1. health and fitness
2. disease

Cardiovascular Research 59 (2003) 538–548
www.elsevier.com / locate / cardiores
Review
The cardiovascular effects of erythropoietin
Kyle J. Smith, Anthony J. Bleyer, William C. Little, David C. Sane*
Sections of Cardiology and Nephrology, Department of Internal Medicine, Wake Forest University School of Medicine, Medical Center Boulevard,
Winston-Salem, NC 27157 -1045, USA
Received 13 March 2003; received in revised form 14 May 2003; accepted 2 June 2003
Abstract
Keywords: Angiogenesis; Endothelial function; Platelets; Renal function; Thrombosis / embolism
1. Introduction
The introduction of recombinant human erythropoietin
(rHuEpo) in 1989 marked a significant advance in the
management of anemia in end stage renal disease (ESRD).
Erythropoietin therapy is associated with an enhanced
quality of life [1], cognitive function, and activity level [2]
in ESRD patients. Non-dialysis indications include use in
patients with chronic renal failure not on dialysis with a
hematocrit less than 30%, treatment of anemia in
zidovudine-treated HIV-infected patients, and use in patients with non-myeloid malignancies on chemotherapy
[3]. The use of erythropoietin has broadened to include
patients with anemia from a variety of etiologies including
myelodysplastic syndromes [4], prematurity [5], as
prophylactic therapy to prevent anemia after surgery [6]
and to reduce blood transfusions to patients in intensive
care units [7].
Along with broader usage, there has been a trend
*Corresponding author. Tel.: 11-336-716-7533; fax: 11-336-7169188.
E-mail address: [email protected] (D.C. Sane).
towards increased doses of rHuEpo per patient. The mean
rHuEpo dose increased by 107–139% between 1990 and
1996 [8]. Recently, a new longer acting form of recombinant erythropoietin has become available [9]. Preliminary
studies suggest that erythropoietin therapy is beneficial and
safe in patients with CHF and anemia. Nevertheless, the
risk-to-benefit ratio of erythropoietin could be higher
outside the ESRD arena. For example, whereas renal
failure is associated with a bleeding diathesis [10], heart
failure may exhibit a neutral hemostatic balance or even a
pro-thrombotic state. Thus, as the potential uses of erythropoietin therapy increases, it is important to reconsider its
cardiovascular effects.
2. Biology of erythropoietin
Erythropoietin (Epo) has similar structure and signaling
mechanisms to the family of type I cytokines [11] and is
markedly induced by hypoxia [12]. Erythropoietin is
synthesized by peritubular cells in the cortex-medullary
Time for primary review 27 days.
0008-6363 / 03 / $ – see front matter  2003 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.
doi:10.1016 / S0008-6363(03)00468-1
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Erythropoietin is a hypoxia-induced hormone that is essential for normal erythropoiesis. The production of recombinant human
erythropoietin (rHuEpo) has revolutionized the treatment of anemia associated with chronic renal failure and chemotherapy, and has been
used as prophylaxis to prevent anemia after surgery. The erythropoietin receptor is widely distributed in the cardiovascular system,
including endothelial cells, smooth muscle cells and cardiomyocytes. Epo has potentially beneficial effects on the endothelium including
anti-apoptotic, mitogenic and angiogenic activities. On the other hand, some reports suggest that rHuEpo may have pro-thrombotic or
platelet-activating effects. Hypertension develops in 20–30% of renal patients treated with rHuEpo. Many patients with heart failure have
anemia. Despite some potential adverse effects, early studies in heart failure patients with anemia suggest that rHuEpo therapy is safe and
effective in reducing left ventricular hypertrophy, enhancing exercise performance and increasing ejection fraction. Further studies are
warranted to define the role of rHuEpo in chronic heart failure and other cardiovascular settings.
 2003 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.
K. J. Smith et al. / Cardiovascular Research 59 (2003) 538–548
border of the kidney [13] and in the liver during fetal and
neonatal development [14]. A variety of other tissues have
been reported to express erythropoietin including bone
marrow macrophages [15], trophoblasts [16], breast glands
[17], and astrocytes [18].
