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Usefulness of Plasma Tissue Inhibitors of Metalloproteinases asMarkers of Prognosis After Acute Myocardial Infarction

Dominic Kelly, MD*, Iain B. Squire, MD, Sohail Q. Khan, MD, Onkar Dhillon, MB,Hafid Narayan, MB, K.H. Ng, MB, Paulene Quinn, MPhil, Joan E. Davies, PhD,

and Leong L. Ng, MD

Alterations in the balance of matrix metalloproteinase to tissue inhibitor of metallopro-teinase (TIMP) are seen after acute myocardial infarction (AMI) and are associated withadverse left ventricular remodeling and prognosis in this setting. We aimed to investigatethe association between TIMP levels and the occurrence of major adverse cardiac events(MACEs) after AMI. We measured plasma TIMP-1, -2, and -4 levels in 1,313 patientspresenting with AMI. Subjects were followed over a median period of 520 days for theoccurrence of MACEs. Clinical risk was assessed using the Global Registry of AcuteCoronary Events (GRACE) score. All TIMP levels correlated with patient age and in-versely with estimated glomerular filtration rate (all p values <0.001). Levels were higherin women versus men (p <0.001) and in subjects with a history of diabetes (TIMP-1,p <0.001; TIMP-2, p � 0.002; TIMP-4, p <0.001) or hypertension (TIMP-1, p � 0.031;TIMP-2, p <0.001; TIMP-4, p <0.001). TIMP-1 and TIMP-4 were higher in subjects withprevious MI or angina (p <0.001). TIMP levels increased incrementally with quartiles ofGRACE score (p <0.001). All TIMPs showed univariate association with the occurrence ofMACEs (p <0.001). Areas under the receiver operator characteristic curve for predictionof MACE at 1 year were 0.61 for TIMP-1, 0.57 for TIMP-2, and 0.64 for TIMP-4.Combination of TIMPs with GRACE risk score revealed a greater area under the curvethan GRACE score alone (0.72 vs 0.69, p � 0.0015). On multivariable Cox proportionalhazards analysis, GRACE score (p <0.001) and plasma TIMPs (log TIMP-1, p � 0.017; logTIMP-2, p <0.001; log TIMP-4, p � 0.011) independently predicted MACEs. UsingKaplan-Meier analysis, the risk of MACEs increased incrementally with the number ofTIMPs above their respective median (p <0.001 for all comparisons, log-rank test). Inconclusion, higher plasma TIMP-1, -2, and -4 after AMI are associated with MACEs andprovide additional prognostic information to that obtained from GRACE clinical riskscores alone. Crown Copyright © 2010 Published by Elsevier Inc. All rights reserved. (Am

J Cardiol 2010;106:477–482)

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Assessment of prognosis is a core part of the manage-ent of acute myocardial infarction (AMI). Current prog-

ostic tools available to clinicians include assessment oflinical factors, which are incorporated into scoring systemsuch as the Global Registry of Acute Coronary EventsGRACE) risk score.1,2 Biochemical markers such aslasma natriuretic peptide concentrations are also useful androvide important prognostic information.3–6 Novel bio-hemical markers of prognosis may add additional informa-ion above and beyond that from those currently available.issue inhibitors of metalloproteinases (TIMPs) are low-olecular-weight proteins, the main biological action ofhich is to inhibit proteolytic activity of the matrix metal-

oproteinase (MMP) family of enzymes.7 Increased plasmaIMP levels have been demonstrated to be associated with

Department of Cardiovascular Sciences, University of Leicester, Leic-ster, United Kingdom. Manuscript received February 4, 2010; revisedanuscript received and accepted March 25, 2010.

*Corresponding author: Tel: 116-252-3132; fax: 116-252-3108.

ME-mail address: kelly.dominic@talk21.com (D. Kelly).

