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Prognostic value of plasma fibrinogen concentration in patients with unstable angina and non-Q-wave myocardial infarction (TIMI IIIB Trial)
Prognostic Value of Plasma Fibrinogen Concentration in Patients With Unstable Angina and Non-Q-Wave Myocardial Infarction (TIMI IIIB Trial) Richard C. Becker, MD, Christopher P. Cannon, MD, Edwin G. Bovill, MD, Russell P. Tracy, PhD, Bruce Thompson, PhD, Gene11 L. Knatterud, PhD, Amy Randall, MD, for the TIMI III Investigators and Eugene Braunwald, Inflammation may play an important role in acute coronary syndromes. We studied the prognostic value of fibrinogen, an acute-phase protein directly involved in thrombotic processes, measured serially in 1,473 patients with unstable angina and non-Q-wave myocardial infarction participating in the Thrombolysis in Myocardial Infarction IIIB trial. Overall, no association was found between baseline (pretreatment) fibrinogen and in-hospital (5 10 days) myocardial infarction (p=O.70) and death (p=O&); however, patients with spontaneous ischemia (p=O.O04) and the combined unsatisfactory outcome of death, myocardial infarction, and spon-
taneous ischemia (p=O.O03) had higher fibrinogen concentrations than those without these events. This association was confined to patients with unstable angina. A baseline fibrinogen concentration 2300 mg/dl was associated with a modest trend toward an increased risk of death, myocardial infarction, or spontaneous ischemia (odds ratio 1.6 1,95% confidence interval 1.02 to 2.52; p=O.O4). Elevation of fibrinogen, a readily measurable acute-phase protein, at the time of hospital admission is associated with coronary ischemic events and a poor clinical outcome in patients with unstable angina. (Am J Cardiol 1996;78: 142- 147)
istologic studies have shown that atheroscleH rotic plaques contain foci of macrophages, monocytes, and activated lymphocytes.‘-’ The cy-
bolysis in Myocardial Infarction (TIM1 IIIB j trial, we conducted a prospective study to examine the association between fibrinogen concentrations and clinical events.
tokine secretory capacity of monocytes expressing tumor necrosis factor, interferon-y, interleukin-1, interleukin-6, and intracellular adhesion molecules is also increased.4%5Markers of biologic inflammation could conceivably facilitate the premorbid diagnosis of atherosclerosis, predict clinical events, and potentiate the development of new therapies. In a recent study,6 the acute-phase reactants Creactive protein and amyloid A protein were elevated in most patients with unstable angina. The patients with elevated levels of these proteins had a less favorable clinical course than did those with normal levels. Fibrinogen, another acute-phase protein, has been identified in several large-scale epidemiologic studies as an independent predictor of thrombotic cardiovascular events, and, because it is a pivotal component of the coagulation cascade, it may be more directly involved in the clinical expression of atherosclerotic coronary artery disease than are nonspecific markers of inflammation.7 Because fibrinogen was measured at serial time points in the ThromFrom the Cardiovascular Thrombosis Research Center, Uni,\iersity of Massachusetts Medical School, Worcester, Massachusetts; the LabUniveroratoy for Biochemistry Research, De artment of Pathology, sibi of Vermont Medical School, Coic L ester, Vermont; the Maryland Medical Research Institute, Baltimore, Mar$and; and the Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts. Manuscript recei\/ed August 10, 1995; revised manuscript received and acceptedJanuary 25, 1996. Address for reprints: Richard C. Becker, MD, Department of Medicine, University of Massachusetts Medical Center, 5.5 Loke Avenue North, Worcester, Massachusetts.
142
0 1996 by Excerpta Medico, All rights reserved.
Inc.
METHODS
The TIM1 III trial design has been reported previously.’ In brief, to be eligible for study participation, a patient was required to have experienced chest pain at rest presumed to be ischemic in origin, lasting 2.5 minutes but not >6 hours. Symptoms must have occurred within 24 hours of enrollment, accompanied by objective evidence of ischemic heart disease. The latter was defined as ( 1) new or presumably new electrocardiographic evidence of ischemia in at least 2 contiguous leads ( z-O.1 mV ST-segment elevation lasting <30 minutes, or transient/persistent ST-segment depression or T-wave inversion during an episode of rest pain within the prior 7 days ) , or (2 ) documented coronary artery disease (a history of previous myocardial infarction [MI], ~70% luminal diameter stenosis on a prior coronary angiogram, or an abnormal exercise thallium scan). Patients were excluded if they had a treatable cause of unstable angina, had experienced MI within the preceding 21 days, had undergone coronary angioplasty within 6 months, or had coronary bypass grafting at any time. Initial management: All patients received a full complement of anti-ischemic medication, including a ,8 blocker, calcium channel antagonist, and a nitrate preparation. Patients received intravenous heparin in sufficient quantity to maintain the activated partial thromboplastin time at 1.5 to 2.0 times laboratory control values. Aspirin, 325 mglday, was begun on 0002.9 149/96/s 15 .OO PII 50002.9149(96)00247-O
