Blood levels of erythropoietin in congestive heart failure and correlation with clinical, hemodynamic, and hormonal profiles

CONGE5TlVE HEAHT FAlLURE

Blood Levels of Erythropoietin in Congestive Heart Failure and Correlation with Clinical, Hemodynamic, and Hormonal Profiles Massimo Volpe, MD, Cristina Tritto, MD, Ugo Testa, MD, Maria A. E. Rao, MD, Robert Martucci, MD, Angela Mirante, MD, lolandaEnea, MD, Rosaria Russo, MD, SperanzaRubattu, MD, GianLuigiCondorelli, MD, Sara Cangianiello,MD, Bruno Trimarco, MD, Cesare Peschle, MD, and Mario Condorelli,MD

Plasma levels of erythropoietin (mu/ml) were measured in patients with congestive heart failure(CHF)(n=lOs)andinacontrd~pofnormal subjects (n = 45). In normal subjects, pIas= ma levels of erythropoietln were 1.9 + 0.2. In patients with CHF, plasma levels of erythropoietin iB mvely according to New YOIIC Heart Association (NYHA) class (I: 1.4 f 0.2, n q 28; II: 5.4 f 0.8, n = 27; Ilk 9.8 + 2, n = 32; IV: 34 + 8, n = 21; F = 57.7, p
T

he kidney and its related hormonal mechanisms play a fundamental role in the patbophysiology of congestive heart failure (CI-IF).i~* A large body of evidence indicates that the renin-angiotensin system is significantly involved in the development of the disease.3-5 The activation of this system, in fact, contributes to the progressive deterioration of cardiac performance and clinical condition, leading toward the congestive stage through enhanced vasoconstriction and sodium and water retention. Whereas much is known about the reninangiotensin system in U-IF, the potential significance of other renal hormonal systems has been poorly investigated. Erythropoietin is a hormone mainly produced by the kidney, whose secretion is largely affected by renal oxygen s~pply.~ Beyond its promoting effect on erythropoiesis,7 this hormone raises blood pressure8 through an increase in peripheral resistance mediated by increases in red blood cell mass and blood viscosity8,9 as well as by systemic and renal vasoconstriction.8Jo Although a previous preliminary report conducted in a small experimental sample suggests that the circulating levels of erythropoietin are increased in CHF,” the relations between the increase in erythropoietin and the clinical, hemodynamic, and hormonal profiles in CHF remain unclear. The present study examines blood levels of erythropoietin in a large cohort of patients with CHF of varying etiology and correlates them with the severity of the disease, as well as with hemodynamic and hormonal parameters. METHODS

From the Department of Internal Medicine, School of Medicine, University of Napoli Federico II, Naples, and the Laboratory of Hematology and Gncology, Istituto Superiore di &nit& Rome, Italy. This study was supported in pan by Grant 91.00128 PF 41 from the Italian National Research Council (Consiglio Nazionale della Ricerche Institute). Manuscript received December 27, 1993; revised manuscript received March 14, 1994, and accepted March 18. Address for reprints: Massimo Volpe, MD, la Clinica Medica, Facolm di Medicina, Universita di Napoli Federico II, via S. Pansini, 5, 80131 Naples, Italy.

This study was performed with the approval of the institutional review board. All subjects gave informed consent. Forty-five normal nonsmoking subjects (32 men and 13 women; age range 19 to 62 years) served as a control group. None had a history of or physical or laboratory tindings showing any major disease, and none were taking any medication. One hundred eight patients (87 men and 21 women; age range 28 to 77 years) who were referred to our institution for evaluation of heart disease were studied after appropriate diagnostic procedures had been performed. Patients with acute renal failure, serum creatinine 21.5 mg/dl, primary liver or pulmonary diseases, type I diabetes mellitus, systemic arterial hypertension, recent myocardial infarction (within 2 months), and hematologic disease or hemoglobin