002-9149/10/$ – see front matter Crown Copyright © 2010 Published by Elsevioi:10.1016/j.amjcard.2010.03.060

dverse outcome in a variety of clinical settings includingardiovascular disease.8 On this background, the aim of theresent study was to investigate the association betweenirculating concentrations of several TIMPs (TIMP-1, -2,nd -4) and the occurrence of major adverse cardiac eventsMACEs) after AMI.

ethods

We conducted a prospective cohort study in 1,313 pa-ients with AMI admitted to the 2 coronary care units of theniversity Hospitals of Leicester NHS Trust (Leicester,nited Kingdom) from March 1, 2000 to April 31, 2007.he hospitals provide emergency and elective care for aatchment population of approximately 940,000. Diagnosisas based on presenting symptoms consistent with AMI

n conjunction with new dynamic electrocardiographichanges (ST-segment MI, n � 733, 55.8%) or ST-segment/-wave changes (non–ST-segment MI, n � 580, 44.2%)nd increase in plasma markers of myocardial necrosiscreatine kinase or troponin I to 2 times the upper limit oformal). Of the 733 patients presenting with ST-segment

I, 486 (66.3%) received thrombolytic therapy. No patients

er Inc. All rights reserved. www.ajconline.org

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ere treated with primary percutaneous coronary interven-ion, which was not available in our unit at that time. Wexcluded patients with coexisting illness likely to influenceIMP levels or prognosis, such as known malignancy orepsis. Venous blood samples were taken in the convales-ent phase of the acute coronary syndrome, within 4 daysfter admission, for determination of plasma levels ofIMP-1, TIMP-2, and TIMP-4. After 15 minutes of bed rest0 ml of blood was collected into tubes containing ethyl-nediaminetetra-acetic acid and aprotinin. All plasma wastored at �70°C until assayed in a single batch, blind toatient details. For each patient, the GRACE score, a mea-urement of risk of adverse outcome based on clinical vari-bles1 was calculated. Factors included in the GRACE scorere patient age, heart rate, and systolic blood pressure atresentation, creatinine, Killip class, cardiac arrest at ad-ission, ST-segment deviation, and increase of cardiac en-

ymes. The predefined primary outcome measurement washe composite of all-cause mortality, recurrent nonfatal MI,r heart failure episode (MACEs) during follow-up. Heartailure episode was defined as an unplanned hospital admis-ion (�12 hours) for which the primary reason was clinicaleart failure requiring high-dose diuretic (furosemide �40g intravenously), intravenous nitrate, or inotropic support.econdary outcomes were the individual components of

he primary outcome. Clinical end points were identifiedhrough the hospital patient-tracking system, with review of

able 1dmission demographic features, medications at discharge, and differenceon–ST-elevation myocardial infarction

ariable

ge (years)enedical history

DiabetesHypertensionIschemic heart diseaseLeft ventricular failureCurrent smoker

ndex admissionAnterior territoryThrombolysisPeak creatine kinase (IU/L, normal range 0–200)Troponin I (mg/L)Estimated glomerular filtration rate (ml/min)Global Registry of Acute Coronary Events scoredmission Killip classIIIIIIIVedications

Aspirin� BlockerAngiotensin-converting enzyme inhibitor/angiotensin receptor blockerStatinFurosemide

NSTEMI � non–ST-elevation myocardial infarction; STEMI � ST-ele* Comparison of baseline factors between STEMI and NSTEMI.

edical records for each end point. Checks were made by T

elephone contact with all surviving patients on a singleccasion at the end of the study to ensure complete capturef all events. The local research ethics review committeepproved the study and all patients gave written consent toarticipation. The conduct of the study was in keeping withhe Declaration of Helsinki.

