Haptoglobin Polymorphism Predicts 30-Day Mortality and Heart Failure in Patients With Diabetes and Acute Myocardial Infarction
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糖尿病学杂志 2005年第9期
1 Department of Cardiology, Rambam Medical Center, Haifa, Israel
2 Technion Faculty of Medicine, Haifa, Israel
ABSTRACT
Patients with diabetes presenting with acute myocardial infarction (AMI) have an increased rate of death and heart failure. Patients with diabetes homozygous for the haptoglobin (Hp) 1 allele (Hp 1-1) develop fewer vascular complications. We tested the hypothesis that Hp type is related to the outcome of patients with diabetes presenting with AMI. We prospectively assessed the relationship between Hp type and 30-day mortality and heart failure in 1,437 patients with AMI (506 with diabetes). Multivariate logistic regression identified a significant interaction between Hp type and diabetes status on these outcome measures. Hp type was not related to outcome among patients without diabetes. In contrast, Hp 1-1 was associated with a strong protective effect with regard to the primary end point of death (OR 0.14, P = 0.015) and for death and heart failure (OR 0.35; 95% CI 0.15eC0.86, P = 0.018) among patients with diabetes. Finally, among patients with diabetes, Hp 1-1 was associated with smaller infarct size. This study demonstrates that in patients with diabetes and AMI, the Hp type is an important determinant of clinical outcome and infarct size.
Patients with diabetes presenting with acute myocardial infarction (AMI) have a poor in-hospital and long-term prognosis (1). The excess in-hospital mortality and morbidity correlates primarily with an increased incidence of congestive heart failure (1,2), with heart failure developing at about twice the rate in patients with diabetes than in patients without diabetes (1). Diabetes is also a risk factor for cardiogenic shock in the setting of acute ischemic syndromes (3).
The susceptibility to diabetic complications is partially controlled by complex unknown genetic factors (4,5). One such genetic factor appears to be a functional allelic polymorphism in the haptoglobin (Hp) gene (6eC11). In humans, there are two major alleles, denoted 1 and 2, for the Hp gene (12,13). We have recently shown that patients who are homozygous for the Hp 1 allele (Hp 1-1) are at a lower risk of developing both microvascular (6,7,10) and macrovascular complications associated with diabetes (8,9,14). We have proposed that susceptibility to diabetic vascular disease conferred by the Hp type is the result of marked differences in the antioxidant protection against hemoglobin-induced oxidation provided by the Hp 1 and Hp 2 allelic protein products (15eC17). Specifically, we have shown in vitro and in vivo in mice genetically modified at the Hp locus that the Hp 1 and Hp 2 protein products differ in a diabetes-dependent fashion in their ability to prevent the release of redox active iron from hemoglobin and in the rate at which the hemoglobin-Hp complex is cleared via the CD163 scavenger receptor on monocyte/macrophages (15eC17).
In the present study, we sought to prospectively test the hypothesis that Hp type is related to the outcome of patients presenting with AMI. Because previous studies have shown that the effect of Hp type might be especially important in patients with diabetes (6eC10), we assessed whether the effect of Hp type in patients with AMI varied according to diabetes status using traditional interaction testing and stratified analyses.
Between July 2001 and June 2004, a total of 1,437 consecutive patients who presented with AMI were enrolled in the study. The clinical characteristics of the entire study population segregated by Hp type are listed in Table 1. There were no differences in these baseline characteristics between groups with different Hp types with the exception of fewer previous infarctions in the Hp 2-2 group. Of the 506 patients with known diabetes, 72 patients were receiving insulin treatment with or without oral agents (14%), 316 were receiving oral agents (63%), and 118 were on diet therapy (23%).
Over 30 days, 128 patients (8.9%) died and 357 patients (24.8%) developed heart failure. Likelihood ratio tests showed a significant interaction between Hp 1-1 and diabetes with regard to 30-day mortality in unadjusted (P = 0.01) and adjusted (P = 0.02) logistic regression models. Stratified Kaplan-Meier analyses indicated that in the group of patients with diabetes, Hp 1-1 was associated with lower mortality rates at 30 days (Fig. 1). The adjusted odds ratio for 30-day mortality for the Hp 1-1 group was 0.14 (P = 0.015) in patients with diabetes and 1.4 (P = 0.48) in patients without diabetes.
