THROMBOSIS RESEARCH 58; 653-656,199O 0049-3848/90 $3.00 + .OOPrinted in the USA. Copyright (c) 1990 Pergamon Press pk. All rights reserved.
BRIEF
WARFARIN
COMMUNICATION
HAS
NO NEGATIVE
IMPACT
ON FIBRINOLYSIS
Pal Smith, Harald Arnesen, Trine Opstad and Peter Kierulf' Department of Medicine, Red Cross,Clinic and Central Laboratory, Ulleval Hospital , Oslo, Norway
(Received 12.3.1990; accepted in original form 23.3.1990 by Editor U. Abildgaard)
INTRODUCTION
The risk of metabolic side effects induced by drugs has been highlighted by a number of commentaries (1). Moreover, a previous study suggested that warfarin might bring about an increase in triglycerides and a consequent decline in fibrinolytic capacity. The results were not conclusive, as the number of patients was small and the level of triglycerides at entry was not known (2). In the present prospective study we have compared the impact of long-term treatment with warfarin with that of placebo on blood lipids and fibrinlytic variables in patients with coronary artery disease. METHODS
Sixty-five consecutive patients from the Warfarin Re-Infarction Study were asked to participate in this additional investigation. Briefly, this placebocontrolled study assessed the effect of long-term treatment with warfarin on mortality and reinfarction after acute myocardial infarction (3). For the purpose of the present study, patients were examined and blood samples collected prior to start of treatment and then after 12 months. All tests were performed in the fasting condition between 8 and 10 a.m. Before stasis, blood was collected for determination of plasminogen activator inhibitor (PAI-l), lipids and baseline t-PA. Venous stasis was applied to the upper arm for 20 minutes ------_------a-_-w-w----------
Key words: Warfarin,
fibrinolytic
capacity,
653
lipids
WARFARIN AND FIBRINOLYSIS
654
Vol.58, No.6
(4). Blood for determination of fibrinolytic capacity by the ECLT and t-PA measurements were collected from an antecubital vein of the occluded arm just prior to release of the stasis. Blood for t-PA measurements was acidified (5) and snap-frozen in liquid nitrogen immediately after centrifugation. Fibrinolytic activity was determined as euglobulin clot lysis time (ECLT) (6), expressed in minutes. An ECLT 1 60 minutes was taken as pathological (7). Blood lipids were determined enzymatically by conventional methods (Boehringer Mannheim GmbH, FRG). PAIwas measured according to Chmielewska (8) using a commercial kit (ImulyseR, Biopool, Sweden), whereas t-PA activity was assessed as described by Wiman (5). Comparisons were made according to treatment allocation before start of treatment and after 12 months. Continuous variables were tested with the Wilcoxon rank sum test, and categorical data were tested with the Chi-square test. An LY less than 0.05 was taken as significant. RESULTS The two groups were not completely balanced regarding clinicopathological variables at baseline as assignment to warfarin and placebo respectively was blinded (Table 1). Comparatively
TABLE I
Comparison of the two treatment groups at baseline
Age Body Mass Index Days from AM1 to randomization
Warfarin N=35 62.2 (6.8) 25.1 (2.8)
Placebo N=30 61.4 (9.3) NS 25.1 (3.4) NS
27.0 (33)
30.0 (15)
N
Male Smokers Betablockers Diuretics
32 11 14 6
(91) (31) (40) (17)
NS
t%)
26 16 18 5
(87) (53) (60) (16)
NS NS NS NS
fewer used betablockers among the placebo group than in the beta-blockers warfarin group. The proportion of non-selective were equally distributed among the groups. The median prothrombin time level in the anticoagulated group for the follow-up period was 3.3 in terms of International Normalized Ratio (INR) (8).
Vol. 58, No. 6
WARFARIN AND FIBRINOLYSIS
Before start of therapy 14 subjects in the warfarin group had an ECLT less than 60 minutes compared with 17 patients assigned to placebo. After 12 months, 23 subjects in the warfarin group exhibited an ECLT less than 60 minutes, versus 15 in the placebo group (X*=1.6, not significant). Accordingly, none of the recorded fibrinolytic variables showed any important changes. The lipids also remained stable (Table 2).
TABLE II Examined parameters before and 12 months after start of treatment. VO denotes venous occlusion. Geometric means and (SD). Lipids and glucose in mmol/L, PAI- and t-PA in units/ml and fibrinogen in g/L.