The TIMP assay used was based on a noncompetitivessay. All antibodies were obtained from R&D SystemsAbingdon, United Kingdom). Assays for TIMPs were con-tructed using specific monoclonal mouse antibodies forapturing the TIMPs, coating 200 ng/well of the respectivepecific monoclonal antibody in wells of enzyme-linkedmmunosorbent assay plates. After overnight incubation,lates were washed and then blocked with 10% fetal calferum. Samples and standards were pipetted into the wellssing dilution series of recombinant standards (TIMP-1 400g/well downward, TIMP-2 200 pg/well downward, TIMP-400 pg/well downward). After overnight incubation, platesere washed, and then biotinylated goat polyclonal antibod-

es specific for each TIMP were pipetted into the wells (50g/well). Plates were washed after 2-hour incubation atoom temperature. Detection was with methyl-acridiniumster–labeled streptavidin on an MLX plate luminometerDynex Technologies, Ltd., Worthing, United Kingdom)sing sequential injections of hydrogen peroxide in nitriccid followed 4 seconds later by sodium hydroxide in cetyl-mmonium bromide. There was no cross-reactivity between

mographic factors in patients with ST-elevation versus

ll Patients STEMI NSTEMI p Value*� 1,313) (n � 733) (n � 580)

(24–97) 64 (24–95) 70 (37–97) �0.001(72.2%) 550 (75.0%) 398 (68.6%) 0.008

(23.5%) 142 (19.4%) 167 (28.8%) �0.001(49.0%) 298 (40.7%) 346 (59.7%) �0.001(34.0%) 176 (24.0%) 271 (46.7%) �0.001(3.9%) 38 (5.2%) 13 (2.2%) 0.006(46.4%) 453 (61.8%) 156 (26.9%) �0.001

(36.6%) 286 (39.0%) 194 (33.4%) 0.033(37.0%) 486 (66.3%) — —(4.5–9,523) 939 (4.5–9,523) 243 (35–7,264) �0.001(0.06–150) 11.0 (0.06–150.0) 2.0 (0.06–67.0) �0.001(12.0–184.3) 68.6 (17.8–177.3) 62.6 (12.0–184.3) �0.001(31–299) 155 (31–299) 146 (55–284) 0.001

(52.7%) 328 (44.7%) 364 (62.8%) —(30.7%) 270 (36.8%) 139 (24.0%) —(9.7%) 53 (7.2%) 74 (12.8%) —(0.3%) 2 (0.3%) 2 (0.3%) —

(86.0%) 662 (90.3%) 467 (80.5%) �0.001(79.8%) 609 (83.1%) 439 (75.7%) �0.001(78.8%) 585 (79.8%) 449 (77.4%) 0.292(82.9%) 598 (81.6%) 491 (84.7%) 0.142(29.2%) 210 (28.6%) 174 (30.0%) 0.604

myocardial infarction.

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479Coronary Artery Disease/TIMPs After Acute Myocardial Infarction

For all variables with non-Gaussian distribution (TIMPs,reatine kinase, troponin I), log-transformed values were

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actor TIMP-1

ge (years) r � 0.287stimated glomerular filtration rate (ml/min) r � �0.270reatine kinase (IU/L) r � 0.042roponin (mg/L) r � 0.069enderMen 222.0 (0.3–826Women 247.5 (5.2–963iabetesYes 256.2 (0.3–963No 219.4 (0.3–720ypertensionYes 232.4 (5.2–826No 221.4 (0.3–963

schemic heart diseaseYes 252.0 (0.3–963No 215.3 (0.3–720eft ventricular failureYes 274.7 (80.8–61No 223.5 (0.3–963nterior territoryYes 230.7 (0.3–720No 222.5 (5.2–963hrombolysis (ST-elevation myocardial infarction only)Yes 235.4 (35.8–96No 227.9 (0.3–720mokerYes 223.6 (0.3–664No 226.9 (0.31–96T-elevation myocardial infarction 233.4 (0.3–963on–ST-elevation myocardial infarction 217.4 (5.2–826

* For correlation coefficients for continuous variables and for between-

sed in analyses. Associations of TIMP levels with categor- w

cal variables were assessed using paired t test or Mann-hitney U test for non-normally distributed variables and

43

uartile

ACE risk score (quartiles).