Results of multivariate modeling of the entire study population for the combined end point of death and heart failure found a strong protective effect of Hp 1-1 type with regard to the primary end point of 30-day mortality or heart failure (adjusted OR for Hp 1-1 0.54 [95% CI 0.33eC0.89], P = 0.01), whereas diabetes was associated with increased mortality and heart failure (adjusted OR 1.67 [95% CI 1.27eC2.21], P = 0.0002).
The interaction between Hp type and diabetes status was statistically significant in unadjusted (P = 0.007) and adjusted (P = 0.02) logistic regression models. Results of multivariate logistic regression models by stratification according to diabetes status are shown in Table 2. Hp 1-1 was associated with a small, nonsignificant reduction in 30-day death or heart failure among patients without diabetes. By contrast, Hp 1-1 was associated with a strong protective effect with regard to the primary outcome of death or heart failure among patients with diabetes after adjusting for numerous baseline clinical characteristics (Table 2).
The effect of the Hp polymorphism on infarct size as assessed by echocardiography was determined in a subgroup of patients (n = 1,120) with the first myocardial infarction. Wall motion score index was lower among patients with Hp 1-1 compared with patients with Hp 2-1 (P < 0.0001) and Hp 2-2 (P = 0.01) (Fig. 2A). To test whether diabetes modifies the effect of the Hp polymorphism on infarct size, we examined the effect of Hp type according to diabetes status in a two-way ANCOVA incorporating the main effect of Hp type and diabetes status. Two-way ANCOVA main effects indicated that Hp type (P < 0.0001) and diabetes status (P = 0.01) were significantly associated with higher wall motion score index. There was a significant interaction between Hp type and diabetes status in an unadjusted model containing only the main effects and an interaction term (P = 0.02) as well as in the adjusted model (P = 0.05).
Figure 2B shows adjusted means of wall motion score index obtained from the two-way ANCOVA model. In patients without diabetes, there was no significant difference in infarct size between patients with Hp 1-1 and patients with 2-1 (P = 0.12) or 2-2 (P = 0.99). However, Hp 1-1 was associated with a markedly lower infarct size compared with patients with Hp 2-1 (P = 0.009) or 2-2 (P = 0.02) among patients with diabetes.
Myocardial infarct size is a key prognostic factor in patients with acute infarction, most prominently in the hospital and throughout the first few months following infarction. The results of the present study suggest that in patients with diabetes, infarct size is dependent in part on Hp type. Patients with diabetes and Hp 2-1 or Hp 2-2 sustain larger infarcts, which may partially explain the higher mortality and heart failure in these patients. By contrast, patients with diabetes and Hp 1-1 have an infarct size comparable with that of nondiabetic patients.
The magnitude of the observed Hp typeeCdependent difference in wall motion index score might not be large enough to explain the increase in death and heart failure associated with Hp 2-1 and Hp 2-2 in the presence of diabetes. It does indicate, however, that preservation of left ventricular systolic function is an important determinant in the protective effect associated with Hp 1-1 in the setting of AMI.
The protective effect of having Hp 1-1 in patients with diabetes may be related to processes occurring before the onset of AMI. For example, patients with Hp 1-1 may have less extensive coronary disease (8,9,15) or a more developed collateral circulation (11); both factors are major determinants of the amount of myocardial necrosis after AMI.
Alternatively, the salutary effects of Hp 1-1 may also be related to events that take place in the ischemic myocardium after the onset of AMI. The antioxidant activity of the different Hp types differs markedly, with the Hp 1-1 protein conferring greater antioxidant properties compared with the other forms of the protein (15eC17). Oxidative stress plays a key role in processes that may affect outcome in the acute phase of AMI including platelet activation (18), reperfusion injury (19), and apoptosis (20), thus giving a relative advantage to patients with Hp 1-1.
