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* Department of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, and
Department of Hypertension and Preventive Nephrology, IRCCS Policlinico Multimedica, Sesto San Giovanni, Milan, Italy
Address correspondence to: Prof. Francesco Locatelli, Department of Nephrology and Dialysis, A. Manzoni Hospital, Via DellEremo 9, 23900 Lecco, Italy. Phone: +39-0341-489862; Fax: +39-0341-489860; E-mail: nefrologia{at}ospedale.lecco.it
| Abstract |
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(CREATE) study was designed from the hypothesis that, as anemia develops early in the course of CKD and nearly at the same time as cardiovascular disease, its earlier correction may provide better protection against the development of cardiovascular abnormalities. This randomized, multicenter, open-label, parallel-group trial involved 603 patients who had moderate anemia (hemoglobin 11 to 12.5 g/dl) and stage 3 to 4 CKD (estimated GFR 15 to 35 ml/min) and were randomly assigned to attain complete or partial anemia correction. The final results are due to be published within a few months, but the preliminary analyses do not show that complete anemia correction leads to any cardiovascular advantage, although the cardiovascular event rate was half that expected, possibly as a result of patient selection, trial effect, and improved medical care. The baseline findings also indicated that the burden of cardiovascular disease already is very high even in relatively early stages of CKD. | Introduction |
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There is concern, therefore, about the devastating impact of CVD during the early stages of CKD on the long-term clinical outcome of patients, and this underlines that the nephrologic treatment of patients with CKD should be focused mainly on strategies that aim to prevent the development of cardiovascular complications, rather than only slow the progression of renal impairment. In addition to hypertension, anemia has attracted increasing attention in the past 10 yr as one of the major factors that contribute to the development of cardiovascular abnormalities in patients with CKD.
| Association between Anemia and CVD: Observational Studies |
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Earlier studies considered lower reference hemoglobin (Hb) values than those that are recommended today (8,9); subsequently, observational studies of large patient cohorts considered reference Hb values of between 10 and 12 g/dl. Locatelli et al. (9) in the Lombardy Registry and Ma et al. (10) in a large number of prevalent hemodialysis patients with Medicare insurance studied extensively the association between the risk for mortality and hematocrit levels and found a clear association between lower probabilities of death and higher hematocrit levels. To clarify the relationship between survival and higher hematocrit levels, Collins et al. (11) studied a large cohort of incident hemodialysis patients (n = 66,761) and, after 1 yr of follow-up, found that high hematocrit levels were associated with a lower risk for death from all causes, although there was no significant difference in the risk between patients with hematocrit values of 33 to <36% and those with higher levels. A similar pattern was observed in the case of cardiac causes of death and hospitalization, except for the patients with hematocrit values of 36 to <39%, who were at significantly lower risk for cardiac-cause hospitalization than those with hematocrit values of 33 to <36%.
In addition to the data that come from large registries (e.g., U.S. Renal Data System) (10,11), the Dialysis Outcomes and Practice Patterns (DOPPS) study provides another very useful source of information. This prospective observational study has the advantage that it analyzed very large populations of adult hemodialysis patients after adjustment for many case-mix characteristics. The DOPPS I data showed that, after adjustment for demographics and comorbidities, the relative risks for mortality and all-cause hospitalization were, respectively, 5 and 6% lower for every 1-g/dl greater Hb concentration (relative risk 0.95 and 0.94; P
0.003 for both) (12). The analysis of 4591 prevalent hemodialysis patients from five European countries (Euro-DOPPS) (13) and 5517 prevalent hemodialysis patients from the United States who participated in DOPPS I (US-DOPPS) (14) led to similar findings.
Volkova and Arab (15) more recently undertook a systematic, evidence-based review of published observational studies to investigate anemia and mortality in dialysis patients and confirmed a consistent trend toward increased mortality with decreasing Hb levels. However, the association between high Hb values and survival advantage was inconsistent insofar as there was a nonsignificant association between lower mortality and Hb values of >11 g/dl in studies that used Hb 10 to 11 g/dl as the reference, whereas at least some of the studies that used the higher reference value of 11 to 12 g/dl found a significant decrease in mortality associated with higher Hb levels (15).
| Anemia Correction and Outcome Improvement |
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Other clinical trials that investigated the optimal Hb target that is required to obtain better survival started from the assumption that complete anemia correction would give the best results in terms of decreased morbidity and mortality and improved quality of life. In this regard, Besarab et al. (24) were the first to test the effect of normalized Hb levels on hard outcomes in a high-risk population of 1233 hemodialysis patients who were aged >65 yr and had clinical evidence of congestive heart failure or ischemic heart disease and of whom a significant percentage had grafts as a vascular access for hemodialysis. The trial was halted prematurely for reasons of safety and futility because vascular access thrombosis in the patients who were randomly assigned to normal hematocrit had reached statistical significance, and the trends in mortality/acute myocardial infarction were such that it was unlikely that any benefit would be reached. However, it has been suggested that the study population was affected by too many comorbidities to benefit from full anemia correction; in particular, a high percentage of grafts in a population of patients with severe cardiac disease were believed to increase the occurrence of vascular access thrombosis (and therefore morbidity and mortality) in the experimental group.