p Value* TIMP-2 p Value* TIMP-4 p Value*

�0.001 r � 0.271 �0.001 r � 0.449 �0.001�0.001 r � �0.237 �0.001 r � �0.366 �0.001

0.248 r � 0.046 0.201 r � �0.040 0.2660.041 r � 0.066 0.049 r � �0.074 0.028

�0.001 88.2 (33.1–361.1) �0.001 4.2 (1.1–67.4) �0.00194.8 (94.8–465.3) 5.7 (1.0–83.8)

�0.001 93.3 (47.0–164.0) 0.002 5.3 (1.2–52.5) �0.00188.6 (33.1–465.3) 4.3 (1.0–83.8)

0.031 92.7 (33.1–361.2) �0.001 4.9 (1.3–67.4) �0.00186.5 (33.6–465.3) 4.2 (1.0–83.8)

�0.001 90.7 (33.1–465.2) 0.061 5.6 (1.4–61.2) �0.00189.1 (33.6–325.2) 4.1 (1.0–83.8)

0.012 83.7 (59.2–211.3) 0.138 5.14 (2.2–17.5) 0.07989.7 (33.1–465.3) 4.5 (1.01–83.8)

0.227 89.0 (33.1–313.8) 0.564 4.6 (1.2–83.8) 0.89489.6 (41.7–465.3) 4.5 (1.0–65.4)

0.200 89.1 (33.6–361.1) 0.117 3.9 (1.2–83.8) 0.11393.1 (52.7–221.6) 4.4 (1.0–65.5)

0.518 86.6 (33.1–211.3) �0.001 3.8 (1.1–65.4) �0.00192.9 (47.0–465.3) 5.0 (1.0–83.8)

�0.001 90.4 (33.6–361.2) 0.082 4.2 (1.0–83.8) �0.00188.7 (33.1–465.3) 5.1 (1.1–60.5)

omparison for categorical variables.

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480 The American Journal of Cardiology (www.ajconline.org)

ient. Differences in TIMPs between quartiles of GRACEisk score were compared using between-group analysis ofariance. Factors with univariate association with each endoint at a significance level of a p value �0.1 were enterednto multivariable Cox proportional hazards models. Forach TIMP, the strength of association with end points isxpressed as hazard ratio (HR) per log-transformed unitncrease in plasma concentration of that TIMP. When con-idering the primary end point of MACEs, we assessed timeo first event. Median values of each TIMP were calculatedor the entire population and used as cut-off points to predictdverse outcome using Kaplan-Meier assessment; we com-ared outcome between groups with 0, 1, 2, or 3 TIMPsbove their respective median. Receiver operator characteristicurves were constructed for the predictive ability of each of ourarkers and for GRACE risk score. Comparison between

-statistics of receiver operator characteristic curves was per-ormed using the method of DeLong et al.9 For all analyses,

p value �0.05 was regarded statistically significant and-sided tests were used where appropriate. Statistical analysesere carried out using SPSS 14 (SPSS, Inc., Chicago, Illinois)

nd Analyse-it (Analyse-it software, Ltd., Leeds, United King-om) for Excel. The authors had full access to the data, acceptesponsibility for their validity, and have read and agreed to theeport as submitted.

esults

Admission demographic features, medications at dis-harge, and differences in demographic factors betweenhose admitted with ST-elevation versus non–ST-elevation

I of the study population are listed in Table 1. Sevenundred thirty-three (55.8%) presented with ST-segmentI, of whom 484 (66%) received thrombolytic therapy. No

atient received primary percutaneous revascularization.ollow-up was obtained in all 1,313 patients over a medianf 520 days (range 1 to 2,825). For patients alive at the end

able 3ox proportional hazards analysis for primary outcome of major adverse

ale genderedical history

Ischemic heart diseaseHypertensionDiabetesLeft ventricular failureSmoking

ndex admissionAnterior myocardial infarctionST-elevation myocardial infarctionTroponinAngiotensin-converting enzyme inhibitor/angiotensin receptor blocker� blockerGlobal Registry of Acute Coronary Events scoreog-transformed values of tissue inhibitors of metalloproteinase124