the second hospital day and continued for at least 1 year. Treatment/strategy: Patients were assigned randomly, using a 2 x 2 factorial design, to treatment with tissue plasminogen activator (tPA; Activase@ Genentech, South San Francisco, California) or placebo. The total dose of tPA was 0.8 mg/kg (maximal dose 80 mg) given intravenously over 90 minutes (one third of the total dose was given as a bolus, not to exceed 20 mg) . Patients were also assigned to either an early invasive or an early conservative strategy. Definitions: Spontaneous ischemia was defined as recurrent chest discomfort at rest, accompanied by ST-segment or T-wave changes on a 12-lead electrocardiogram. Blood was sampled for creatine kinase (CK) and CK-MB at 0, 4, 12, 24, 48, and 72 hours after randomization, and every 8 hours for a total of 24 hours when pain recurred. A CK-MB above the normal range or a total CK twice normal on the baseline, 4-hour, or 12-hour sample was considered evidence of infarction. Reinfarction was defined as CK or CK-MB elevation greater than the upper limit of normal. All end points were confirmed by a separate mortality and morbidity classification committee. Measurements: Blood was drawn into specially prepared collection tubes containing a final concentration of 4.5 mmol/L ethylenediaminetetraacetic acid, 50 pmol/L D-Phe-Pro-Arg chloromethyl ketone (PPACK), and 150 KIU/ml aprotinin. Fibrinogen levels were determined using the method of Clauss’ as modified for a semiautomated fibrometer (BBL, Hunt Valley, Maryland). Studies in our core laboratory indicated that a 45minute preincubation of the test plasma at 37°C was required to remove the antithrombin effect of active PPACK, lo thus allowing accurate estimation of the fibrinogen levels from the clotting rate. Heparin at plasma concentrations of up to 10 U/ml has no effect on this assay.” Statistical analysis: The mean, SD, and median of fibrinogen values were calculated for the 6 time points representing the protocol times for blood collection. Comparison of the pretreatment fibrinogen levels with post-treatment levels was accomplished using paired t tests. Comparison of fibrinogen levels for patients with and without clinical events was performed using Wilcoxon rank sums. When comparing fibrinogen levels collected after study entry (e.g., at 96 hours), patients with clinical events before the collection time were excluded from the comparison. Because of the large number of statistical hypotheses tested in TIM1 IIIB, p values
TABLE I Plasma Fibrinogen Sompling
I
Values at Six Predetermined Times (TIMI IllB (n = 1,473)
Time
12h 24 h 48 h 96 h
1.304
11264 1,104 versus baseline;
TIMI = Thrombolysis
’ p = 0.04
in Myocardiol
(mg/dl) I
1,339 1,329 1,314
Pretreatment 50 min
* p ~0.001
Fibrinogen
Number of Patients
Mean
SD
293 269* 265* 283’ 320* 372*
a2 74 a3 86 97 113
258 276 307 360
versus baseline.
Infarction
trial.
24 hours. This decrease was particularly evident in patients who received tPA. Beyond 24 hours, fibrinogen levels increased, surpassing pretreatment values in all groups. The greatest increase was observed in patients with non-Q-wave MI (Figure 1). The association between baseline fibrinogen concentration and in-hospital ( I 10 days) clinical events is outlined in Table II. No association was found for MI (p=O.70), death (p=O.64), or the combined outcome of death or MI (p=O.56); however, patients with spontaneous ischemia (p=O.O04) and the combined unsatisfactory outcome of death, MI, or spontaneous ischemia (p=O.O03) had higher baseline fibrinogen values than those without these events. The association between baseline fibrinogen level and inhospital ischemic events was confined to patients with a diagnosis of unstable angina (Table III). By logistic regression analysis, a baseline fibrinogen level >300 mg/dl was associated with a trend toward an increased risk of death, MI, or spontaneous ischemia (odds ratio 1.61, 95% confidence interval 1.02 to 2.52; p=O.O4). When adjusted for other covariables, including age, sex, prior infarction, tPA treatment, strategy, ST-segment deviation, and CK elevation, the association between baseline fibrinogen and clinical outcome was less striking (odds ratio 1.50, 95% confidence interval 0.95 to 2.38; p=O.O8). The association between baseline and 96-hour fibrinogen levels and clinical events at 42 days is shown in Table IV. A trend toward increased fibrinogen levels at baseline and spontaneous ischemia (p=O.O2) and the combined outcome of MI, death, or spontaneous ischemia (p=O.O2) was observed. There was no association between 96-hour (peak) fibrinogen and 42-day clinical events in any of the patient groups.
DISCUSSION
Previous studies have reported increased levels of acute-phase proteins in patients with coronary artery disease, l2 unstable angina,6’L3’14and MI,15 but most of these studies did not specifically investigate their prognostic importance. The results of our study, the RESULTS Plasma fibrinogen concentrations for the 6 sam- largest to date of patients with myocardial ischemia pling points are listed in Table I. There was an initial at rest, confirm that an elevated baseline fibrinogen decrease in fibrinogen levels at 50 minutes that per- level portends an increased risk of in-hospital corosisted, although to a lesser degree, for the first 12 to nary ischernic events. CORONARY
ARTERY DISEASE/PLASMA
FIBRINOGEN AFTER INFARCTION
143
OIPA I Placebo ohservativeStrategy slnvasive Strategy i
600-
500.
Fibrinogen (mgldl)
Fibrinogen (mgldl)
Baseline 50th. 12Hr. 24Hr. 48Hr. 96Hr.
Baseline 50Mm. 12Hr. 24Hr. 48Hr. 96Hr.
Unstable Angina
Non-Q Wave MI
FIGURE 1. Mean fibrinogen values at the 6 sampling times according to treatment (tissue plasminogen activator WA1 vs placebo), strategy (invasive vs conservative), and diagnosis (unstable angina vs non-Q-wave myocardial infarction [MI]).A decrease was observed within 50 minutes of enrollment that was most pronounced in patients given tPA. Levels increased after 24 hours and exceeded baseline values by 96 hours in all patient groups.
TABLE II Baseline
Plasma
Fibrinogen
Values
According
to the
Occurrence
of Clinical Pretreatment
End
Point
Myocardial
n
N infarction
End
Points
at
Fibrinogen
10
Days
(TIMI
IIIB)
(N
=
1,473)
(mg/dl)
Mean
SD
Median
p Value*
301
293
97 82
290 282
0.70
0.64
(MI)
73
YES No
63
1,400
1,263
Death 1,452
1,316
297 293
52 83
299 282
86 1.387
68 1,258
301
94 82
291
293
281
0.56
305 290
82 82
296 280
0.004
305 290
81
82
296 280
0.003
21
Yes No Death
or MI
Yes No Spontaneous
ischemia 310
Yes
281
1,163
No Ml,
10
death,
or spontaneous
1,045
ischemia
322
Yes
286
1,151
No * Wilcoxon Abbreviation
[rank
1,040
sums).