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concentrations ~11 g/d1 were excluded from the study. According to New York Heart Association (NYHA) criteria,r2 clinical symptomatology of the patients ranged from functional class I to IV The diagnosis of chronic CHF was established by history physical examination, chest x-ray, and by demonstration of a dilated, functionally impaired left ventricle or of valvular disease by Mand B-mode echocardiograms, radionuclide cineangiogram, and, in 45 patients, by left-sided cardiac catheterization. The etiology of chronic heart failure was considered idiopathic dilated cardiomyopathy in 35 patients; it was secondary to coronary artery disease in 62 when at least 1 previous myocardial infarction was documented or when coronary angiography had shown significant narrowing of the coronary epicardial arteries, and secondary to valvular disease in 11 patients. Long-term medications, including diuretic drugs, were discontinued 24 hours (at least 1 week for angiotensinconverting enzyme inhibitors) before blood was collected for hormonal measurements. At the time of the study, long-term therapy consisted of digoxin (n = 59), shortacting nitrates (n = 53), angiotensin-converting enzyme inhibitors (n = 63), and diuretic drugs (n = 59). Experimental protocol: Alcohol, caffeine, and physical exercise were all prohibited within 24 hours of the study. After admission to the clinic ward, all subjects were maintained on a daily diet containing 140 mEq of sodium, 50 mEq of potassium, and 1,500 ml of water. Daily 24-hour urine collections were analyzed for sodium, potassium, and creatinine excretion. The study was begun at 7:30 A.M. in the postabsorptive state with the subject sitting in a comfortable position after voiding. The temperature (22°C) and lights of the study room were maintained constant. Sixty minutes after insertion of the intravenous line into a superficial forearm vein, the following biochemical and hormonal measurements were obtained: blood urea and serum creatinine; hemoglobin concentration; complete blood count and peripheral hematocrit; erythrocyte sedimentation rate; serum glucose and bilirubin, aspartate and alanine aminotransferase and alkaline phosphatase; and prothrombin time. In addition, plasma renin activity, aldosterone concentrations, atrial natriuretic factor levels, and erythropoietin concentrations were measured. Plasma and red blood cell volumes were determined in 9 patients with NYHA class IV CHF and in 11 normal subjects. In patients with CHF, M-mode and B-mode echocardiograms were also recorded at baseline and left ventricular ejection fraction was determined by radionuclide ventriculography. Arterial blood pressure was measured by using the standard sphygmomanometric technique, and heart rate was measured by electrocardiographic lead II. To assess the influence of angiotensin-converting enzyme inhibition on plasma erythropoietin levels, measurements of hormones and echocardiography were repeated in 9 patients in NYHA class IV 3 weeks after the addition of enalapril (20 mg/day administered orally) to their long-term therapy. Nine patients in NYHA class IV maintained on a comparable long-term therapeutic regimen were studied at a 3-week interval without the addition of the angiotensin-converting enzyme inhibitor, and served as a control group.