f the study, minimum follow-up was 125 days. M

Figure 1 shows the incremental increase in TIMP-1 levelsivided by clinical risk as assessed by GRACE risk scorequartiles) at admission (p �0.001, analysis of variance). Sim-lar changes in plasma concentrations of TIMP-2 and TIMP-4ere also seen (all p values �0.001, analysis of variance).Factors associated with individual plasma TIMP levels

re listed in Table 2. All TIMPs were directly correlated toge and inversely to estimated glomerular filtration rate. AllIMPs were lower in men compared to women and wereigher in subjects with previous diabetes mellitus or hyper-ension. TIMP-1 and TIMP-4 were higher in subjects withrevious ischemic heart disease. TIMP-2 and TIMP-4 wereower in smokers. There was weak correlation betweenevels of each TIMP and troponin I, but not creatine kinase.IMP-1 was higher and TIMP-4 lower in ST-segment MIompared to non–ST-segment MI. Factors with univari-ble association with each TIMP were entered into aultivariable regression model for prediction of plasmaIMP concentrations. Factors demonstrating an independentssociation with TIMP-1 were age (p �0.001), estimated glo-erular filtration rate (p �0.001), history of diabetes

p �0.001), and ST-segment MI (p �0.001). Factors demon-trating an independent association with TIMP-2 were agep �0.001), estimated glomerular filtration rate (p �0.001),nd nonsmoking history (p � 0.032). Factors with an indepen-ent association with TIMP-4 were age (p �0.001) and pre-ious ischemic heart disease (p � 0.001).

Table 3 presents results of Cox proportional hazardsnalysis for the primary outcome of MACEs. Each TIMPas entered into the model individually.On multivariable analysis, log TIMP-1 (HR 2.59, 95%

onfidence interval [CI] 1.34 to 4.87, p � 0.003), logIMP-2 (HR 6.00, 95% CI 2.62 to 13.71, p �0.001), and

og TIMP-4 (HR 2.12, 95% CI 1.36 to 3.30, p � 0.001)etained an independent association with occurrence of

ACEs. Other factors retaining an association with

events

Univariable Analysis Multivariable Analysis

HR (95% CI) p Value HR (95% CI) p Value

.72 (0.58–0.90) 0.003 1.06 (0.82–1.35) 0.672

.78 (1.45–2.18) �0.001 1.23 (0.97–1.56) 0.088

.64 (1.34–2.02) �0.001 1.47 (1.11–1.87) 0.001

.64 (1.32–2.04) �0.001 1.27 (0.99–1.64) 0.060

.50 (0.96–2.33) 0.072 —

.73 (0.59–0.90) 0.003 0.90 (0.71–1.14) 0.381

.08 (0.87–1.32) 0.487 —

.90 (0.73–1.12) 0.344 —

.00 (1.00–1.01) 0.594 —

.73 (0.58–0.91) 0.005 0.70 (0.55–0.90) 0.006

.53 (0.43–0.66) �0.001 0.77 (0.60–1.00) 0.046

.02 (1.01–1.02) �0.001 1.01 (1.01–1.02) �0.001

.11 (4.70–14.00) �0.001 2.59 (1.34–4.87) 0.003

.20 (10.4–47.35) �0.001 6.00 (2.62–13.71) �0.001

.95 (2.85–5.48) �0.001 2.12 (1.36–3.30) 0.001

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481Coronary Artery Disease/TIMPs After Acute Myocardial Infarction

.11 to 1.87, p � 0.005), angiotensin-converting enzymenhibitor/angiotensin receptor blocker (HR 0.70, 95% CI.55 to 0.90, p � 0.006) or �-blocker (HR 0.77, 95% CI.60 to 1.00, p � 0.046) use at discharge, and GRACE riskcore (HR 1.01 per unit increase, 95% CI 1.01 to 1.02, p �.003). Receiver operator characteristic areas under the curveor primary outcome at 1 year were 0.61 (95% CI 0.57 to 0.64,�0.001) for TIMP-1, 0.57 (95% CI 0.54 to 0.61, p �0.001)

or TIMP-2, and 0.64 (95% CI 0.60 to 0.67, p �0.001) forIMP-4. Area under the curve for GRACE risk score was 0.69