OS in Table
I
A number of prospective epidemiologic studies have shown a strong association between elevated plasma fibrinogen levels and the risk of ischemic heart disease and stroke.‘6*17In the European Concerted Action on Thrombosis and Disabilities (ECAT) Angina Pectoris Study, l8 fibrinogen level was an independent predictor of subsequent MI and 144
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sudden death. Patients with and without events had fibrinogen values of 328 -t 0.74 and 300 f: 0.71 mg/ dl, respectively. Our findings were similar, and suggest that a fibrinogen concentration >300 mg/dl in the setting of either accelerated angina or angina at rest is associated with an increased risk of coronary events. Because fibrinogen is an essential component JULY
15,
1996
TABLE III Baseline
Plasma
Fibrinogen
Values
According
to the Occurrence
of Clinical
Pretreatment Patients With End Point Myocardial infarction (MI) Yes No Death Yes No Death or MI Yf?S No Spontaneous ischemia Yes No MI, death, or spontaneous ischemia Yes No + Wilcoxon Abbreviation
(rank
Angina
Values According on Day 4 (n = 1,463)
Myocardial infarction (MI) Yes No Death Yes No Death or MI Yes No Spontaneous ischemia Yes NO Ml, death, or spontaneous ix :hemia Yes No (rank
Non-Q-Wave
MI (N = 477)
N
n
Mean
SD
Median
p Value*
N
n
Mean
SD
Median
53 940
46 855
309 295
107 84
281 286
0.61
20 A57
17 405
279 290
61 76
296 276
0.89
8 985
4 897
292 295
68 86
284 286
13 464
6
0.99
Al6
300 289
A6 76
299 277
0.49
57 936
A8 853
307 295
105 84
281 286
0.65
29 448
20 402
286 289
59 76
296 276
0.71
210 783
193 708
311 291
85 85
302 280
0.001
99 378
87 335
290 289
73 76
288 274
0.70
215 778
196 705
311 291
85 85
302 280
0.001
106 371
88 333
291 289
73 76
289 274
0.61
to the Occurrence
Patients With End Point
Wilcoxon
Patients With
(N = 993)
of Clinical
pValue*
End Points at 42 Days (TIMI IIIB): Pretreatment
l
(mg/dl)
I.
TABLE IV Fibrinogen
Abbreviation
Fibrinogen
sums).
OS in Table
All Patients Alive
Unstable
End Points at 10 Days (TIMI IIIB)
Unstable
Angina
(N = 1,473)
Fibrinogen
(mg/dl)
Patients With
Non-Q-Wave
N
n
Mean
SD
Median
pValue
0.88
87 1,376
64 1,037
377 373
121 113
384 358
o.i2*
301 281
16
0.30*
1,441
434 372
178 112
380 360
0.25*
90 82
282 282
100
72
0.95*
1,363
1,029
382 373
122 113
382 358
O.d8*
302 291
81 83
290 280
0.02*
333 1,130
252 849
381 371
112 114
381 356
0.11’
302 291
80 83
290 280
0.02*
341 1,122
259 842
381 371
112 114
378 356
0.1
N
n
Mean
SD
Median
90 1,383
79 1,247
297 293
94 82
276 282
32 1,441
18 1,308
306 293
58 83
110 1,363
89 1,237
297 293
337 1,136
306 1,020
351 1,122
313 1,013
p Value
22
1,085
Ml (N = 477)
1
sums).
as in Table
I
in normal hemostasis, it is not unexpected that perturbations in this system could be linked to pathologic thrombosis.‘9-20 New fibrinogen is highly thrombogenic, and the thrombi formed typically have a tight, rigid, and space-filling fibrin network.*’ Furthermore, hydrophobic, atheromatous lipid surfaces, particularly those rich in cholesterol esters, are predisposed to thrombosis by virtue of their inherent capacity to bind functional fibrinogen.22 The hepatic synthesis of fibrinogen, as well as of other acute-phase proteins including C-reactive protein, amyloid A protein, haptoglobin, ceruloplasmin, and cu,-antitrypsin, is regulated primarily by interleukin-6, a cytokine synthesized and released from activated monocytes.23 In patients with unstable angina, monocyte tissue factor expression and plasma CORONARY
fibrinogen correlate closely l4 ; both correlate directly with the degree of activation of the coagulation system and with fibrin formation.‘5.26 A kinetic model has been proposed that predicts a direct relation between plasma fibrinogen concentration and the quantity of fibrin generated in response to thrombin.” Considered collectively, these observations support the associations between C-reactive protein and the occurrence of clinical events in Liuzzo’s study of 3 1 patients6 and between fibrinogen and in-hospital outcome in our study. Whereas C-reactive protein is a nonspecific acute-phase reactant, fibrinogen is directly involved in the thrombotic process and is genetically regulated, 28making it a biologically attractive marker for clinical events. In the ECAT study, baseline measurements of C-reactive protein and fi-
ARTERY DISEASE,jPLASMA FIBRINOGEN AFTER INFARCTION
145
brinogen were correlated strongly (r=0.49; p
THE AMERICAN JOURNAL OF CARDIOLOGYa
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and clinical events because fibrinogen can be measured reliably in most experienced laboratories. Although we found that an elevated fibrinogen level at the time of hospital admission was associated with a poor clinical outcome among patients with unstable angina, we cannot comment on its prognostic superiority to other acute-phase proteins.6,22The complexity of unstable angina makes it unlikely that one biochemical marker can stand alone in predicting outcome among individual patients. Conclusions: An elevated fibrinogen concentration at the time of hospital admission is modestly associated with an increased incidence of coronary ischemit events among patients with unstable angina and myocardial ischemia at rest. Our results, considered along with emerging evidence of an inflammatory component in the evolution and clinical expression of coronary artery disease, strengthen the pathobiologic link between atherosclerosis, inflammation, thrombosis, and coronary events. Future work in the area of acute coronary syndromes should consider new avenues of investigation focusing on inflammatoly mediators and acute-phase proteins.