Laboratory methods: Blood samples for plasma erythropoietin and atria1 natriuretic factor levels were collected on ice and centrifuged immediately (within 10 minutes); blood samples for plasma renin and aldosterone were collected at room temperature. The plasma was then separated and frozen until the time of assay, which did not exceed 4 weeks. All plasma samples were assayed according to a strictly blind code, which was disclosed at the end of the study. Plasma erythropoietin levels were measured as previously reported by using a sensitive immunoenzymatic assay with a detection threshold of 1 mu/ml (Amgen Diagnostics, Thousand Oaks, California). The intra- and interassay coefficients of variation were 2.5% to 10% and 10% to 15%, respectively. l3 Plasma renin activity was measured by enzymatic assay as previously reported from this laboratory. l4 Plasma immunoreactive atria1 natriuretic factor levels were determined by radioimmunoassay of the extracted plasma as previously described by our laboratory. l5 Plasma aldosterone concentrations were measured by radioimmunoassay using a commercial kit (DPC, Los Angeles, California). Plasma volume was evaluated by the isotopic dilution method using iodine-125-albumin (Sorb Biomedica, Saluggia, Italy). After withdrawal of a control sample, 5 pCi was injected as a bolus. Ten minutes after the injection, a single blood sample was taken. Standard whole blood and plasma samples were counted for a minimum of 10,000 radioactive decays. The background was counted for an equivalent time and subtracted from plasma, whole blood, and standard decays. Plasma volume was calculated by dividing total net-injected counts by plasma net counts. Packed red blood cell volume was obtained by subtracting plasma volume from whole blood volume. Previous studies have assessed the accuracy of the single lo-minute sample using serial consecutive blood samples.16 An indication of the accuracy of the procedure was given by comparing radioactive hematocrit with microhematocrit. The variation coefficient of duplicate measurements in our laboratory was 6 * 1%. Cardiac function a ssessment: Wide-angle, 2-dimensional echoes were recorded using a phased-array sector scanner (77020 AC, Hewlett-Packard Co., Andover, Massachusetts). All studies were videotaped on s-inch videocassette recorders equipped with a backspacer search module that allows frame-by-frame bidirectional playback. The video frame rate of the system is approximately 60 frames/s. All patients were studied in the supine position using multiple views through the apical window. Two views were selected for measurements: apical 4- and 2-chamber views. Left ventricular long axis was measured at end-diastole as the longest major axis in either of the 2 apical views. Measurements of left ventricular long axis were rounded off to the closest whole number to ensure reproducibility. Left ventricular end-diastolic area was measured using the largest of all left ventricular minor axes measured. Radionuclide assessment of ejection fraction was performed with the patient at rest in the supine position according to the methods previously reported from this laboratory. l7 Statistical analysis: Data are presented as mean + SEM. Distribution of the data was assessed by the ERYTHROPOIETININ HEART FAILURE 469

TABLE

I

Demographic,

Clinical

and Hormonal

Characteristics

of the Study

Normal Subjects (n = 45) Age (years) Sex [men:women) Body weight (kg) Systolic/diastolic blood pressure (mm Hg) Heart rate (beats/min) Blood urea nitrogen (mg/dl) Serum creatinine (mg/dl) Erythrocyte sedimentation rate (mm/hour) Hemoglobin concentration (g/dl) Serum alanine aminotransferase (U/L) Serum aspartate aminotransferase (U/L) Serum alkaline phosphatase (U/L) Serum total bilirubin (mg/dl) 24-hour urinary sodium excretion (mEq/24hours) 24-hour urinary potassium excretion (mEq/24 hours) ANF (pglml) PRA (@ml/hour) PA (pg/mU

35 i 32:13 71 f2 117&2/77+1 71 + 35 f 1 .o + 8+1 14.0 f 27 f 18fl 144f8 0.8 + 149 f 46 f 11 fl 2.4 It 136fll

2

1 1 0.02 0.2 2

0.1 15 3 0.2

Cause of heart failure (no.) (%) lschemic cardiomyopathy Idiopathic dilated cardiomyopathy Valvular disease Long-term therapy Direct-acting vasodilator Angiotensin-converting Diuretics Digitalis

enzyme

‘p ~0.001 vs normal subjects. tp co.05 vs normal subjects. ANF = atrial natriuretic factor;

inhibitor

NYHA = New York Heart Association:

Groups NYHA

I (n = 28) 53 + 22:6 74 is 128&3/82f2 68 f 39 * 1 .o f 8+1 14.1 f 27 + 18 f 156 f 0.8 f 142&16 48 k 34 * 2.0 f 113*15

2

II (n = 27)

Class Ill (n = 32)

56 f 2 2413 74 f 2 126*3/77f2 74 f 2 43 + 2 1.1 + 0.05 11 f2 14.2 + 0.3 24 f 3 19 * 1 155*11 0.6 f 0.1 154 f 14 55 f 5 72* 11’ 4.6 k 1.3 104*17

58 f 1 24:8 77 f 2 122&3/76*2 73 f 2 47 km2’ 1.1 +0.04* 15f2 13.5 f 0.2 28 zk 3 23 f 2 182 f 13 0.7 f 0.1 113+13 44 + 4 131 f 22 5.6 i 1 .Ot 125+19

11 (39.3) 14 (50.0) 3 (10.8)