95% CI 0.66 to 0.73, p �0.001). A logistic model combiningll 3 TIMP markers plus GRACE risk score revealed a greaterrea under the curve than GRACE alone of 0.72 (95% CI 0.68o 0.75, p � 0.015 for comparison).

Figure 2 shows Kaplan-Meier survival curves stratifiedy 0 TIMP, 1 TIMP, 2 TIMPs, or all 3 TIMPs above theespective median value. Patient event-free survival wasnversely associated with number of TIMPs above the re-pective median (p �0.001 for all comparisons). Event-freeurvival was almost 90% if all TIMPs were below theedian values but was �40% in those subjects with allIMPs above the median.

Assessment of association between TIMPs and second-ry outcomes was made. On multivariable Cox regressionnalysis, factors showing independent association with all-ause mortality were previous ischemic heart disease (HR.72, 95% CI 1.22 to 2.42, p � 0.002), GRACE score (HR.02 per unit increase, 95% CI 1.01 to 1.02, p � 0.042), andngiotensin-converting enzyme inhibitor/angiotensin recep-or blocker (HR 0.54, 95% CI 0.38 to 0.76, p �0.001) or-blocker (HR 0.62, 95% CI 0.44 to 0.87, p � 0.006) use atischarge. Log TIMP-1 (HR 7.01 per unit increase, 95% CI.75 to 17.90, p �0.001) and TIMP-4 (HR 3.48 per unitncrease, 95% CI 1.95 to 6.21, p �0.001) retained an inde-endent association, whereas TIMP-2 did not.

The only factor showing independent association with

igure 2. Kaplan-Meier survival curves stratified by all 3 TIMPs aboveedian value (purple line), 2 TIMPs above median value (gray line), 1IMP above median value (green line), and blue TIMPs below medianalue (blue line).

ecurrent infarction was TIMP-2 (HR 6.13 per unit increase, i

5% CI 1.57 to 23.89, p � 0.009). Plasma levels of TIMP-1HR 3.98 per unit increase, 95% CI 1.24 to 12.77, p � 0.02),IMP-2 (HR 7.08 per unit increase, 95% CI 1.76 to 28.48,� 0.006), and TIMP-4 (HR 2.89 per unit increase, 95% CI.34 to 6.26, p � 0.007) showed an independent associationith heart failure episode, together with history of hyper-

ension (HR 1.94, 95% CI 1.23 to 3.04, p � 0.004),-blocker use at discharge (HR 0.63, 95% CI 0.41 to 0.98,� 0.04), and GRACE risk score at admission (HR 1.02

er unit increase, 95% CI 1.01 to 1.02, p �0.001).

iscussion

In our large population drawn from routine clinical prac-ice, plasma concentrations of 3 individual TIMPs showedn association with adverse outcomes. Consideration oflasma levels of multiple TIMPs provided incrementalrognostic information. We observed a correlation betweenIMPs and clinical risk as assessed using the GRACE riskcore. Our data add to the growing body of evidence support-ng the pathophysiologic and prognostic relevance after AMIf MMPs and their inhibitors. We previously reported associ-tions with left ventricular remodeling after AMI of plasmaMP-9,10 MMP-3,11 and TIMP-1,12 and with adverse events,

f higher plasma concentrations of MMP-9 and TIMP-1.12 Theresent report confirms this relation for TIMP-1 in a largeropulation and extends the observation to TIMP-2 andIMP-4. Further, we report the cumulative prognostic value ofonsideration of multiple TIMP concentrations and an associ-tion with recurrent infarction for plasma TIMP-2.