1. Munro JM. Cotran RS. The pathogen&s of atherosclerosis: atherogenesis and inflammation. Lob Inwsr 1988;58:249-261. 2. Stemme S, Helm J, Hansson GK. T lymphocytes in human atherosclerotic plaques are memory cells expressing CD45RO and the inegrin VLA-1. -Ir&erioscler Thmrnb 1992;12:206-211. 3. Van der Wal AC, Becker .4E, Van der Loos CM, Das PK. Site of intimal rupture or erosion of thrombosed coronary atherosclerotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology. Cimrlarion 199-l:89:36-44. 4. Hnnsson GK, Helm J, Jonasson L. Detection of activated T-lymphocytes in the human atherosclerotic plaque. An1 J Path01 1989;135:169- 175. 5. Bararh P. Fishbein MC, Cao J, Berenson J. Helfant RH, Forrester JS. Detection and localization of tumor necrosis factor in human atheroma. Am .I Cardiol 1990;65:297-302. 6. Liuzzo G. Biasucci LM, G&more R, Grillo RL, Rebuzzi AG, Pepys MB, Maseri .4. The prognostic value of C-reactive protein and serum amyloid A protein in severe unstable angina. N Engl .I Med 1994;331:417-424. 7. Fatah K, Hamsten A, Blomblck B, Blomblck M. Fibrin gel network characteristics and coronary heart disease: relations to plasma fibrinogen concentration. acnte phase protein. semm lipoproteins and coronary atherosclerosis. Thronzb Haemosr 1992;68:130-135. 8. The TIMI III B Investigators. Effects of tissue plasminogen activator and a comparison of early invasive and conservative strategies in unstable angina and non-Q wave myoczmlial infarction: results of the TIM1 III B Trial. Circulation 1994:59: 1515- 1556. 9. Clauss A. Gerinnungsphysioloische Schnellmethode zur bestimung des fibrinogens. Acfn Haernafol (Basel) 1957:17:237-246. 10. Geffken D, Keating F. Kennedy M, Cornell E, Bovill E, Tracy R. The measurement of fibrinogen in population-based research: studies on instmmentarion and methodology. A& Path01 Lab Med 1994; 118: 1106- 1109. 11. Stump DC, Top01 EJ, Chen AB, Hopkins A, Collen D. Monitoring of hemost&s parameters during coronm thrombolysis with recombinant tissue-type plasminogen activator. Thrornb Haemosi 1988;59:133- 137. 12. Carry M, Chorally V, Willerson JT, Weigec L. Ford-Hutchinson AW, Tagari P. Increased urinay leukotriene excretion in patients with cardiac ischemia: in viva evidence for 5.lipoxygenase activation. Circulnrior? 1992;85:230-236. 13. Berk BC. Weinrraub W, Alexander RW. Elevation of C-reactive protein in ‘-active“ coronay artery disease. Am .I Cardiol 1990;65:168-172. 14. Pepys MB. Balte ML. Acute phase proteins with special reference to Creactive protein and related proteins (pentaxins) and semm amyloid A protein. Adv Inzmurwl 1983;31:141-212. 15. Kushnrr I, Broder ML. Karp D. Control of the acute phase response: serum C-reactive protein kinetics after acute myocadial infarction. J Clin Invest 1978;61:235-242. 16. Wilhelmsen
L. Svardsudd K, Korsan-Bengtsen K, Larsson B, Welin L. Tibblin G. Fibrinogen as a risk factor for stroke and myocadial infarction. N El@ JMe!d 1984;311:501-505. 17. Kennel WB, Wolf PA, Castelli WP, D’Agostino RB. Fibrinogen and risk of cardiovascular disease: the Framingham Study. MMA 1987;258: 1183- 1186.
JULY i 5, 1990
18. Thompson SG, Kienast J. Pyke SDM, et al. Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. N Engl J Med 1995;332:635-641. 19. Meade TW, Vickers MV, Thompson SG. Seghatchian MJ. The effects of physiological levels of fibrinogen on platelet aggregation. Thromb Res 1985:38:527-534. 20. Lowe GDO, Forbes CD. Blood rheology and thrombosis. Clin Lab Haematd 1981;10:343-367. 21. Reganon E, Vila V, Aznar J, Lacueva V. Martinez V, Ruano M. Studies on the functionality of newly synthesized fibrinogen after treatment of acute myocardial infarction with streptokinase, increase in the rate of fibrinopeptide release. Thmmb Haemost 1993:70:97X-983. 22. Retzinger GS. Adsorption and coagulability of fibrinogen on atheromatous lipid surfaces. A~teriorcler Tbmmb Vast Bio/ 1995;15:786-792. 23. Le J, Vilcek J. Interleukin-6: a multifunctional cytokine regulating immune reactions and the acute phase protein response. Lab Zmest 1989:61:588-602. 24. Jude B, Agraou B, McFadden EP, Susen S, Baiters C, Lepellyey P, Vanhaesbroucke C. Devos P, Cosson A, Asseman P. Evidence for time-dependent activation of monocytes in the systemic circulation in unstable angina but not in acute myocardial infarction or in stable angina. Circulation 1994;90:16621668.
CORONARY
25. Nerd Semeri GG. Abbate R, Gori AM, Attanasio M, Martini F. Giusti B, Dabizzi P, Poggesi L, Modesti PA. Trotta F, Rostagno C, Boddi M, Gensini GF. Transient intermittent lymphocy@. acrivation is responsible for the instability of angina. Circulation 1993;88:790-797. 26. Ceriello A, Pi&i M, Giacomello R, Stel G, Fall&i E, Motz E, Lizzie S, Gonano F, Bartoli E. Fibrinogen plasma levels as a marker of thrombin activation: new insights on the role of fibrinogen as a cardiovascular risk factor. Thr-omb Haenzorr 1994:71:593-595. 27. Naski MC, Shafer JA. A kinetic model for the a-tbrombin-catalyzed conversion of plasma levels of fibrinogen to fibrin in the presence of antithrombin III. J Biol Chem 1992;11:1267-1274. 28. Bara L, Nicaud V, Tiret L, Cambien F, Samama MM, on behalf of the EARS group. Expression of a paternal history of premature myocardial infarction on fibrinogen, factor VIIC and PAI- in European offspring: the EARS Study. Thrornb Haemost 1994;71:434-430. 29. Made TW, Mellows S, Brozovic M, et al. Haemostatic function and ischaemic heart disease: principal results of the Northwick Park Heart Stud)<. Laker 1986;2:533-537. 30. Rosenson RS, Tangney CC, Hafner JM. Intraindividual variability of fibrinogen levels and cardiovascular risk profile. Arteriosckr Thrornb 1994;14:1928-1932.