RESEARCH DESIGN AND METHODS
This study was performed prospectively from July 2001 to June 2003 at the Rambam Medical Center in Haifa, Israel. We have recently briefly reported mortality data on a subset of the patients included here (21). However, this prior report did not include any analysis of heart failure or left ventricular function. Moreover, due to the smaller sample size of the initial cohort, the prior analysis was insufficiently powered to address potential interaction affects between Hp type and diabetes on cardiovascular end points.
All patients presenting to the intensive coronary care unit with acute myocardial infarction were eligible for entry into the study. The investigational review committee on human research approved the study protocol. Myocardial infarction was diagnosed based on the Joint European Society of Cardiology/American College of Cardiology criteria (22). Patients admitted >24 h from symptom onset were excluded.
Definition of diabetes.
Patients who had a clinical diagnosis of diabetes before enrollment into the study were classified as having diabetes. Patients were classified as having diabetes if the patient had been informed of the diagnosis by a physician before the admission and was taking oral antihyperglycemic agents, insulin, or receiving diet therapy.
Hp typing.
Hp phenotyping was performed on 10 e蘬 citrated plasma by polyacrylamide gel electrophoresis (11). We have previously established a 100% correspondence between the Hp phenotype as determined from serum by polyacrylamide gel electrophoresis and the Hp genotype as determined from DNA by PCR (23).
Study end points.
The primary end point of this study was death and the composite of death and heart failure occurring within 30 days of admission. Heart failure was diagnosed by the auscultation of rales over more than half of the lung field and pulmonary congestion on chest radiograph. Following hospital discharge, clinical end point information was acquired by reviewing the national death registry and by contacting each patient individually and independently reviewing the hospital course if the patient had been rehospitalized. The secondary end point was infarct size as determined by echocardiographic examination. This analysis was restricted to patients with no previous history of myocardial infarction.
Echocardiographic examination.
Assessment of left ventricular function by transthoracic echocardiography was performed on day 2eC3 of hospitalization in most patients or earlier if clinically indicated. The distribution of the Hp types and the incidence of major adverse clinical events of patients who did not undergo echocardiography were not different from those who did. Regional myocardial wall motion and left ventricular ejection fraction were determined from the echocardiogram by an observer blinded to the Hp type. For analysis of left ventricular function and wall motion abnormalities, we used the segmentation model according to the American Society of Echocardiography (24), with a higher index being associated with more severe contractile impairment.
Statistical analysis.
Baseline characteristics according to Hp type were compared by use of ANOVA for continuous variables and 2 test for categorical variables. Stepwise, multivariate logistic regression modeling was the primary statistical analysis used to determine the independent relationship between Hp type and other baseline characteristics to the primary end point. Multivariate linear regression analysis was used to determine the independent effect of Hp type on left ventricular function. Demographic and clinical variables that were considered to be possibly related to the primary end point or to left ventricular functional outcome, or both, were incorporated into the model, and the independent effect of Hp type was determined. Clinical variables for testing were chosen on the basis of their previously determined effect on 30-day mortality (25) and included age; sex; previous history of diabetes, hypertension, and myocardial infarction; smoking status; systolic blood pressure and heart rate upon admission; presence of ST-elevation infarction and anterior infarction; and use of reperfusion therapy.
Our analysis also focused on the possible interaction between Hp type and diabetes. The existence of an interaction between Hp type and diabetes was formally evaluated with the use of logistic regression models incorporating terms for the main effect of Hp type, the main effect of diabetes, and the interaction between Hp type and diabetes.
The influence of diabetes on Hp typeeCrelated differences in outcome was also assessed by a stratified analysis. In the stratified analysis, the predictive model developed for the entire study population was tested in subgroups of study patients defined by the presence or absence of diabetes. Differences were considered statistically significant at the two-sided P < 0.05 level. Statistical analyses were performed using the SPSS statistical software version 11.5.
ACKNOWLEDGMENTS
A.P.L. was supported by the Kennedy Leigh Charitable Trust, the Israel Science Foundation, the Binational Science Foundation, D Cure Diabetes Care in Israel, and the Russell Berrie Foundation.
FOOTNOTES
M.S. and D.A. contributed equally to this study.
A.P.L. has served on the advisory board of, holds stock in, and has received honoraria from Haptoguard.