17 (63) 9 (33.3) 1 (3.7)

21 (65.6) 8 (25.0) 3 (9.4)

9 14 9 8

16 19 13 13

20 18 19 20

2 2 3 0.03 0.3 3 1 11 1.0 4 5’ 0.2

PA = plasma aldosterone;

IV (n = 21) 59 f l7:4 77 * 116f4/77+2 87 f 52 f 1.2 * 14 f 13.1 f 24 k 22 * 241 f 1.7 * 110 + 46 f 270 f 11 .o f 270 k

2 3 3 4’ 0.05’ 2 0.3t 3 2 39 0.3 11 5 42’ 3.0t 93t

13 (61.9) 4 (19.1) 4 (19.1) 19 12 18 18

PRA = plasma renin activity.

Bartlett test. Chi-square analysis was used for comparison of descriptive parameters. Comparisons among the different groups were performed by using Kruskal-Wallis l-way analysis of variance. Comparisons within the same groups before and after treatment were performed by paired t test or Wilcoxon test as appropriate. Multiple regression analysis was performed using the SYSTAT package to detect correlations between independent variables and erythropoietin levels.

= 97.8, p
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SEPTEMBER 1. 1994

I

I

,

TABLE (NYHA

ii Radioactive Measurements of Blood class IV) and in Normal Subjects

Volume

in Patients

CHF = congestive

FiGURE 1. individual and mean piasma ieveis of erythropeie4tin (EPO) in normal wbJects (n=4S)andinlOSpatkmts with New York Heart Aswciation (NYHA) cen#astive heart failure (class I I 2(1; II 3 27; iii = 32; iv = 2q.**p
4,009 6,616 2,616 39.3

+ + f f

322 487 235 2

co.01 co.01 co.05 NS

Radioactive measurements of total biood, pias ma, and packed red blood ceil vdumes in patients with conge&ive heart failure: Table II summarizes the

measurements of plasma and red blood cell volumes obtained in subgroups of normal subjects (n = 11) and in patients with NYHA class IV CHF and high plasma erythropoietin levels (n = 9). The 2 groups had comparable body surface area. Total blood, plasma, and packed red blood cell volumes were consistently and significantly higher in patients with heart failure, whereas radioactively assessedperipheral hematocrit was not significantly different in the 2 groups, although it tended to be lower in patients with severe CHF.

were also measured before and after 3 weeks in 9 patients with stable CHF (NYHA class JV) who were maintained on the same chronic therapeutic regimen (“placebo” group), and in 9 patients in which enalapril was added to their long-term therapy. Plasma erythropoietin levels remained unchanged in the placebo group, in which also functional class and ejection fraction were unchanged at the end of the observation period (Figure 2B). In contrast, additional treatment with enalapril was associated in all patients with an improvement in symptomatology and ejection fraction (from 26.7 f 3% to 30.0 f 3%), and with marked reduction in plasma erythropoietin levels (from 43 f 14 to 12 + 3 mu/ml, p ~0.01) (Figure 2A). In this context, it is of interest that among these

1000

Patients (n = 9)

patients, those with the highest erythropoietin levels (i.e., >lOO mu/ml) had the most marked decline in plasma erythropoietin concentrations after a more effective treatment of CHF.

Effects of treatment of heart failure on plasma erythropdetin levels: Plasma erythropoietin levels

(mu/ml)

Failure

NYHA = New York Heart Association.

(NYHA functional class, ejection fraction, plasma renin activity, atrial natiuretic factor, and aldosterone), plasma renin activity, atrial natriuretic factor, and functional class were independent direct correlates of erythropoietin levels, while ejection fraction showed a significant inverse correlation. The most predictive factor of the erythropoietin levels, however, was plasma renin activity (standardized coefficient, 0.422; p
EPO

CHF

2,863 + 128 4,902 f. 234 2,028+119 41.3 fr 0.9

heart failure; EPO = etythropoietin;

Heart

I

Control Subjects (n = 11) Plasma EPO levels (mu/ml) Plasma volume (ml). Whole blood volume (ml) Red blood cell volume (ml) Hematocrit (%)

with Congestive

DISCUSSION

The present study was conducted in a large cohort of patients with CHF of different etiology and degree of cardiac dysfunction. The lindings of the present study demonstrate that blood levels of erythropoietin are increased in human CHF, and that this increase is related to the severity of the disease. In particular, plasma erythropoietin levels increased according to the NYHA

1

loo;; ,

IO;

.. ..

l-

;

:: i

;; .;.