This disappointing experience did not detract from the idea that less complicated patients may benefit more, but Furuland et al. (25) were unable to demonstrate a significant reduction in mortality after Hb normalization; however, this trial involved a heterogeneous population and was not designed primarily to study mortality. Parfrey et al. (26) more recently carried out a randomized, double-blind study to compare lower and higher Hb targets (9.5 to 11.5 and 13.5 to 14.5 g/dl) in 596 incident hemodialysis patients without symptomatic cardiac disease or LV dilation. After a mean follow-up of 74 wk, the percentage change in the LV volume index was not significantly different between the two groups. Mortality was a secondary outcome and although there were fewer deaths among the patients who were randomly assigned to complete anemia correction, this was not statistically significant probably because of the relatively low percentage of events in both groups. It also is worth noting that the patients in the higher target group experienced a higher number of cerebrovascular disorders.
These findings do not indicate any major effect of complete anemia correction on survival in patients with CKD, but most of the data were obtained from heterogeneous studies that were not designed primarily to analyze mortality. The only exception is the one by Besarab et al. (24), but the generalizability of the results is limited by the fact that the patients were very compromised and there was a very high percentage of grafts as vascular access.
Another very important point that needs to be taken into account when considering the results of the majority of these randomized, clinical trials is that the achieved Hb levels very often were in the lower or upper range of the experimental and control group targets, respectively, namely very close to or within the target range of Hb levels that are recommended by current international guidelines (27,28). This possibly has reduced the statistical power of the studies and may partially explain the negative findings. Figures 1 and 2 summarize the Hb targets and achieved values in studies of dialysis patients (Figure 1) and patients with CKD stage 3 to 4 (Figure 2).
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Cardiovascular Reduction Early Anemia Treatment Epoetin Trial
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(CREATE) study is that as anemia develops early in the course of CKD and almost at the same time as CVD, the earlier correction of anemia may provide better cardiovascular protection. The trial involved 95 nephrology units in 22 European, Asian, and Latin American countries, and its primary end point was the change from baseline in the LV mass index within 1 yr; if no differences were found at the time of the interim analysis, then the study was to have been stopped. The second primary variable was the time to the first cardiovascular event, including sudden death, fatal or nonfatal myocardial infarction, acute heart failure, angina pectoris or cardiac arrhythmias that required hospitalization, fatal or nonfatal stroke, transient cerebral ischemic attack, and peripheral vascular disease (amputation, necrosis). The secondary end points included CKD progression and quality of life.
Patients were eligible for inclusion when they had moderate CKD (estimated GFR 15 to 35 ml/min), mild to moderate anemia (Hb 11.0 to 12.5 g/dl) secondary to CKD, and no severe hypertension (BP
170/95 mmHg). Any patients with advanced CVD or severe chronic heart failure were excluded from the study, as were those who were expected to reach ESRD within 6 mo of the start of the study. A total of 603 patients satisfied the inclusion and exclusion criteria and were randomly assigned to receive immediate treatment with epoetin
to obtain a target Hb level of 13 to 15 g/dl or to routine treatment with a target Hb of 10.5 to 11.5 g/dl (these patients received epoetin
only when their Hb levels decreased to <10.5 g/dl). The study ended as scheduled 2 yr after the final patient had been randomly assigned; the final results will be published soon, but the preliminary analyses did not show any cardiovascular advantage in complete anemia correction.
In addition to the expected data concerning the possibly positive effect of Hb normalization on patient morbidity and mortality, this trial provided an opportunity for collecting an enormous amount of information about the burden of CVD in patients with CKD. The preliminary baseline data indicate that the treatment groups were similar in terms of gender, age, Hb levels, renal function, baseline nephropathy, and BP (29). More interesting, there was a very high prevalence of hypertension as a qualitative variable in the population as a whole (nearly 80%), equally divided between the two groups; the same was true of the percentage of patients who were treated with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers at enrollment (nearly 60% in both groups). This is important when analyzing the results because it is widely known that hypertension can cause LVH and that therapy with angiotensin-converting enzyme inhibitors can both improve heart morphology and slow CKD progression.
Nearly half of the patients were affected by diabetic nephropathy or hypertensive renal disease. This is not surprising in itself because these two diseases are the leading causes of renal replacement therapy worldwide; however, it is notable because it underlines that this population is burdened by a particularly high cardiovascular risk not only because of CKD but also because of the frequent coexistence of diabetes and hypertension.
Although the study patients were selected deliberately on the grounds that they were in a relatively early phase of CKD, a significant percentage had clinically evident CVD at baseline: In addition to a high prevalence of hypertension, nearly one third of the patients already were affected by ischemic heart disease, congestive heart failure, valvulopathies, or electrocardiographic disturbances, and nearly 10% had cerebrovascular or peripheral vascular disease. The high prevalence of established CVD was reflected in their baseline LV geometry. Preliminary data showed that 64% had abnormal echocardiographic findings (29); in particular, nearly half of the population had an increased LV mass (28% had eccentric and 21% had concentric LVH), and an additional 15% had a normal LV mass but presented concentric remodeling. This is in line with other observations that showed a progressive increase in the frequency of LVH at more severe CKD stages (30).
However, the 5.8% rate of cardiovascular events during follow-up was lower than the expected 15%, probably because of the positive patient selection, trial effects, and/or optimized care, including careful BP control and use of cardioprotective agents. Mortality in fact was much less than the need for dialysis, which is in contrast with epidemiologic data concerning the CKD population as a whole (5,6).
| Conclusion |
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This formed the basis of the rationale of the CREATE study, which compared the effects of early and complete Hb normalization with those of partial anemia correction in a large sample of patients with stages 3 to 4. CKD. The preliminary baseline data of this study confirm the high burden of CVD in the conservative phase of CKD, thus emphasizing the importance of global medical care in this high-risk population.
| References |
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