3. Novel erythropoiesis stimulating protein
3.1. Erythropoietin receptor ( EpoR)
EpoR is a transmembrane (type I) receptor with a
WSXWS motif in the extracellular domain. It belongs to
the cytokine receptor superfamily and consists of eight
exons (extracellular domains: 1–5; membrane spanning
domain: 6; intracellular domains: 7, 8) [21]. The intracellular domain does not possess any kinase activity. Epo
induces homodimerization of EpoR, with subsequent activation of the receptor associated Janus kinase 2 [22],
leading to tyrosine phosphorylation of EpoR, signal transducer and activator of transcription factor 5 (Stat 5) [23],
as well as a variety of other targets (Fig. 1). A number of
proteins with Src homology 2 (SH2) domains such as PI3
kinase become associated and are activated. PI3 kinase
suppresses apoptosis via activation of its downstream
effector Akt [24]. The Epo–EpoR interaction also leads to
activation of ras / MAPK pathways [25], and to activation
of nuclear factor-kB dependent transcription [26]. There
may be tissue or cell specific responses to Epo. For
example, it has been reported that MAP kinase, but not
JAK2-STAT5, is activated by exposure of rat VSMC to
Epo [27].
One of the major effects of the Epo–EpoR interaction is
a rise in intracellular calcium levels. Epo binding to EpoR
leads to phosphorylation of PLC-g1 [28]. PLC-g1 is then
translocated from the cytosol to the plasma membrane,
where it forms a complex with the EpoR. PLC-g1 activation leads to PIP2 hydrolysis with the generation of IP3 ,
which in turn induces the release of Ca 21 from intracellu-
lar stores and triggers 1 pS Ca 21 channel activity, which is
sustained by the extracellular Ca 21 entry through the
channel itself [28]. Calcium channel proteins may also
become phosphorylated during the EpoR mediated activation [29].
In addition to erythroid precursors [30], EpoR is also
expressed on megakaryocytes [31], VSMC [27,32], endothelial cells [32–34], skeletal myoblasts [35], neuronal
cells [36], kidney cells [37], breast carcinoma [38] and
ischemic retinal cells [39]. In the heart the EpoR is
expressed in the epicardium and pericardium [40]. A
soluble form of EpoR (containing exons 1–4) has been
described, resulting from alternate splicing [41,42]. Soluble EpoR has been suggested to contribute to resistance to
erythropoietin therapy [43], or to ineffective erythropoiesis
in myelodysplastic syndromes [44].
4. Erythropoietin and thrombosis
One of the potential side effects of erythropoietin
therapy is an increase in thrombotic events. In a prospective trial, 618 dialysis patients were randomized to achieve
a target hematocrit of 42% versus a target hematocrit of
greater than 30% in 615 control patients [45]. After 29
months, the relative risk of death in the high hematocrit
group was 1.3 (95% confidence interval 0.9–1.9), and the
trial was stopped. Factors such as exposure to intravenous
iron and decreased dialysis adequacy may have been
contributory, but the increased doses of erythropoietin
could also explain this result [45]. An increase in cardiovascular events, including vascular access thrombosis,
stroke and myocardial infarction, has been associated with
a rapid rate of rise in hemoglobin [19]. In the Canadian
Multicenter study, the overall rate of thrombosis was
0.28 / patient year in rHuEpo treated patients versus 0.05 /
patient year in controls [46]. In retrospective studies of
patients receiving chronic hemodialysis, rHuEpo therapy
resulted in a higher rate of PTFE graft thrombosis [47].
Darbepoetin alpha results in an increased rate of thrombotic events, including pulmonary embolism when administered to patients receiving chemotherapy [48].
The concerns regarding thrombosis have been evaluated
in an animal model. RHuEpo administration resulted in a
nearly 3-fold increase in the content of platelets in the
thrombi in an A–V shunt model, which reverted to normal
after cessation of erythropoietin administration [49]. A
variety of mechanisms have been cited for increased
thrombosis with erythropoietin therapy [50]. Erythrocytosis has been associated with thrombosis in young
healthy athletes [51], possibly because of increased blood
viscosity [52] or an enhancement of platelet attachment to
the subendothelium [53]. RHuEpo therapy has been reported to shorten the bleeding time even before the
correction of anemia [54], indicating that the elevation of
hematocrit cannot explain this effect. Some studies have
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Novel erythropoiesis stimulating protein (NESP,
Aranesp  ) was designed and expressed using recombinant
DNA technology [9]. NESP has several amino acid
substitutions, creating two new consensus N-linked carbohydrate attachment sites, which result in five oligosaccharide chains in NESP compared with three on rHuEpo.