AMI, acute myocardial infarction; Hp, haptoglobin
REFERENCES
Aronson D, Rayfield EJ, Chesebro JH: Mechanisms determining course and outcome of diabetic patients who have had acute myocardial infarction. Ann Intern Med126 :296 eC306,1997
Stone PH, Muller JE, Hartwell T, York BJ, Rutherford JD, Parker CB, Turi ZG, Strauss HW, Willerson JT, Robertson T, Braunwald E, Jaffe AS, the MILIS Study Group: The effect of diabetes mellitus on prognosis and serial left ventricular function after acute myocardial infarction: contribution of both coronary disease and diastolic left ventricular dysfunction to the adverse prognosis: the MILIS Study Group. J Am Coll Cardiol14 :49 eC57,1989
Holmes DR Jr, Berger PB, Hochman JS, Granger CB, Thompson TD, Califf RM, Vahanian A, Bates ER, Topol EJ: Cardiogenic shock in patients with acute ischemic syndromes with and without ST-segment elevation. Circulation100 :2067 eC2073,1999
Krolewski AS: Genetics of diabetic nephropathy: evidence for major and minor gene effects. Kidney Int55 :1582 eC1596,1999
Marre M, Jeunemaitre X, Gallois Y, Rodier M, Chatellier G, Sert C, Dusselier L, Kahal Z, Chaillous L, Halimi S, Muller A, Sackmann H, Bauduceau B, Bled F, Passa P, Alhenc-Gelas F: Contribution of genetic polymorphism in the renin-angiotensin system to the development of renal complications in insulin-dependent diabetes: Genetique de la Nephropathie Diabetique (GENEDIAB) study group. J Clin Invest99 :1585 eC1595,1997
Nakhoul FM, Zoabi R, Kanter Y, Zoabi M, Skorecki K, Hochberg I, Leibu R, Miller B, Levy AP: Haptoglobin phenotype and diabetic nephropathy. Diabetologia44 :602 eC604,2001
Levy AP, Roguin A, Hochberg I, Herer P, Marsh S, Nakhoul FM, Skorecki K: Haptoglobin phenotype and vascular complications in patients with diabetes. N Engl J Med343 :969 eC970,2000
Levy AP, Hochberg I, Jablonski K, Resnick HE, Lee ET, Best L, Howard BV: Haptoglobin phenotype is an independent risk factor for cardiovascular disease in individuals with diabetes: the Strong Heart Study. J Am Coll Cardiol40 :1984 eC1990,2002
Roguin A, Koch W, Kastrati A, Aronson D, Schomig A, Levy AP: Haptoglobin genotype is predictive of major adverse cardiac events in the 1-year period after percutaneous transluminal coronary angioplasty in individuals with diabetes. Diabetes Care26 :2628 eC2631,2003
Nakhoul FM, Marsh S, Hochberg I, Leibu R, Miller BP, Levy AP: Haptoglobin genotype as a risk factor for diabetic retinopathy (Letter). JAMA284 :1244 eC1245,2000
Hochberg I, Roguin A, Nikolsky E, Chanderashekhar PV, Cohen S, Levy AP: Haptoglobin phenotype and coronary artery collaterals in diabetic patients. Atherosclerosis161 :441 eC446,2002
Bowman BH, Kurosky A: Haptoglobin: the evolutionary product of duplication, unequal crossing over, and point mutation (Review). Adv Hum Genet12 :189 eC261, 453eC454,1982
Langlois MR, Delanghe JR: Biological and clinical significance of haptoglobin polymorphism in humans. Clin Chem42 :1589 eC1600,1996
Roguin A, Ribichini F, Ferrero V, Matullo G, Herer P, Wijns W, Levy AP: Haptoglobin phenotype and the risk of restenosis after coronary artery stent implantation. Am J Cardiol89 :806 eC810,2002
Asleh R, Marsh S, Shilkrut M, Binah O, Guetta J, Lejbkowicz F, Enav B, Shehadeh N, Kanter Y, Lache O, Cohen O, Levy NS, Levy AP: Genetically determined heterogeneity in hemoglobin scavenging and susceptibility to diabetic cardiovascular disease. Circ Res92 :1193 eC1200,2003
Asleh R, Guetta J, Kalet-Litman S, Miller-Lotan R, Levy AP: Haptoglobin genotype- and diabetes-dependent differences in iron-mediated oxidative stress in vitro and in vivo. Circ Res96 :435 eC441,2005