........

I ........ . .................. ....

.I.... ... ..’ ............

.....

......

Normal

I

II

III

Subjects

NY HA

IV

Class

ERYTHROPOIETININ HEART FAILURE 471

Increasedproductionof erythropoietinin patients functionalclass.Thus,in patientswith no symptomsor U-IF mayreflectaconsignsof CHF (NYHA classI), levelswerestill within with themostsevereor advanced normalrange,whereasin patientswith moreseverecar- ditionof renalhypoxia.Althoughoxygensaturationwas thesignificantcorrelationwith reninactivdiac dysfunctionand overt symptomsof congestionat notmeasured, rest (NYHA classIV), levelsweremarkedlyelevated. ity observedin our studyindirectlysupportstheconcept In addition,a moreeffectivetreatmentof CHF produced thatrenalhypoperfusionmay contributeto erythropoiby addingangiotensin-converting enzymeinhibition to etin hyperproduction in CHF.This hypothesisis further long-termtherapyin a subsetof patientswith NYHA supportedby arecentreportshowingthatin patientswith classIV CHF andelevatedbaselineerythropoietinlev- CHF, renalplasmaflow and serumerythropoietinare els was associatedwith a significantand consistent significantlycorrelated. 26In fact, in our currentstudy, reductionin circulatinglevelsof the hormone.Finally, increasedblood levels of erythropoietinparalleledthe our findings show that in the patientswith the most severityof the cardiacdisease,asindicatedby correlasevereCHF, the elevatedcirculatinglevelsof erythro- tion with NYHA classes,aswell aswith theplasmaatripoietin wereassociatedwith increasedtotal red blood al natriureticfactorlevels,which aresensitivemarkers cell volume,asevaluatedby theradioiodinatedalbumin of the degreeof cardiacdysfunction,27 and to a lesser technique. degreeby the inversecorrelationwith left ventricular Erythropoietinis the most importanthormonalfac- ejectionfraction.Furthermore,our currentfindings,and tor regulatingerythropoiesis.7 The prevalentproduction consistentresultsobtainedin a small groupof patients site of erythropoietinin adult humanshasbeenidenti- with dilated cardiomyopathy,U demonstratethat the fiedin thekidney,andthemajor stimulusfor its release improvementof cardiacfunctioninducedby short-term is renalhypoxia.W The plasmaerythropoietinconcen- angiotensin-converting enzymeinhibition is associated trationsareincreasedwhenoxygenconsumptionof the with a significantandpromptreductionin plasmaerykidney exceedsthe supply,as observedin anemia,1g.20thropoietinlevels.In this regard,it shouldbementioned acuteexposureto high altitude,2tblood10ss,~~ andcon- thatenalaprilincreasesrenalbloodflow in patientswith genitalheartdisease. 23*24 In patientswith thislattercon- CHF.28Suchan effectmay augmentrenaloxygensupdition, erythrocytosisrepresents a physiologiccompen- ply with a consequentnegativefeedbackeffecton the satoryresponseto chronichypoxemia,25 andis thought erythropoietinreleasefrom the kidney. The significanceof the elevationof erythropoietin to be mostly accountedfor by the increasedrenalerythropoietinreleaseresultingfrom low oxygentensionin levelsin CHF cannotbe clarifiedby our study.In cyantheblood? otic heartdisease,hyperproduction of erythropoietinrepAlthoughthemechanismsunderlyingelevatedblood resentsa compensatoryattempt to augmentoxygen levelsof erythropoietinin patientswith CHF cannotbe delivery to peripheraltissuesthrougherythrocytosis?3 completelyclarifiedby our study,someof our findings On the otherhand,in adult patientswith CHF, it is a may contributeto the understanding of this phenome- commonobservation(alsoconlirmedby our study)that non.The observationthaterythropoietinlevelswerenot hematocritis oftenreducedratherthanincreased.U*26*2g correlatedwith renal or liver function in our patients This may appearin contrastto increasedproductionof indicatesthattheyareproducedby hypersecretion rather erythropoietin.However,radioactivemeasurements of thanthrougha reducedmetabolicclearanceassociated packedred blood cell volume performedin our study with CHE On theotherhand,patientswith severerenal demonstratethat the absoluteerythrocytemassis condysfunction(serumcreatinine21.5 mg/dl) or primary sistentlyincreasedat about25% in patientswith CHF liver diseasehadbeenexcludedfrom our study. and elevatederythropoietinlevels,and that the reduc-