NESP binds to the same receptor as does rHuEpo, although
at slightly reduced affinity [9]. The major benefit of NESP
is an increase in the serum half-life by approximately
3-fold over rHuEpo (25.3 vs. 8.5 h). NESP can be
administered weekly or every other week [9,19]. The
adverse events reported with NESP, including rates of
hypertension and vascular access thrombosis have been
similar to those with rHuEpo. Although NESP has several
amino acid substitutions, no neutralizing antibodies have
been detected, as has been reported for epoetin [20].
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found an increase in vWF, manifest as increased ristocetininduced platelet aggregation [54] after rHuEpo therapy.
Factor VIII antigen has also been increased in some studies
[55]. Enhanced thrombin generation has also been reported
after rHuEpo therapy, manifest as an increase in the TAT
complex in rHuEpo-treated dialysis patients, which peaked
at 2 months of therapy [56]. The increment in TAT was
comparable to that observed with myocardial infarction
and was higher than that reported in DVT or DIC [56].
Lower levels of protein C and S have been reported after
rHuEpo therapy, which could contribute to elevated prothrombotic markers [54,57]. Macdougall et al. [57] reported a reduction in total and free protein S, as well as
protein C after initiation of rHuEpo. Protein C levels at
baseline were 84.3% but decreased to 66.4% at 4 months,
and returned to baseline at 8 months [57]. Total protein S
decreased from 124.1% to 68.3% at 4 months and returned
to baseline at 8–12 months. A similar incremental reduction was noted in free protein S.
However, other studies have found minimal or no
adverse effects on hemostasis parameters [50]. In a group
of 17 patients with renal anemia including dialysis and
predialysis patients, a variety of coagulation parameters
were assessed before and at 3 months and 1 year after
beginning erythropoietin therapy [58]. The only significant
change noted was a decrease in the total level of protein S
at 3 months (from 131% to 120%), a change that did not
persist at 1 year [58]. Marchi et al. [59] studied 30
hemodialysis patients with native AV fistulae, 16 receiving
rHuEpo and 14 receiving a placebo, with a prospective
3-year follow-up. There were no differences in the rates of
stenosis of AV fistulae in the two groups. Furthermore, the
rHuEpo-treated group did not have a significant difference
in F112, Factor VII, Factor XII, t-PA antigen, PAI-1
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Fig. 1. Simplified diagram of erythropoietin-induced signal transduction. Erythropoietin induces homodimerization of the Epo receptor, with subsequent
activation and phosphorylation of JAK2. JAK2 phosphorylates EpoR providing docking sites for a variety of signaling molecules. STAT5 and PI3-K bind
to phosphorylated tyrosine residues on EpoR and are themselves activated by phosphorylation. Phosphorylated STAT5 forms a dimer which enters the
nucleus and induces transcription of target genes. PI3-K activates Akt, which inhibits apoptosis. Epo binding to EpoR also induces the activation of RAS
and PLC-g1. When PLCg1 is phosphorylated, it moves from the cytosol to the plasma membrane, where it hydrolyzes PIP2 to form IP3 . IP3 induces the
release of Ca 21 from intracellular stores, which in turn enhances extracellular Ca 21 entry through channel channels.
K. J. Smith et al. / Cardiovascular Research 59 (2003) 538–548
antigen, D-dimer, fibrinogen, protein C and S activities
compared with the placebo-treated group [59].
5. Effects on platelets
Table 1
Cellular effects of erythropoietin
Platelets
Increased production of microparticles
Enhanced platelet activation
Vascular endothelium
Mitogenic, chemotacticy and angiogenic effect
Increased endothelin production
Increased PAI-1 production
Vascular smooth muscle
Raises cytosolic Ca 21 concentration
Increases responses to norepinephrine, angiotensin II, and endothelin-1
Mitogenic effect
Cardiomyocytes
Enhances proliferation (neonatal)
Stimulates Na 1 ,K 1 activity
The effects of Epo on cellular components of the cardiovascular system
are summarized.
Epo binds to megakaryocytes, where it may contribute
to megakaryocyte maturation [31]. In patients treated with
rHuEpo, the platelet count may increase by 10–20% [66]
or substantially more in thrombocytopenic patients with
chronic liver disease [67]. Recent data from a porcine
model suggest that even modest rises in platelet count can
increase the propensity for arterial thrombosis [68].
RHuEpo therapy has been reported to increase the mean
platelet volume [69] with larger platelets being more active
than smaller platelets [70].