ARTERY DISEASE/PLASMA FIBRINOGEN AFTER INFARCTION
147
taneous ischemia (p=O.O03) had higher fibrinogen concentrations than those without these events. This association was confined to patients with unstable angina. A baseline fibrinogen concentration 2300 mg/dl was associated with a modest trend toward an increased risk of death, myocardial infarction, or spontaneous ischemia (odds ratio 1.6 1,95% confidence interval 1.02 to 2.52; p=O.O4). Elevation of fibrinogen, a readily measurable acute-phase protein, at the time of hospital admission is associated with coronary ischemic events and a poor clinical outcome in patients with unstable angina. (Am J Cardiol 1996;78: 142- 147)
istologic studies have shown that atheroscleH rotic plaques contain foci of macrophages, monocytes, and activated lymphocytes.‘-’ The cy-
bolysis in Myocardial Infarction (TIM1 IIIB j trial, we conducted a prospective study to examine the association between fibrinogen concentrations and clinical events.
tokine secretory capacity of monocytes expressing tumor necrosis factor, interferon-y, interleukin-1, interleukin-6, and intracellular adhesion molecules is also increased.4%5Markers of biologic inflammation could conceivably facilitate the premorbid diagnosis of atherosclerosis, predict clinical events, and potentiate the development of new therapies. In a recent study,6 the acute-phase reactants Creactive protein and amyloid A protein were elevated in most patients with unstable angina. The patients with elevated levels of these proteins had a less favorable clinical course than did those with normal levels. Fibrinogen, another acute-phase protein, has been identified in several large-scale epidemiologic studies as an independent predictor of thrombotic cardiovascular events, and, because it is a pivotal component of the coagulation cascade, it may be more directly involved in the clinical expression of atherosclerotic coronary artery disease than are nonspecific markers of inflammation.7 Because fibrinogen was measured at serial time points in the ThromFrom the Cardiovascular Thrombosis Research Center, Uni,\iersity of Massachusetts Medical School, Worcester, Massachusetts; the LabUniveroratoy for Biochemistry Research, De artment of Pathology, sibi of Vermont Medical School, Coic L ester, Vermont; the Maryland Medical Research Institute, Baltimore, Mar$and; and the Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts. Manuscript recei\/ed August 10, 1995; revised manuscript received and acceptedJanuary 25, 1996. Address for reprints: Richard C. Becker, MD, Department of Medicine, University of Massachusetts Medical Center, 5.5 Loke Avenue North, Worcester, Massachusetts.
142
0 1996 by Excerpta Medico, All rights reserved.
Inc.
METHODS
The TIM1 III trial design has been reported previously.’ In brief, to be eligible for study participation, a patient was required to have experienced chest pain at rest presumed to be ischemic in origin, lasting 2.5 minutes but not >6 hours. Symptoms must have occurred within 24 hours of enrollment, accompanied by objective evidence of ischemic heart disease. The latter was defined as ( 1) new or presumably new electrocardiographic evidence of ischemia in at least 2 contiguous leads ( z-O.1 mV ST-segment elevation lasting <30 minutes, or transient/persistent ST-segment depression or T-wave inversion during an episode of rest pain within the prior 7 days ) , or (2 ) documented coronary artery disease (a history of previous myocardial infarction [MI], ~70% luminal diameter stenosis on a prior coronary angiogram, or an abnormal exercise thallium scan). Patients were excluded if they had a treatable cause of unstable angina, had experienced MI within the preceding 21 days, had undergone coronary angioplasty within 6 months, or had coronary bypass grafting at any time. Initial management: All patients received a full complement of anti-ischemic medication, including a ,8 blocker, calcium channel antagonist, and a nitrate preparation. Patients received intravenous heparin in sufficient quantity to maintain the activated partial thromboplastin time at 1.5 to 2.0 times laboratory control values. Aspirin, 325 mglday, was begun on 0002.9 149/96/s 15 .OO PII 50002.9149(96)00247-O
the second hospital day and continued for at least 1 year. Treatment/strategy: Patients were assigned randomly, using a 2 x 2 factorial design, to treatment with tissue plasminogen activator (tPA; Activase@ Genentech, South San Francisco, California) or placebo. The total dose of tPA was 0.8 mg/kg (maximal dose 80 mg) given intravenously over 90 minutes (one third of the total dose was given as a bolus, not to exceed 20 mg) . Patients were also assigned to either an early invasive or an early conservative strategy. Definitions: Spontaneous ischemia was defined as recurrent chest discomfort at rest, accompanied by ST-segment or T-wave changes on a 12-lead electrocardiogram. Blood was sampled for creatine kinase (CK) and CK-MB at 0, 4, 12, 24, 48, and 72 hours after randomization, and every 8 hours for a total of 24 hours when pain recurred. A CK-MB above the normal range or a total CK twice normal on the baseline, 4-hour, or 12-hour sample was considered evidence of infarction. Reinfarction was defined as CK or CK-MB elevation greater than the upper limit of normal. All end points were confirmed by a separate mortality and morbidity classification committee. Measurements: Blood was drawn into specially prepared collection tubes containing a final concentration of 4.5 mmol/L ethylenediaminetetraacetic acid, 50 pmol/L D-Phe-Pro-Arg chloromethyl ketone (PPACK), and 150 KIU/ml aprotinin. Fibrinogen levels were determined using the method of Clauss’ as modified for a semiautomated fibrometer (BBL, Hunt Valley, Maryland). Studies in our core laboratory indicated that a 45minute preincubation of the test plasma at 37°C was required to remove the antithrombin effect of active PPACK, lo thus allowing accurate estimation of the fibrinogen levels from the clotting rate. Heparin at plasma concentrations of up to 10 U/ml has no effect on this assay.” Statistical analysis: The mean, SD, and median of fibrinogen values were calculated for the 6 time points representing the protocol times for blood collection. Comparison of the pretreatment fibrinogen levels with post-treatment levels was accomplished using paired t tests. Comparison of fibrinogen levels for patients with and without clinical events was performed using Wilcoxon rank sums. When comparing fibrinogen levels collected after study entry (e.g., at 96 hours), patients with clinical events before the collection time were excluded from the comparison. Because of the large number of statistical hypotheses tested in TIM1 IIIB, p values
TABLE I Plasma Fibrinogen Sompling
I
Values at Six Predetermined Times (TIMI IllB (n = 1,473)
Time
12h 24 h 48 h 96 h
1.304
11264 1,104 versus baseline;
TIMI = Thrombolysis
’ p = 0.04
in Myocardiol
(mg/dl) I
1,339 1,329 1,314
Pretreatment 50 min
* p ~0.001
Fibrinogen
Number of Patients
Mean
SD
293 269* 265* 283’ 320* 372*
a2 74 a3 86 97 113
258 276 307 360
versus baseline.