Melamed-Frank M, Lache O, Enav BI, Szafranek T, Levy NS, Ricklis RM, Levy AP: Structure-function analysis of the antioxidant properties of haptoglobin. Blood98 :3693 eC3698,2001
Yamagishi SI, Edelstein D, Du XL, Brownlee M: Hyperglycemia potentiates collagen-induced platelet activation through mitochondrial superoxide overproduction. Diabetes50 :1491 eC1494,2001
Ferrari R, Alfieri O, Curello S, Ceconi C, Cargnoni A, Marzollo P, Pardini A, Caradonna E, Visioli O: Occurrence of oxidative stress during reperfusion of the human heart. Circulation81 :201 eC211,1990
Maulik N, Yoshida T, Das DK: Oxidative stress developed during the reperfusion of ischemic myocardium induces apoptosis. Free Radic Biol Med24 :869 eC875,1998
Suleiman M, Kapeliovich MR, Roguin A, Aronson D, Meisel SR, Shochat M, Reisner SA, Hammerman H, Lotan R, Levy NS, Levy AP: Haptoglobin type and 30-day mortality in diabetic individuals presenting with acute myocardial infarction. Diabetes Care26 :2699 eC2700,2003
Alpert JS, Thygesen K, Antman E, Bassand JP: Myocardial infarction redefined: a consensus document of the Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol36 :959 eC969,2000
Koch W, Latz W, Eichinger M, Roguin A, Levy AP, Schomig A, Kastrati A: Genotyping of the common haptoglobin Hp 1/2 polymorphism based on PCR. Clin Chem48 :1377 eC1382,2002
Schiller NB, Shah PM, Crawford M, DeMaria A, Devereux R, Feigenbaum H, Gutgesell H, Reichek N, Sahn D, Schnittger I, Silverman NH, Tajik AJ: Recommendations for quantitation of the left ventricle by two-dimensional echocardiography: American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms. J Am Soc Echocardiogr2 :358 eC367,1989
Morrow DA, Antman EM, Giugliano RP, Cairns R, Charlesworth A, Murphy SA, de Lemos JA, McCabe CH, Braunwald E: A simple risk index for rapid initial triage of patients with ST-elevation myocardial infarction: an InTIME II substudy. Lancet358 :1571 eC1575,2001(Mahmoud Suleiman, Doron A)
2 Technion Faculty of Medicine, Haifa, Israel
ABSTRACT
Patients with diabetes presenting with acute myocardial infarction (AMI) have an increased rate of death and heart failure. Patients with diabetes homozygous for the haptoglobin (Hp) 1 allele (Hp 1-1) develop fewer vascular complications. We tested the hypothesis that Hp type is related to the outcome of patients with diabetes presenting with AMI. We prospectively assessed the relationship between Hp type and 30-day mortality and heart failure in 1,437 patients with AMI (506 with diabetes). Multivariate logistic regression identified a significant interaction between Hp type and diabetes status on these outcome measures. Hp type was not related to outcome among patients without diabetes. In contrast, Hp 1-1 was associated with a strong protective effect with regard to the primary end point of death (OR 0.14, P = 0.015) and for death and heart failure (OR 0.35; 95% CI 0.15eC0.86, P = 0.018) among patients with diabetes. Finally, among patients with diabetes, Hp 1-1 was associated with smaller infarct size. This study demonstrates that in patients with diabetes and AMI, the Hp type is an important determinant of clinical outcome and infarct size.
Patients with diabetes presenting with acute myocardial infarction (AMI) have a poor in-hospital and long-term prognosis (1). The excess in-hospital mortality and morbidity correlates primarily with an increased incidence of congestive heart failure (1,2), with heart failure developing at about twice the rate in patients with diabetes than in patients without diabetes (1). Diabetes is also a risk factor for cardiogenic shock in the setting of acute ischemic syndromes (3).