6. Erythropoietin effects on the vascular endothelium
Binding studies with radio-iodinated recombinant human
erythropoietin demonstrated approximately 27 000 receptors per endothelial cell with a Kd in the nanomolar range
[34]. Epo has a mitogenic and chemotactic effect on
HUVEC and bovine adrenal capillary endothelial cells [34]
(Table 1). Furthermore, Epo induces MMP-2 production,
proliferation and tube formation in EA.hy926 cells [71].
These effects likely contribute to the ability of Epo to
induce angiogenesis [71–74]. Using small pieces of human
myocardial tissue, Jaquet et al. demonstrated that Epo was
equally effective to VEGF in promoting capillary outgrowth [74].
Epo stimulates the production of endothelin [75], an
effect that is additive with Ang II or thrombin [72]. Epo
also induces the production of PAI-1 in cultured HUVEC
[33]. Six proteins have been identified that are tyrosine
phosphorylated following stimulation of cultured HUVEC
with rHuEpo. Of these proteins (94, 70, 42, 40, 29 and 25
kDa), one has been identified as STAT5 [76]. A differential display analysis of genes up-regulated in human
vascular endothelium has been performed [77]. Eight
genes were identified that were up-regulated by rHuEpo.
These included (i) proteins with vascular functions—
thrombospondin-1 and myosin regulatory light chain; (ii)
genes involved in gene transcription and / or translation
(c-myc purine-binding transcription factor PuF, tryptophanyl-tRNA synthetase, S19 ribosomal protein); (iii)
subunits of mitochondrial proteins related to energy transfer (NADH dehydrogenase subunit 6, cytochrome c oxidase subunit 1); and (iv) protein tyrosine phosphatase G1,
a regulator of signal transduction [77,78].
There is evidence for the activation of the endothelium
in vivo following intravenous rHuEpo administration [66].
In healthy male volunteers given rHuEpo 100 or 500 U / kg
three times weekly, there was a dose dependent increase in
soluble E-selectin, with an increase of more than 100% in
the 500 U / kg dose group and a significant, though smaller
increase in the low dose group. RHuEpo infusion also
increased soluble VCAM-1 but not soluble ICAM-1 [66].
Although the clinical consequences of this endothelial
activation are unknown, it is possible that enhanced
thrombogenicity could occur in patients with atherosclero-
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Several studies have documented a decrease in the
bleeding time of dialysis patients after initiation of rHuEpo
therapy [54,60]. Although this response could be due to
changes in the vessel wall or circulating proteins, several
lines of evidence suggest that at least part of the response
is from direct action on platelets. Hemodialysis patients
undergoing rHuEpo therapy have increased spontaneous
platelet aggregation in whole blood (Table 1), which
reverses by withdrawing erythropoietin and can be inhibited by aspirin administration [61].
Erythropoietin therapy in uremic rats leads to a normalization of the defect in thrombin stimulated rise in platelet
calcium influx [62]. RHuEpo therapy was associated with
increased Ca 21 uptake and increased Ca 21 stores in the
platelets [62]. Erythropoietin therapy of uremic patients
improves the intraplatelet signaling induced by thrombin
through tyrosine phosphorylation of proteins associated
with the cytoskeleton [63]. Enhanced transient platelet
reactivity has been observed in dialysis patients treated
with rHuEpo [64] and may contribute to a pro-thrombotic
effect. Ando and colleagues [65] reported elevated platelet
microparticles (PMP) in uremic pre-dialysis patients and
ESRD patients compared to healthy controls [65]. The use
of Epo in dialysis patients was associated with a significantly higher PMP count compared to untreated patients [65]. The infusion of rHuEpo at 100 U or 500 U / kg
in normal healthy male volunteers resulted in increased
percentages of P-selectin and CD63-positive platelets after
stimulation by TRAP [66]. Furthermore, circulating levels
of soluble P-selectin were also elevated, consistent with
increased in vivo platelet activation [66].
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sis or a history of thrombotic disorders. To evaluate the
effect of Epo on endothelial function in an animal model,
rabbits were given erythropoietin for 1 week [79]. Blood
pressure and vascular resistance were significantly less
responsive to endothelium dependent vasodilators after
rHuEpo therapy [79]. Responses to endothelium-independent vasodilators did not change with rHuEpo therapy.