EPO

150-

n1U/mI

. c

604

After

Before A

472

Before

FlOURE 2. EWecta of m@lotwd~ vwthtg l nzymo InhlbRlon (A) or pkcobo tmatmont (6) on Indlvldual and mean plasma l ythropolotln (EPO) Iovol8 In patbnta wRh Now York Heart Auocb tlcn clau Iv wn@atlvo hoart hllun. *p *O.Ol v8r8ua m8aulr8ln8nt8 cbtaln8d hdcr8 tr8atm8nt wlth anglotond~ vortlng enzyme InhlbRlon.

After B

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SEPTEMBER 1, 1994

tion of hematocrit is the mere consequence of the remarkable plasma volume expansion that occurs in these patients. Therefore, increased plasma erythropoietin levels are associated with a significant erythrocytosis that may contribute to increased peripheral oxygen delivery in patients with CHF, at the same time, however, erythrocytosis may cause an increase in blood viscosity. l. Bwger AC, Muldowney FP, Liebowitz MR. Role of the kidney in the pathogenesis of congestive heart failure. Circulation 1959;20:273-285. 2. Lamgh JH. Hormones and the pathogenesis of congestive heart failure: vasopressin, aldosterone, and angiotensin II. Circularion 196225: 1015-1021. a Cody RJ, Lamgh JH. The role of the renin-angiotensin-aldostemne system in the pathophysiology of chronic congestive heart failure. In: Cohn IN, ed. Drug Treatment of Heart Failure. New York: York Medical Books, 1983:35-51. 4. Francis GS, Goldsmith SR, Levine TB. Olivari MT, Cohn JN. The newohumoral axis in congestive heart failure. Ann Infern Med 1984;101:370-377. 1. Kubo SH. Neurohormonal activation and the response to converting enzyme inhibitors in congestive heart failure. Circularion 1990;8 l(supp1 III):III-107~III114. 8. Fritsch EF. The molecular biology and biochemistry of erythmpoietin. In: Garnick MB, ed. Erythm~ietin in Clinical Applications. New York: Marcel Dekker, 1990339-58. 7. Jacobson LO, Goldwasser E, Fried W, Plzak L. Role of kidney in erythmpoiesis. Nature 1957;179:633-634. 8. Satoh K, Masuda T, Ike& Y, Kurokawa S, Kamata K, Kiwada R, Takamoto T, Mamma F. Hemodynamic changes by recombinant erythropoietin therapy in hemodialyzed patients. Hypertension 1990,15:262-266. 9. Raine AEG. Hypertension, blood viscosity, and cardiovascular morbidity in renal failure: implications of erythmpoietin therapy. Lancer 1988; 1:97-99. 10. Heidenreich S, Rahn KH, Zidek W. Direct vasopressor effect of recombinant human erythmpoietin on renal resistance vessels. Kidney Int 1991;39:259-265. ll. Fyhrquist F, Karppinen K, Honkanen T, Saijonmaa 0, Row&f K. High serum erythmpoietin levels are normalized doting txatment of congestive heart failure with enalapril. J Intern Med 1989;226:257-260. 12. Goldman L, Hashimoto B, Cook EF, Loscalzo A. Comparative reproducibility and validity of systems for assessing cardiovascular functional class: advantages of a new specific activity scale. Circularion 1981;64: 1227-1234. 13. Baiocchi G, Scambia G. Benedetti P, Manichella G, Testa U, F’ilelli L, Martucci R, Foddai ML, Bizzi B, Mancuso S, Peschle C. Autologous stem cell transplantation: sequential production of hematopoietic cytokines underlying gramdo-