The susceptibility to diabetic complications is partially controlled by complex unknown genetic factors (4,5). One such genetic factor appears to be a functional allelic polymorphism in the haptoglobin (Hp) gene (6eC11). In humans, there are two major alleles, denoted 1 and 2, for the Hp gene (12,13). We have recently shown that patients who are homozygous for the Hp 1 allele (Hp 1-1) are at a lower risk of developing both microvascular (6,7,10) and macrovascular complications associated with diabetes (8,9,14). We have proposed that susceptibility to diabetic vascular disease conferred by the Hp type is the result of marked differences in the antioxidant protection against hemoglobin-induced oxidation provided by the Hp 1 and Hp 2 allelic protein products (15eC17). Specifically, we have shown in vitro and in vivo in mice genetically modified at the Hp locus that the Hp 1 and Hp 2 protein products differ in a diabetes-dependent fashion in their ability to prevent the release of redox active iron from hemoglobin and in the rate at which the hemoglobin-Hp complex is cleared via the CD163 scavenger receptor on monocyte/macrophages (15eC17).
In the present study, we sought to prospectively test the hypothesis that Hp type is related to the outcome of patients presenting with AMI. Because previous studies have shown that the effect of Hp type might be especially important in patients with diabetes (6eC10), we assessed whether the effect of Hp type in patients with AMI varied according to diabetes status using traditional interaction testing and stratified analyses.
Between July 2001 and June 2004, a total of 1,437 consecutive patients who presented with AMI were enrolled in the study. The clinical characteristics of the entire study population segregated by Hp type are listed in Table 1. There were no differences in these baseline characteristics between groups with different Hp types with the exception of fewer previous infarctions in the Hp 2-2 group. Of the 506 patients with known diabetes, 72 patients were receiving insulin treatment with or without oral agents (14%), 316 were receiving oral agents (63%), and 118 were on diet therapy (23%).
Over 30 days, 128 patients (8.9%) died and 357 patients (24.8%) developed heart failure. Likelihood ratio tests showed a significant interaction between Hp 1-1 and diabetes with regard to 30-day mortality in unadjusted (P = 0.01) and adjusted (P = 0.02) logistic regression models. Stratified Kaplan-Meier analyses indicated that in the group of patients with diabetes, Hp 1-1 was associated with lower mortality rates at 30 days (Fig. 1). The adjusted odds ratio for 30-day mortality for the Hp 1-1 group was 0.14 (P = 0.015) in patients with diabetes and 1.4 (P = 0.48) in patients without diabetes.
Results of multivariate modeling of the entire study population for the combined end point of death and heart failure found a strong protective effect of Hp 1-1 type with regard to the primary end point of 30-day mortality or heart failure (adjusted OR for Hp 1-1 0.54 [95% CI 0.33eC0.89], P = 0.01), whereas diabetes was associated with increased mortality and heart failure (adjusted OR 1.67 [95% CI 1.27eC2.21], P = 0.0002).
The interaction between Hp type and diabetes status was statistically significant in unadjusted (P = 0.007) and adjusted (P = 0.02) logistic regression models. Results of multivariate logistic regression models by stratification according to diabetes status are shown in Table 2. Hp 1-1 was associated with a small, nonsignificant reduction in 30-day death or heart failure among patients without diabetes. By contrast, Hp 1-1 was associated with a strong protective effect with regard to the primary outcome of death or heart failure among patients with diabetes after adjusting for numerous baseline clinical characteristics (Table 2).
The effect of the Hp polymorphism on infarct size as assessed by echocardiography was determined in a subgroup of patients (n = 1,120) with the first myocardial infarction. Wall motion score index was lower among patients with Hp 1-1 compared with patients with Hp 2-1 (P < 0.0001) and Hp 2-2 (P = 0.01) (Fig. 2A). To test whether diabetes modifies the effect of the Hp polymorphism on infarct size, we examined the effect of Hp type according to diabetes status in a two-way ANCOVA incorporating the main effect of Hp type and diabetes status. Two-way ANCOVA main effects indicated that Hp type (P < 0.0001) and diabetes status (P = 0.01) were significantly associated with higher wall motion score index. There was a significant interaction between Hp type and diabetes status in an unadjusted model containing only the main effects and an interaction term (P = 0.02) as well as in the adjusted model (P = 0.05).