Infarction
trial.
24 hours. This decrease was particularly evident in patients who received tPA. Beyond 24 hours, fibrinogen levels increased, surpassing pretreatment values in all groups. The greatest increase was observed in patients with non-Q-wave MI (Figure 1). The association between baseline fibrinogen concentration and in-hospital ( I 10 days) clinical events is outlined in Table II. No association was found for MI (p=O.70), death (p=O.64), or the combined outcome of death or MI (p=O.56); however, patients with spontaneous ischemia (p=O.O04) and the combined unsatisfactory outcome of death, MI, or spontaneous ischemia (p=O.O03) had higher baseline fibrinogen values than those without these events. The association between baseline fibrinogen level and inhospital ischemic events was confined to patients with a diagnosis of unstable angina (Table III). By logistic regression analysis, a baseline fibrinogen level >300 mg/dl was associated with a trend toward an increased risk of death, MI, or spontaneous ischemia (odds ratio 1.61, 95% confidence interval 1.02 to 2.52; p=O.O4). When adjusted for other covariables, including age, sex, prior infarction, tPA treatment, strategy, ST-segment deviation, and CK elevation, the association between baseline fibrinogen and clinical outcome was less striking (odds ratio 1.50, 95% confidence interval 0.95 to 2.38; p=O.O8). The association between baseline and 96-hour fibrinogen levels and clinical events at 42 days is shown in Table IV. A trend toward increased fibrinogen levels at baseline and spontaneous ischemia (p=O.O2) and the combined outcome of MI, death, or spontaneous ischemia (p=O.O2) was observed. There was no association between 96-hour (peak) fibrinogen and 42-day clinical events in any of the patient groups.
DISCUSSION
Previous studies have reported increased levels of acute-phase proteins in patients with coronary artery disease, l2 unstable angina,6’L3’14and MI,15 but most of these studies did not specifically investigate their prognostic importance. The results of our study, the RESULTS Plasma fibrinogen concentrations for the 6 sam- largest to date of patients with myocardial ischemia pling points are listed in Table I. There was an initial at rest, confirm that an elevated baseline fibrinogen decrease in fibrinogen levels at 50 minutes that per- level portends an increased risk of in-hospital corosisted, although to a lesser degree, for the first 12 to nary ischernic events. CORONARY
ARTERY DISEASE/PLASMA
FIBRINOGEN AFTER INFARCTION
143
OIPA I Placebo ohservativeStrategy slnvasive Strategy i
600-
500.
Fibrinogen (mgldl)
Fibrinogen (mgldl)
Baseline 50th. 12Hr. 24Hr. 48Hr. 96Hr.
Baseline 50Mm. 12Hr. 24Hr. 48Hr. 96Hr.
Unstable Angina
Non-Q Wave MI
FIGURE 1. Mean fibrinogen values at the 6 sampling times according to treatment (tissue plasminogen activator WA1 vs placebo), strategy (invasive vs conservative), and diagnosis (unstable angina vs non-Q-wave myocardial infarction [MI]).A decrease was observed within 50 minutes of enrollment that was most pronounced in patients given tPA. Levels increased after 24 hours and exceeded baseline values by 96 hours in all patient groups.
TABLE II Baseline
Plasma
Fibrinogen
Values
According
to the
Occurrence
of Clinical Pretreatment
End
Point
Myocardial
n
N infarction
End
Points
at
Fibrinogen
10
Days
(TIMI
IIIB)
(N
=
1,473)
(mg/dl)
Mean
SD
Median
p Value*
301
293
97 82
290 282
0.70
0.64
(MI)
73
YES No
63
1,400
1,263
Death 1,452
1,316
297 293
52 83
299 282
86 1.387
68 1,258
301
94 82
291
293
281
0.56
305 290
82 82
296 280
0.004
305 290
81
82
296 280
0.003
21
Yes No Death
or MI
Yes No Spontaneous
ischemia 310
Yes
281
1,163
No Ml,
10
death,
or spontaneous
1,045
ischemia
322
Yes
286
1,151
No * Wilcoxon Abbreviation
[rank
1,040
sums).