cyte recovery. Cancer Res 1993;53:1297-1303. l4. Volpe M, Tritto C, DeLuca N, Mele AF, Lembo G, Rubattu S, Romano M, deCampora P, Enea 1, Ricciardelli B, Trimarco B, Condorelli M. Failure of atrial nahiuretic factor to increase with saline load in patient with dilated cardiomyopathy and mild heart failure. J Clin Invest 1991;88:1481-1489, 15. Volpe M, Lembo G, DeLuca N, Lamenza F, Indolfi C, Condorelli GL, Trimarco B. Converting enzyme inhibition prevents the effects of atrial nattiuretic factor on arterial bamreflexes. Circulation 1990,82:1214-1221. 16. Raison 1, Achimastos A, Bouthier J, London G, Safar M. Intravascular volume, extracellular fluid volume, and total body water in obese and nonobese hypertensive patients. Am J Cardiol 1983;51:165-170. 17. Volpe M, Tritto C, DeLuca N, Rubattu S, Mele AF, Lembo G, Enea I, deCampora P, Rendina V, Romano M, Trimarco B, Condorelli M. Angiotensin-convefling enzyme inhibition restores cardiac and hormonal responses to volume overload in patients with dilated cardiomyopathy and mild heart failure. Circularion 199286: 180&1809. 18. Jelkmann W. Renal erythropoietin: properties and production. Rev Physiol Biochem Pharmacol 1986;104:139-215. 19. Erslev AJ, Cam J, Miller 0, Silver R. Plasma erythmpoietin in health and disease. Ann Ch Lab Sci 1980;10:250-257. 20. deKlerk G, Rosengarten J, Vet RJWM, Goudsmit R. Serum erythmpoietin titers in anemia. Blood 1981;58:116&1170. 2l. Milledge JS, Cotes PM. Serum erythropoietin in humans at high altitude and its relation to plasma renin. J Appl Physiol 1985;59:360-364. 22. Miller ME, Cronkite EP, Garcia JF. Plasma levels of immunoreactive erythropoietin after acute blood loss in man. Br J Haematol 198252545-549. 2a Tyndall MR, Teitel DF, Lutin WA, Clemens GK, D&man PR. Serum etythmpoietin levels in patients with congenital heart disease. J Pediatr 1987;110:538-544. 24. Giddimg SS, Stockman JA III. Erythmpoietin in cyanotic heart disease. Am HeartJ 1988;116:128-132. 21. Rosenthal A, Button LN, Nathan DG, Miettinen OS, Nadas AS. Blood volume changes in cyanotic congenital heart disease. Am J Cardiol 1971;7: 162-167. 26. Jensen J, Eiskjaer H, Bagger JP, Pedersen EB. Elevated level of erythropoietin in congestive heart failure. Relationship to renal perfusion and plasma twin. Jhtern Med 1993;233:125-130. 27. Raine AEG, Erne P, Biirgisser E, Miiller FB, Bolli P, Bukart F, Biihler FR. Atrial nahiuretic peptide and &al pressure in patients with congestive heart failure. N Engl J Med 1986;315:533-537. 28. Creager MA, Ha&tin JL, Bernard DB. Acute regional circulatory and renal hemodynamic effects of converting enzyme inhibition in patients with congestive heart failure. Circukzrion 1981;64:48?-489. 29. H&r HL, Leavy JA, Kessler PD, Kukin ML, Gottlieb SS, Packer M. The crythmcyte sedimentation rate in congestive heart failure. N En,@ J Med 1991;324: 353-358.

ERYTHROPOIETININ HEART FAILURE 473