Figure 2B shows adjusted means of wall motion score index obtained from the two-way ANCOVA model. In patients without diabetes, there was no significant difference in infarct size between patients with Hp 1-1 and patients with 2-1 (P = 0.12) or 2-2 (P = 0.99). However, Hp 1-1 was associated with a markedly lower infarct size compared with patients with Hp 2-1 (P = 0.009) or 2-2 (P = 0.02) among patients with diabetes.
Myocardial infarct size is a key prognostic factor in patients with acute infarction, most prominently in the hospital and throughout the first few months following infarction. The results of the present study suggest that in patients with diabetes, infarct size is dependent in part on Hp type. Patients with diabetes and Hp 2-1 or Hp 2-2 sustain larger infarcts, which may partially explain the higher mortality and heart failure in these patients. By contrast, patients with diabetes and Hp 1-1 have an infarct size comparable with that of nondiabetic patients.
The magnitude of the observed Hp typeeCdependent difference in wall motion index score might not be large enough to explain the increase in death and heart failure associated with Hp 2-1 and Hp 2-2 in the presence of diabetes. It does indicate, however, that preservation of left ventricular systolic function is an important determinant in the protective effect associated with Hp 1-1 in the setting of AMI.
The protective effect of having Hp 1-1 in patients with diabetes may be related to processes occurring before the onset of AMI. For example, patients with Hp 1-1 may have less extensive coronary disease (8,9,15) or a more developed collateral circulation (11); both factors are major determinants of the amount of myocardial necrosis after AMI.
Alternatively, the salutary effects of Hp 1-1 may also be related to events that take place in the ischemic myocardium after the onset of AMI. The antioxidant activity of the different Hp types differs markedly, with the Hp 1-1 protein conferring greater antioxidant properties compared with the other forms of the protein (15eC17). Oxidative stress plays a key role in processes that may affect outcome in the acute phase of AMI including platelet activation (18), reperfusion injury (19), and apoptosis (20), thus giving a relative advantage to patients with Hp 1-1.
RESEARCH DESIGN AND METHODS
This study was performed prospectively from July 2001 to June 2003 at the Rambam Medical Center in Haifa, Israel. We have recently briefly reported mortality data on a subset of the patients included here (21). However, this prior report did not include any analysis of heart failure or left ventricular function. Moreover, due to the smaller sample size of the initial cohort, the prior analysis was insufficiently powered to address potential interaction affects between Hp type and diabetes on cardiovascular end points.
All patients presenting to the intensive coronary care unit with acute myocardial infarction were eligible for entry into the study. The investigational review committee on human research approved the study protocol. Myocardial infarction was diagnosed based on the Joint European Society of Cardiology/American College of Cardiology criteria (22). Patients admitted >24 h from symptom onset were excluded.
Definition of diabetes.
Patients who had a clinical diagnosis of diabetes before enrollment into the study were classified as having diabetes. Patients were classified as having diabetes if the patient had been informed of the diagnosis by a physician before the admission and was taking oral antihyperglycemic agents, insulin, or receiving diet therapy.
Hp typing.
Hp phenotyping was performed on 10 e蘬 citrated plasma by polyacrylamide gel electrophoresis (11). We have previously established a 100% correspondence between the Hp phenotype as determined from serum by polyacrylamide gel electrophoresis and the Hp genotype as determined from DNA by PCR (23).
Study end points.
The primary end point of this study was death and the composite of death and heart failure occurring within 30 days of admission. Heart failure was diagnosed by the auscultation of rales over more than half of the lung field and pulmonary congestion on chest radiograph. Following hospital discharge, clinical end point information was acquired by reviewing the national death registry and by contacting each patient individually and independently reviewing the hospital course if the patient had been rehospitalized. The secondary end point was infarct size as determined by echocardiographic examination. This analysis was restricted to patients with no previous history of myocardial infarction.
Echocardiographic examination.