OS in Table
I
A number of prospective epidemiologic studies have shown a strong association between elevated plasma fibrinogen levels and the risk of ischemic heart disease and stroke.‘6*17In the European Concerted Action on Thrombosis and Disabilities (ECAT) Angina Pectoris Study, l8 fibrinogen level was an independent predictor of subsequent MI and 144
THE
AMERICAN
JOURNAL
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CARDIOLOGY@
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78
sudden death. Patients with and without events had fibrinogen values of 328 -t 0.74 and 300 f: 0.71 mg/ dl, respectively. Our findings were similar, and suggest that a fibrinogen concentration >300 mg/dl in the setting of either accelerated angina or angina at rest is associated with an increased risk of coronary events. Because fibrinogen is an essential component JULY
15,
1996
TABLE III Baseline
Plasma
Fibrinogen
Values
According
to the Occurrence
of Clinical
Pretreatment Patients With End Point Myocardial infarction (MI) Yes No Death Yes No Death or MI Yf?S No Spontaneous ischemia Yes No MI, death, or spontaneous ischemia Yes No + Wilcoxon Abbreviation
(rank
Angina
Values According on Day 4 (n = 1,463)
Myocardial infarction (MI) Yes No Death Yes No Death or MI Yes No Spontaneous ischemia Yes NO Ml, death, or spontaneous ix :hemia Yes No (rank
Non-Q-Wave
MI (N = 477)
N
n
Mean
SD
Median
p Value*
N
n
Mean
SD
Median
53 940
46 855
309 295
107 84
281 286
0.61
20 A57
17 405
279 290
61 76
296 276
0.89
8 985
4 897
292 295
68 86
284 286
13 464
6
0.99
Al6
300 289
A6 76
299 277
0.49
57 936
A8 853
307 295
105 84
281 286
0.65
29 448
20 402
286 289
59 76
296 276
0.71
210 783
193 708
311 291
85 85
302 280
0.001
99 378
87 335
290 289
73 76
288 274
0.70
215 778
196 705
311 291
85 85
302 280
0.001
106 371
88 333
291 289
73 76
289 274
0.61
to the Occurrence
Patients With End Point
Wilcoxon
Patients With
(N = 993)
of Clinical
pValue*
End Points at 42 Days (TIMI IIIB): Pretreatment
l
(mg/dl)
I.
TABLE IV Fibrinogen
Abbreviation
Fibrinogen
sums).
OS in Table
All Patients Alive
Unstable
End Points at 10 Days (TIMI IIIB)
Unstable
Angina
(N = 1,473)
Fibrinogen
(mg/dl)
Patients With
Non-Q-Wave
N
n
Mean
SD
Median
pValue
0.88
87 1,376
64 1,037
377 373
121 113
384 358
o.i2*
301 281
16
0.30*
1,441
434 372
178 112
380 360
0.25*
90 82
282 282
100
72
0.95*
1,363
1,029
382 373
122 113
382 358
O.d8*
302 291
81 83
290 280
0.02*
333 1,130
252 849
381 371
112 114
381 356
0.11’
302 291
80 83
290 280
0.02*
341 1,122
259 842
381 371
112 114
378 356
0.1
N
n
Mean
SD
Median
90 1,383
79 1,247
297 293
94 82
276 282
32 1,441
18 1,308
306 293
58 83
110 1,363
89 1,237
297 293
337 1,136
306 1,020
351 1,122
313 1,013
p Value
22
1,085
Ml (N = 477)
1
sums).
as in Table
I
in normal hemostasis, it is not unexpected that perturbations in this system could be linked to pathologic thrombosis.‘9-20 New fibrinogen is highly thrombogenic, and the thrombi formed typically have a tight, rigid, and space-filling fibrin network.*’ Furthermore, hydrophobic, atheromatous lipid surfaces, particularly those rich in cholesterol esters, are predisposed to thrombosis by virtue of their inherent capacity to bind functional fibrinogen.22 The hepatic synthesis of fibrinogen, as well as of other acute-phase proteins including C-reactive protein, amyloid A protein, haptoglobin, ceruloplasmin, and cu,-antitrypsin, is regulated primarily by interleukin-6, a cytokine synthesized and released from activated monocytes.23 In patients with unstable angina, monocyte tissue factor expression and plasma CORONARY
fibrinogen correlate closely l4 ; both correlate directly with the degree of activation of the coagulation system and with fibrin formation.‘5.26 A kinetic model has been proposed that predicts a direct relation between plasma fibrinogen concentration and the quantity of fibrin generated in response to thrombin.” Considered collectively, these observations support the associations between C-reactive protein and the occurrence of clinical events in Liuzzo’s study of 3 1 patients6 and between fibrinogen and in-hospital outcome in our study. Whereas C-reactive protein is a nonspecific acute-phase reactant, fibrinogen is directly involved in the thrombotic process and is genetically regulated, 28making it a biologically attractive marker for clinical events. In the ECAT study, baseline measurements of C-reactive protein and fi-
ARTERY DISEASE,jPLASMA FIBRINOGEN AFTER INFARCTION
145
brinogen were correlated strongly (r=0.49; p
THE AMERICAN JOURNAL OF CARDIOLOGYa
VOL. 78
and clinical events because fibrinogen can be measured reliably in most experienced laboratories. Although we found that an elevated fibrinogen level at the time of hospital admission was associated with a poor clinical outcome among patients with unstable angina, we cannot comment on its prognostic superiority to other acute-phase proteins.6,22The complexity of unstable angina makes it unlikely that one biochemical marker can stand alone in predicting outcome among individual patients. Conclusions: An elevated fibrinogen concentration at the time of hospital admission is modestly associated with an increased incidence of coronary ischemit events among patients with unstable angina and myocardial ischemia at rest. Our results, considered along with emerging evidence of an inflammatory component in the evolution and clinical expression of coronary artery disease, strengthen the pathobiologic link between atherosclerosis, inflammation, thrombosis, and coronary events. Future work in the area of acute coronary syndromes should consider new avenues of investigation focusing on inflammatoly mediators and acute-phase proteins.