These observations suggest that rHuEpo may selectively
suppress endothelial NO synthase activity. This finding is
in agreement with studies of cultured human endothelial
cells in which incubation with rHuEpo decreased basal and
ACh-stimulated NO production, and depressed NO
synthetase expression [80]. Although the direct effect of
Epo on the vascular endothelium may suppress NO
synthetase, there appears to be a compensatory increase in
NO production when Epo-induced erythrocytosis occurs.
Transgenic mice that overexpress human erythropoietin
have higher plasma nitrate levels than control mice [81], a
factor that helps prevent thrombosis despite a high hematocrit (0.85). Similarly, rats with erythrocytosis induced by
exogenous erythropoietin administration have enhanced
NO production, which helps maintain a normotensive state
in these animals [82].
RHuEpo has vasoconstrictor effects on isolated renal
and mesenteric resistance vessels [83] and high concentrations have been shown to induce contractions of rat
mesangial and aortic smooth muscle cells [84]. In cell
culture, rHuEpo raises the cytosolic calcium content of
VSMC, with stimulation of PKC and PLC-g1 [75,85]
likely contributing to this process [86]. Epo has a synergistic effect on rises in Ca 21 concentration in response to
norepinephrine [86,87], angiotensin II [85] and ET-1 [88].
RhuEpo increases the mRNA and protein expression of
angiotensin receptors types 1 and 2 (Table 1). The increase
in Ang II receptors sensitizes the cells to Ang II [89]. Epo
inhibits IL-1b stimulated NO production in rat VSMC
[86,90], potentially contributing to increased vasomotor
tone.
The increase of angiotensin II receptor on VSMC by
Epo not only affects vasomotor tone but also increases
gene products that could enhance cell proliferation (TGFb, IGF-II, EGF, PDGF, c-fos) [89]. Induction of the
expression of the proto-oncogenes c-myc, JunB, as well as
transient induction of c-fos has been reported [91], likely
contributing to the dose-dependent mitogenic effects of
Epo on SMC, as indicated by 3 H-thymidine incorporation
[91,92]. The mitogenic effects may be more pronounced
when VSMC from SHR were used compared with WKY
(Wistar–Kyoto) rats [93], suggesting that hypertension
may ‘prime’ VSMC for a proliferative response to Epo.
Furthermore, Epo induces Akt phosphorylation through the
8. Hypertension
Hypertension develops or worsens in 20–30% of renal
patients treated with rHuEpo [98]. Although the elevated
blood pressure can usually be treated without serious
consequences, hypertensive encephalopathy and seizures
occur rarely [99]. Increased blood pressure may occur in
dialysis patients as early as 2 weeks or up to 4 months
after the onset of therapy [98], most commonly in patients
receiving dialysis, who have a history of hypertension [98].
Animal models have mimicked the clinical scenario with a
rise in blood pressure after rHuEpo most likely to occur in
uremic animals with a predisposition to hypertension
[100]. Patients who are hypotensive may have a 10%
increase in BP after starting erythropoietin [98].
Postulated mechanisms for erythropoietin-induced hypertension include increased viscosity, enhanced vascular
reactivity due to the correction of hypoxia or vasoconstrictive responses due to the correction of anemia. Some
evidence suggests that rHuEpo may lead to catecholamine
release and activation of the renin–angiotensin system.
Cirillo et al. reported a significant association between
hematocrit and prevalence of hypertension [101], while
other studies have not demonstrated this correlation [102].
RHuEpo may have a direct vasopressor effect due to SMC
contraction at the level of the small resistance vasculature
[83]. The vasopressor effect may be due in part to the rise
in intracellular calcium levels, although in an animal
model, Roger et al. reported an increase in BP in uremic
SHR without an increase in cytosolic calcium levels [100].
Epo stimulates increased ET-1 release in cultured endothelial cells [72], in isolated hind legs of rats [103] and in
mice that overexpress erythropoietin [104]. ET-1 levels
have been reported to be elevated in some [105] but not all
[106] studies in patients receiving rHuEpo.
