studies have examined the effectiveness of a risk-stratified approach to screening kidney transplantation candidates for ischemic heart disease (IHD).

METHODS

We retrospectively reviewed records from all adult patients (n = 514) placed on the deceased donor kidney transplantation waiting list at a single center between January 1992 and June 2000. During this time there was a consistent policy for high-risk patients to undergo noninvasive stress testing and/or coronary angiography. We examined screening tests, the resulting interventions, and the incidence of subsequent IHD events (myocardial infarction, angioplasty, bypass surgery, or IHD death) among those screened and not screened.

RESULTS

For 224 (43.6%) low-risk patients who were not screened, the actuarial incidence of an IHD event after listing (before or after transplantation) was only 0.5% at 1 year, 3.5% at 3 years, and 5.3% at 5 years. Screening 290 (56.4%) high-risk patients resulted in prophylactic angioplasty in 18 (6.2%), and bypass surgery in 8 (2.8%) before listing. After listing, 61 patients were screened, resulting in angioplasty in 6 (9.8%) and bypass surgery in 1 (1.6%). Of the 68 patients who ultimately had an IHD event after being placed on the waiting list, only 13 (19.4%) had not been screened.

CONCLUSIONS

A risk-stratified screening strategy effectively avoided unnecessary testing in 43.6%. However, the relatively low proportion of screened patients who underwent prophylactic angioplasty or bypass grafting raises the question of whether screening was effective in preventing IHD events.

Derivation and validation of a disease-specific risk score for cardiac risk stratification in chronic kidney disease

OBJECTIVE

Cardiac events (CE; cardiac death, non-fatal myocardial infarction and acute coronary syndrome) are the principal causes of death in patients with chronic kidney disease (CKD). We sought to devise and validate a cardiac risk score to risk-stratify patients with CKD.

METHODS

Clinical history and biochemical data were obtained in 167 CKD patients. CE were recorded over a median follow-up of 22 months. The hazard ratio (HR) of each independent variable using Cox regression analysis was used to derive a cardiac risk score for the prediction of events. The cardiac risk score was then applied to a validation population of 99 CKD patients to confirm its validity in predicting CE.

RESULTS

CE occurred in 20 patients in the derivation group. The independent predictors of CE were cardiac history (HR 9.83, P = 0.001), body mass index (BMI; HR 1.15, P = 0.002), dialysis duration (HR 1.24, P = 0.004) and serum phosphate (HR 4.29, P = 0.001). The resulting cardiac risk score (range 26-67) gave an area under the receiver operating characteristic curve of 0.86. CE occurred in 25 patients in the validation group; the ROC curve area was similar (0.84, P = 0.11). An optimal cardiac risk score cut-off of 50 assigned high risk to 29% of the derivation and 35% of the validation group (P = 0.26). CE occurred in 35 and 57% of the high-risk derivation and validation groups, respectively (P = 0.09), and in 2 and 8% of the low-risk groups (P = 0.15).

CONCLUSION

Application of a cardiac risk score using cardiac history, dialysis duration, BMI and phosphate identifies CKD patients at risk of future CE.

Prognostic value of stress myocardial perfusion imaging using adenosine triphosphate at the beginning of haemodialysis treatment in patients with end-stage renal disease

BACKGROUND

Non-invasive detection of coronary artery disease (CAD) remains difficult in patients with end-stage renal disease (ESRD). This study evaluated the ability of pharmacologic stress myocardial perfusion imaging to predict cardiac events in patients with ESRD.

METHODS

A prospective study was carried out in 49 consecutive patients with ESRD. Thallium-201 single photon emission computed tomography (SPECT) using high-dose adenosine triphosphate (ATP) was performed within 1 month of the beginning of haemodialysis. The study end-point was a cardiac event or the 1-year anniversary of the SPECT study.