Assessment of left ventricular function by transthoracic echocardiography was performed on day 2eC3 of hospitalization in most patients or earlier if clinically indicated. The distribution of the Hp types and the incidence of major adverse clinical events of patients who did not undergo echocardiography were not different from those who did. Regional myocardial wall motion and left ventricular ejection fraction were determined from the echocardiogram by an observer blinded to the Hp type. For analysis of left ventricular function and wall motion abnormalities, we used the segmentation model according to the American Society of Echocardiography (24), with a higher index being associated with more severe contractile impairment.
Statistical analysis.
Baseline characteristics according to Hp type were compared by use of ANOVA for continuous variables and 2 test for categorical variables. Stepwise, multivariate logistic regression modeling was the primary statistical analysis used to determine the independent relationship between Hp type and other baseline characteristics to the primary end point. Multivariate linear regression analysis was used to determine the independent effect of Hp type on left ventricular function. Demographic and clinical variables that were considered to be possibly related to the primary end point or to left ventricular functional outcome, or both, were incorporated into the model, and the independent effect of Hp type was determined. Clinical variables for testing were chosen on the basis of their previously determined effect on 30-day mortality (25) and included age; sex; previous history of diabetes, hypertension, and myocardial infarction; smoking status; systolic blood pressure and heart rate upon admission; presence of ST-elevation infarction and anterior infarction; and use of reperfusion therapy.
Our analysis also focused on the possible interaction between Hp type and diabetes. The existence of an interaction between Hp type and diabetes was formally evaluated with the use of logistic regression models incorporating terms for the main effect of Hp type, the main effect of diabetes, and the interaction between Hp type and diabetes.
The influence of diabetes on Hp typeeCrelated differences in outcome was also assessed by a stratified analysis. In the stratified analysis, the predictive model developed for the entire study population was tested in subgroups of study patients defined by the presence or absence of diabetes. Differences were considered statistically significant at the two-sided P < 0.05 level. Statistical analyses were performed using the SPSS statistical software version 11.5.
ACKNOWLEDGMENTS
A.P.L. was supported by the Kennedy Leigh Charitable Trust, the Israel Science Foundation, the Binational Science Foundation, D Cure Diabetes Care in Israel, and the Russell Berrie Foundation.
FOOTNOTES
M.S. and D.A. contributed equally to this study.
A.P.L. has served on the advisory board of, holds stock in, and has received honoraria from Haptoguard.
AMI, acute myocardial infarction; Hp, haptoglobin
REFERENCES
Aronson D, Rayfield EJ, Chesebro JH: Mechanisms determining course and outcome of diabetic patients who have had acute myocardial infarction. Ann Intern Med126 :296 eC306,1997
Stone PH, Muller JE, Hartwell T, York BJ, Rutherford JD, Parker CB, Turi ZG, Strauss HW, Willerson JT, Robertson T, Braunwald E, Jaffe AS, the MILIS Study Group: The effect of diabetes mellitus on prognosis and serial left ventricular function after acute myocardial infarction: contribution of both coronary disease and diastolic left ventricular dysfunction to the adverse prognosis: the MILIS Study Group. J Am Coll Cardiol14 :49 eC57,1989
Holmes DR Jr, Berger PB, Hochman JS, Granger CB, Thompson TD, Califf RM, Vahanian A, Bates ER, Topol EJ: Cardiogenic shock in patients with acute ischemic syndromes with and without ST-segment elevation. Circulation100 :2067 eC2073,1999
Krolewski AS: Genetics of diabetic nephropathy: evidence for major and minor gene effects. Kidney Int55 :1582 eC1596,1999
Marre M, Jeunemaitre X, Gallois Y, Rodier M, Chatellier G, Sert C, Dusselier L, Kahal Z, Chaillous L, Halimi S, Muller A, Sackmann H, Bauduceau B, Bled F, Passa P, Alhenc-Gelas F: Contribution of genetic polymorphism in the renin-angiotensin system to the development of renal complications in insulin-dependent diabetes: Genetique de la Nephropathie Diabetique (GENEDIAB) study group. J Clin Invest99 :1585 eC1595,1997
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