9. Effects of erythropoietin on the heart
RHuEpo produces a dose-dependent increase in neonatal
rat cardiomyocyte proliferation, which was inhibited by
tyrosine kinase, protein kinase C and phospholipase C
inhibitors [108]. Furthermore, ouabain, an inhibitor of
Na 1 ,K 1 -ATPase activity, inhibited the stimulation of
proliferation by rHuEpo [107] (Table 1). The effects of
rHuEpo on the myocyte cells appear to be related to the
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7. Erythropoietin effects on vascular smooth muscle
cells
PI3 kinase pathway in rat aortic VSMC [94] and phosphoAkT mediates an anti-apoptotic effect [95]. There is a
significant elevation in the expression of EpoR in the
hyperplastic intima from stenotic fistula in hemodialysis
patients receiving erythropoietin therapy [96]. Based on
these effects it is possible that Epo administration contributes to the accelerated progression of atherosclerosis in
dialysis patients [97].
Treatment
Treatment duration
Outcome
Ref.
ESRD Population
Mean Hct 2563% (n518)
Mean Hct 22.562% (n513)
Epo (50 U/kg) s.c. 33 per week to keep Hct 30–40%
Epo (40–120 IU/kg) 33 per week to keep Hct 30–35%
↑ SV, ↑ CI, ↑ MAP
↓LVEDD & LVESD, ↓LVEDV & LVESV, ↓ SV & CO, ↑EF (8/13 patients)
[115]
[117]
Mean Hct 23.762.5% (n525)
Mean Hct 22.964.3% (n515)
Epo (40–120 IU/kg) to goal Hct of 30–35%
Epo 33 per week i.v. to goal Hct of 35–38%
20 weeks
5–21 weeks
(mean 12 weeks)
$4 months
2867 weeks
↓ LVEDD & LVESD ↓ LVEDV & LVESV, ↑ EF & FS, ↓ SV & CO
↓ EDD & ESD ↓LV mass, ↑ EF
[118]
[119]
7.265.5 months
↓NYHA Class 3.66→2.66; LVEF 28→35%; hospitalizations ↓
[120]
8.262.7 months
Treatment group: NYHA class improved by 42.1%; LVEF ↑ 5.5%;
diuretics ↓ 51.3%; hospitalizations ↓ 79.0%
Increased Hb, peak VO 2 , and exercise duration in Epo-treated patients;
decreased exercise duration in control group
[124]
CHF Population
.Class III; Hb,12; EF,35 (n526)
Class III–IV, EF,40; Hb,11.5 (n532)
Class III–IV; HCT,35% (n526)
Nonrandomized; Epo, s.c. 2000 IU/week1200 mg i.v. Fe
until Hb.12
Randomized; Epo 4000 IU/week s.c.1200 mg i.v. Fe
until Hb.12.5 vs. placebo
Randomized; EPO 15–30 000 IU/week s.c. vs. placebo
3 months
Clinical trials of Epo in anemic patients with CHF and ESRD are shown.
[125]
K. J. Smith et al. / Cardiovascular Research 59 (2003) 538–548
Table 2
Cardiovascular effects of erythropoietin: clinical trials
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with intravenous iron to patients with CHF improved
NYHA functional class, EF, the number of hospitalized
days, the dose of diuretics and slowed the rate of progression of renal failure [120]. Similar findings were seen
in 32 patients with anemia and CHF randomized to
erythropoietin versus standard therapy [124]. Mancini et al.
performed a single blind randomized trial of Epo versus
placebo in patients with class III or IV CHF and HCT
,35% [125]. After 3 months of therapy, there was a
significant increase in peak VO 2 of 1.7 ml / kg / min in the
rHuEpo treated group compared with a decline of 0.5
ml / kg / min in the placebo cohort. The rHuEpo group also
had an increased exercise duration and distance time of 6
min and an improved quality of life score [125]. Epo
therapy was well tolerated without thrombotic complications or hypertension [125].
10. Future studies of erythropoietin therapy
The Cardiovascular Risk Reduction by Early Anemia
Treatment with Epoetin beta (CREATE) trial will investigate the effect of early anemia correction on cardiovascular
risk reduction in patients with renal impairment not yet on
renal replacement therapy [126]. The primary outcomes
will be the change in left ventricular mass index (LVMI)
assessed by echocardiography at 1 year and the time to
first cardiovascular events. There will be two arms in the
study: in the early intervention group, anemia correction
will begin with a Hb of 11–12.5 g / dl, with a target of
13–15 g / dl. In the late treatment arm, rHuEpo will be
administered for a Hb of ,10.5 g / dl with a target of
10.5–11.5 g / dl [126]. Erythropoietin may have additional
benefits on the heart that could further expand its cardiovascular applications. RHuEpo has a demonstrated
benefit as a neuroprotective agent through its anti-apoptotic, neurotrophic, antioxidant and angiogenic effects
[127]. RHuEpo also protects against ischemic cell death by
inhibiting the release of glutamate, a well-known neurotoxin, from neurons and attenuating glutamate toxicity
[39,128]. RhuEpo preserves mitochondrial function in the
skeletal muscle of patients with renal failure [129] and in
anoxic endothelial cells in culture [130]. Therefore clinical
studies may be warranted to determine if rHuEpo affords
cardiac protection in clinical scenarios such as ischemic
reperfusion injury.