RESULTS

Twenty-four patients (17 diabetics, 57% and seven non-diabetics, 37%) had myocardial perfusion defects. The remaining 25 patients had normal perfusion images. Fifteen patients had non-fatal cardiac events and two patients died of a cardiac cause. All patients who had non-fatal cardiac events underwent myocardial revascularization and survived until the end of follow-up. The 1-year cardiac event-free survival rate was 34% among patients with perfusion defects and 96% among patients without perfusion defects (P<0.001). The presence of a myocardial perfusion defect was the only independent predictor of 1-year cardiac events both in overall (HR, 49.91; 95% CI, 5.15-484.00; P<0.001) and in diabetic patients (HR, 33.72; 95% CI, 2.96-383.5; P = 0.005). Diabetes and an increased C-reactive protein were associated with the progression of CAD.

CONCLUSIONS

Normal myocardial perfusion imaging by stress thallium-201 SPECT using high-dose ATP performed within 1 month after the beginning of haemodialysis treatment is a powerful predictor of cardiac event-free survival in patients with ESRD.

Coronary angiography is the best predictor of events in renal transplant candidates compared with noninvasive testing

Guidelines for the detection of coronary artery disease (CAD) and assess of risk in renal transplant candidates are based on the results of noninvasive testing, according to data originated in the nonuremic population. We evaluated prospectively the accuracy of 2 noninvasive tests and risk stratification in detecting CAD (>or=70% obstruction) and assessing cardiac risk by using coronary angiography (CA). One hundred twenty-six renal transplant candidates who were classified as at moderate (>or=50 years) or high (diabetes, extracardiac atherosclerosis, or clinical coronary artery disease) coronary risk underwent myocardial scintigraphy (SPECT), dobutamine stress echocardiography, and CA and were followed for 6 to 48 months. The prevalence of CAD was 42%. The sensitivities and negative predictive values for the 2 noninvasive tests and risk stratification were <75%. After 6 to 48 months, there were 18 cardiac events, 9 fatal. Risk stratification (P=0.007) and CA (P=0.0002) predicted the crude probability of surviving free of cardiac events. The probability of event-free survival at 6, 12, 24, 36, and 48 months were 98%, 98%, 94%, 94%, and 94% in patients with <70% stenosis on CA and 97%, 87%, 61%, 56%, and 54% in patients with >or=70% stenosis. Multivariate analysis showed that the sole predictor of cardiac events was critical coronary lesions (P=0.003). Coronary angiography may still be necessary for detecting CAD and determining cardiac risk in renal transplant candidates. The data suggest that current algorithms based on noninvasive testing in this population should be revised.

Prognostic value of myocardial perfusion imaging in predicting outcome after renal transplantation

Cardiovascular disease is a significant cause of morbidity and mortality after renal transplantation. Pretransplant screening in a subset of these patients for occult coronary artery disease (CAD) may improve outcome. The objective of this study was to examine the outcome of 600 patients after renal transplantation for end-stage renal disease. Prospective outcome data were collected on 600 consecutive patients who had renal transplantation between 1996 and 1998 at our institution at 42 +/- 12 months after surgery. Stress single-photon emission computed tomographic (SPECT) myocardial perfusion imaging was performed in 174 patients before surgery, 136 (78%) of whom had diabetes mellitus. There were a total of 59 events: 17 cardiac deaths, 14 nonfatal myocardial infarctions, and 28 noncardiac deaths. There were 12 cardiac events and 11 noncardiac deaths among those who had SPECT myocardial perfusion imaging. In a multivariate analysis that included important risk factors, age (p = 0.03 and 0.003, respectively) and diabetes (p = 0.02 and 0.005, respectively) were the predictors of total events and cardiac events in patients who did not undergo stress SPECT perfusion imaging. In the subgroup who had stress perfusion imaging, an abnormal perfusion SPECT study was the only predictor of cardiac events (p = 0.006). The 42-month cardiac event-free survival rate was 97% in patients with normal SPECT images and 85% in patients with abnormal SPECT images (RR 5.04, 95% confidence interval 1.4 to 17.6, p = 0.006). Thus, there is a 2.8% event rate per year after renal transplantation, and approximately 50% of these events are noncardiac. In high-risk patients (most of whom had diabetes) with preoperative stress perfusion imaging, those with normal images had significantly lower cardiac events than those with abnormal images. These results have important implications in patient screening and postoperative management.