1. Munro JM. Cotran RS. The pathogen&s of atherosclerosis: atherogenesis and inflammation. Lob Inwsr 1988;58:249-261. 2. Stemme S, Helm J, Hansson GK. T lymphocytes in human atherosclerotic plaques are memory cells expressing CD45RO and the inegrin VLA-1. -Ir&erioscler Thmrnb 1992;12:206-211. 3. Van der Wal AC, Becker .4E, Van der Loos CM, Das PK. Site of intimal rupture or erosion of thrombosed coronary atherosclerotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology. Cimrlarion 199-l:89:36-44. 4. Hnnsson GK, Helm J, Jonasson L. Detection of activated T-lymphocytes in the human atherosclerotic plaque. An1 J Path01 1989;135:169- 175. 5. Bararh P. Fishbein MC, Cao J, Berenson J. Helfant RH, Forrester JS. Detection and localization of tumor necrosis factor in human atheroma. Am .I Cardiol 1990;65:297-302. 6. Liuzzo G. Biasucci LM, G&more R, Grillo RL, Rebuzzi AG, Pepys MB, Maseri .4. The prognostic value of C-reactive protein and serum amyloid A protein in severe unstable angina. N Engl .I Med 1994;331:417-424. 7. Fatah K, Hamsten A, Blomblck B, Blomblck M. Fibrin gel network characteristics and coronary heart disease: relations to plasma fibrinogen concentration. acnte phase protein. semm lipoproteins and coronary atherosclerosis. Thronzb Haemosr 1992;68:130-135. 8. The TIMI III B Investigators. Effects of tissue plasminogen activator and a comparison of early invasive and conservative strategies in unstable angina and non-Q wave myoczmlial infarction: results of the TIM1 III B Trial. Circulation 1994:59: 1515- 1556. 9. Clauss A. Gerinnungsphysioloische Schnellmethode zur bestimung des fibrinogens. Acfn Haernafol (Basel) 1957:17:237-246. 10. Geffken D, Keating F. Kennedy M, Cornell E, Bovill E, Tracy R. The measurement of fibrinogen in population-based research: studies on instmmentarion and methodology. A& Path01 Lab Med 1994; 118: 1106- 1109. 11. Stump DC, Top01 EJ, Chen AB, Hopkins A, Collen D. Monitoring of hemost&s parameters during coronm thrombolysis with recombinant tissue-type plasminogen activator. Thrornb Haemosi 1988;59:133- 137. 12. Carry M, Chorally V, Willerson JT, Weigec L. Ford-Hutchinson AW, Tagari P. Increased urinay leukotriene excretion in patients with cardiac ischemia: in viva evidence for 5.lipoxygenase activation. Circulnrior? 1992;85:230-236. 13. Berk BC. Weinrraub W, Alexander RW. Elevation of C-reactive protein in ‘-active“ coronay artery disease. Am .I Cardiol 1990;65:168-172. 14. Pepys MB. Balte ML. Acute phase proteins with special reference to Creactive protein and related proteins (pentaxins) and semm amyloid A protein. Adv Inzmurwl 1983;31:141-212. 15. Kushnrr I, Broder ML. Karp D. Control of the acute phase response: serum C-reactive protein kinetics after acute myocadial infarction. J Clin Invest 1978;61:235-242. 16. Wilhelmsen
L. Svardsudd K, Korsan-Bengtsen K, Larsson B, Welin L. Tibblin G. Fibrinogen as a risk factor for stroke and myocadial infarction. N El@ JMe!d 1984;311:501-505. 17. Kennel WB, Wolf PA, Castelli WP, D’Agostino RB. Fibrinogen and risk of cardiovascular disease: the Framingham Study. MMA 1987;258: 1183- 1186.
JULY i 5, 1990
18. Thompson SG, Kienast J. Pyke SDM, et al. Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. N Engl J Med 1995;332:635-641. 19. Meade TW, Vickers MV, Thompson SG. Seghatchian MJ. The effects of physiological levels of fibrinogen on platelet aggregation. Thromb Res 1985:38:527-534. 20. Lowe GDO, Forbes CD. Blood rheology and thrombosis. Clin Lab Haematd 1981;10:343-367. 21. Reganon E, Vila V, Aznar J, Lacueva V. Martinez V, Ruano M. Studies on the functionality of newly synthesized fibrinogen after treatment of acute myocardial infarction with streptokinase, increase in the rate of fibrinopeptide release. Thmmb Haemost 1993:70:97X-983. 22. Retzinger GS. Adsorption and coagulability of fibrinogen on atheromatous lipid surfaces. A~teriorcler Tbmmb Vast Bio/ 1995;15:786-792. 23. Le J, Vilcek J. Interleukin-6: a multifunctional cytokine regulating immune reactions and the acute phase protein response. Lab Zmest 1989:61:588-602. 24. Jude B, Agraou B, McFadden EP, Susen S, Baiters C, Lepellyey P, Vanhaesbroucke C. Devos P, Cosson A, Asseman P. Evidence for time-dependent activation of monocytes in the systemic circulation in unstable angina but not in acute myocardial infarction or in stable angina. Circulation 1994;90:16621668.
CORONARY
25. Nerd Semeri GG. Abbate R, Gori AM, Attanasio M, Martini F. Giusti B, Dabizzi P, Poggesi L, Modesti PA. Trotta F, Rostagno C, Boddi M, Gensini GF. Transient intermittent lymphocy@. acrivation is responsible for the instability of angina. Circulation 1993;88:790-797. 26. Ceriello A, Pi&i M, Giacomello R, Stel G, Fall&i E, Motz E, Lizzie S, Gonano F, Bartoli E. Fibrinogen plasma levels as a marker of thrombin activation: new insights on the role of fibrinogen as a cardiovascular risk factor. Thr-omb Haenzorr 1994:71:593-595. 27. Naski MC, Shafer JA. A kinetic model for the a-tbrombin-catalyzed conversion of plasma levels of fibrinogen to fibrin in the presence of antithrombin III. J Biol Chem 1992;11:1267-1274. 28. Bara L, Nicaud V, Tiret L, Cambien F, Samama MM, on behalf of the EARS group. Expression of a paternal history of premature myocardial infarction on fibrinogen, factor VIIC and PAI- in European offspring: the EARS Study. Thrornb Haemost 1994;71:434-430. 29. Made TW, Mellows S, Brozovic M, et al. Haemostatic function and ischaemic heart disease: principal results of the Northwick Park Heart Stud)<. Laker 1986;2:533-537. 30. Rosenson RS, Tangney CC, Hafner JM. Intraindividual variability of fibrinogen levels and cardiovascular risk profile. Arteriosckr Thrornb 1994;14:1928-1932.
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