11. Conclusions
The use of erythropoietin has resulted in profound
improvements in the health and quality of life of dialysis
patients and has been a landmark achievement in the care
of end-stage renal disease patients. Although classically
described as a hormone that stimulates erythroid precursors, erythropoietin is now known to have effects on
many cells and tissues. Erythropoietin stimulates endo-
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capacity of erythropoietin to stimulate Na 1 ,K 1 -ATPase
activity, likely secondary to the activation of tyrosine
kinase and protein kinase C. In the myocardium from
uremic rats, there is a decrease in high affinity binding
sites for [ 3 H]ouabain which is restored by erythropoietin
treatment. This finding suggests a mechanism for improved
myocardial contractility in renal failure patients after
rHuEpo administration [108].
Patients with cyanotic congenital heart disease have
elevated Epo levels, which can induce erythrocytosis, with
subsequent hyperviscosity, exacerbation of heart failure, as
well as seizures and thromboembolic events. Mice overexpressing the human Epo gene develop severe erythrocytosis (HCT50.80), resulting in decreased survival,
increased heart weights, and biventricular dilatation [109].
In contrast, mice lacking erythropoietin or erythropoietin
receptor die at embryonic days 13–15 and have reduced
number of proliferating cardiac myocytes, resulting in
ventricular hypoplasia [40]. This defect is probably due to
the severe anemia in these mice rather than a specific
dependence on the Epo–EpoR signaling pathway in normal heart development [110]. Suzuki et al. rescued EpoRnull mice from embryonic lethality by expressing an EpoR
transgene under the control of a GATA-locus hematopoietic regulatory domain. These mice expressed EpoR
exclusively in the hematopoietic lineage, and displayed
normal blood vessel formation and cardiac development
[110].
In dialysis patients, lower hemoglobin levels are associated with increased frequency of LVH, possibly through
renin–angiotensin system activation [111–113]. There is a
30% increased risk of developing LV mass for each 0.5
g / dl drop in hemoglobin [111]. Chronic anemia increases
the work load on the heart and increased LV mass is
observed in anemic patients with both ESRD and normal
renal function. Partial correction of the anemia of renal
failure by rHuEpo ameliorates LVH [114]. In ESRD
patients, the effect of rHuEpo on LVH may be dependent
upon the degree of anemia prior to initiation of rHuEpo
therapy [114]. In anemic patients with renal insufficiency,
rHuEpo therapy enhances cardiac output [115], reduces
sympathetic tone, increases peripheral vascular resistance,
improves coronary circulation and exercise tolerance
[116], induces regression of LVH [116–119] and increases
LVEF in patients with LV dysfunction [117–120] (Table
2).
More than 79% of patients with class IV CHF have a
Hb,12 g / dl, even if the degree of renal impairment is
only mild [120]. Hemodilution accounts for nearly half of
all cases of apparent anemia [121]. Several studies have
demonstrated that the presence of anemia is associated
with increased mortality in patients with CHF [121–123]
with an excess of approximately 13% for each 1 g / dl
decrease in the hemoglobin [122]. Importantly, the decreased survival was noted at relatively mild anemia
(,11.6 g / dl in women and ,12.6 g / dl in men) [122].
In an open label study, rHuEpo administration along
K. J. Smith et al. / Cardiovascular Research 59 (2003) 538–548
thelial cells with potential benefits (proliferation, angiogenesis) as well as potential detriments (PAI-1 and endothelin production). Erythropoietin can activate platelets, an
effect that could enhance thrombosis risks when this
therapy is used in patients with cardiovascular diseases.
Nevertheless, early studies have demonstrated the benefits
and safety of rHuEpo therapy for patients with CHF and
anemia. Additional studies are needed to confirm these
findings and to examine the effect of recombinant human
erythropoietin and NESP in other cardiovascular settings.
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