Given the pathophysiologic activity of the TIMPs and ofheir main substrates, the MMPs, our novel observations areiologically plausible. The MMPs are involved in numeroushysiologic and pathologic processes, being largely underhe control of the TIMPs and are central to the maintenancef normal myocardial structure and function. Altered activ-ty of the metalloproteinase system is involved in coronarylaque formation, plaque rupture leading to MI,13 and inubsequent remodeling of the left ventricle leading to pro-ressive heart failure.14 On this background, our observedssociation between plasma TIMP concentrations after AMInd a variety of important cardiovascular outcomes is plau-ible. Higher circulating TIMPs after AMI are likely toeflect a response to altered MMP activity, itself associatedith adverse prognosis after AMI.12,14 In this context, in-

reased TIMP production may represent evidence of a com-ensatory response to increased MMP activity and, hence,ay be thought of as a surrogate marker of severity of

esidual left ventricular function.Although the TIMPs have similar basic structures, they

xhibit distinctive biochemical properties and expressionatterns.15 Interestingly, our observations suggest that theIMPs show a differential association with individual out-omes. TIMP-1 and TIMP-4 are associated with mortality,IMP-2 is associated with MI, and all TIMPs are associatedith heart failure episode. This would suggest that thereay be different influences on upregulation and release of

ndividual TIMPs and that an individual TIMP associationith outcome may represent different pathophysiologicechanisms. Upregulation of cardiac TIMP-1 and TIMP-2

s associated with degree of myocardial collagen deposition

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482 The American Journal of Cardiology (www.ajconline.org)

nd interstitial fibrosis, suggesting that an imbalance ofIMP/MMP may be contribute to the risk of arrhythmo-enic events.16 In support of this Elmas et al17 showedncreased TIMP-1 in subjects with ventricular fibrillationfter AMI. Our finding of an association between TIMP-2nd recurrent MI is also of clinical interest. MMP/TIMP inter-ction is involved in the formation of coronary plaques and inlaque rupture leading to AMI. In this sense increased TIMP-2evels may be a reflection of degree of plaque instability inhose subjects at risk of recurrent infarction. In addition,IMP-2 is required as a cofactor in the process leading toctivation of pro-MMP-2,18 hence, increasing downstream lev-ls of the active MMP. TIMPs also have additional activityuch as cell growth promotion19 and antiapoptotic and antian-rogenic activities,20 which appear independent of their met-lloproteinase inhibition activity. The mechanism by whichIMPs exert their effects independent of metalloproteinase

nhibition is, however, to date poorly described.Manipulation of the metalloproteinase system may be a

otential therapeutic target after MI. To date, human studiesf metalloproteinase inhibition have been lacking. The re-ent Prevention of Myocardial Infarction Early RemodelingPREMIER) study21 of the metalloproteinase inhibitor (PG-16800) in patients with ST-segment AMI failed to showny benefits in left ventricular remodeling or adverse out-ome; however, further studies are warranted.

Our study does have some limitations. We performed aingle-center study and as such we cannot with confidencextrapolate our data to other populations. We present data frompopulation that may include subjects with unidentified co-orbidity affecting TIMP levels. It may be suggested that

ncreased TIMP levels are a reflection of degree of renalmpairment and, hence, decreased clearance; however correla-ion of estimated glomerular filtration rate with TIMP levelsas relatively weak. In addition, at the time of the study ournit did not provide primary percutaneous coronary interven-ion and our study should be repeated in such a population. Wecknowledge that differences in pharmacologic therapy mayias results especially because our cohort was collected over7-year period. However, before admission few subjectsere receiving cardiovascular medications and therapy atischarge was relatively uniform within infarct groups. Were aware that some of the relations seen between TIMPevels and clinical features are relatively weak; however,his is commonly seen in such “real-life,” studies. Our datao not allow us to identify a causal relation between TIMPsnd clinical end point. We recommend that further studiesnvestigate the pathophysiologic link between TIMPs anddverse prognosis after AMI.

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