Variable
Before 12 months Warfarin Placebo Warfarin Placebo Cholesterol 6.2 (1.0) 6.4 (0.9) 6.3 (1.9) 6.2 (1.7) HDL 1.0 (0.3) 1.1 (0.3) 1.0 (0.3) 1.0 (0.3) TG 1.6 (2.4) 1.7 (1.6) 1.6 (1.9) 1.3 (1.0) Glucose 5.5 (1.7) 5.5 (1.4) 5.2 (2.6) 5.0 (1.7) tPA (basal) 1.5 (3.6) 1.3 (3.6) 0.9 (3.2) 0.8 (2.3) tPA (VO) 9.9 (16) 13.7 (12) 9.9 (12) 9.0 (9) PA1 1 16.5 (17) 14.2 (12) 15.5 (18) 13.0 (18) Fibrinogen 2.4 (1.5) 2.3 (1.3) 2.6 (0.8) 2.4 (0.6)
DISCUSSION Our previous study suggested an association of warfarin treatment with hypertriglyceridemia (2). A major concern was that hypertriglyceridemia is related to decreased fibrinolytic activity (10) I which might interfere with the purpose of anticoagulant therapy. As the previous study was small and had no data on lipoproteins at entry, we pointed out the need for a confirmative study (2). No important change in the triglyceride level was observed during our study, nor was there any shift among the other lipids the trend towards (Table II). Despite appearing impressive, nomalization of the ECLT in the warfarin group did not reach the level of statistical significance. Moreover, none of the single factors of the fibrinolytic system that were recorded indicates a shift towards improvement. Thus, the present study does not support the idea that warfarin has any negative impact on blood lipids, nor any untoward effect on the fibrinolytic activity.
WARFARIN AND FIBRINOLYSIS
Vol. 58, No. 6
REFERENCES 1. WALLACE RB, HUNNUNGHAKE DB, REILAND S, BARRET-CONNOR E, MACKENTHUN A, HOOVER J, WAHL P. Alterations of plasma high-density lipoprotein cholesterol levels associated with consumption of selected medications. The Lipid Research Clinics Program Prevalence Study. Circulation 62 ~sunnl. IV), 77-82, 1980. 2. ARNESEN H, SMITH P, ASPELUND EB. Changes in fibrinolytic capacity and lipoprotein pattern during long-term treatment with warfarin. Thrombos Res 44, 229-33,1986. 3. SMITH P, ARNESEN H, HOLME I. The effect of warfarin on mortality and reinfarction after myocardial infarction. N Enul J Med (Submitted). 4. ROBERTSON BR, PANDOLFI M, NILSSON IM. Fibrinolytic capacity in healthy volunteers as estimated from effect of venous occlusion of arms. Acta Chir. Stand. 138, 429-36,1972. 5. WIMAN B, MELLBRING G, RANBY M. Plasminogen activator release during venous stasis and exercise as determined by a new specific assay. Clin. Chim. Acta 127,279-88,1983. 6. NORDBY E, ARNESEN H, ANDERSEN P and GODAL HC. The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis. Stand J Haematol 25, 407-411, 1980. 7. ANDERSEN P, SMITH P, SELJEFLOT I, BRATAKER S, ARNESEN H. Effects of gemfibrozil on lipids and haemostasis after myocardial infarction. Thrombos Haemostas (In press). 8. CHMIELEWSKA J, RANBY M, WIMAN B. Evidence for a rapid inhibitor to tissue plasminogen activator in plasma. Thrombosis Res 31,427-36,1983. 9. LOELIGER EA, POLLER L, SAMAMA M, THOMSON JM, VAN DEN BESSELAR A, VERMYLEN J, VERSTRAETE M. Questions and answers on prothrombin time standardisation in oral anticoagulant control. Thrombos Haemostas 54, 515-17, 1985. 10. ANDERSEN P, ARNESEN H, HJERMANN I. Hyperlipoproteinemia and reduced fibrinolytic activity in healthy coronary highrisk men. Acta Med. Stand. 209, 199-202,1981.
BRIEF
WARFARIN
COMMUNICATION
HAS
NO NEGATIVE
IMPACT
ON FIBRINOLYSIS
Pal Smith, Harald Arnesen, Trine Opstad and Peter Kierulf' Department of Medicine, Red Cross,Clinic and Central Laboratory, Ulleval Hospital , Oslo, Norway
(Received 12.3.1990; accepted in original form 23.3.1990 by Editor U. Abildgaard)
INTRODUCTION
The risk of metabolic side effects induced by drugs has been highlighted by a number of commentaries (1). Moreover, a previous study suggested that warfarin might bring about an increase in triglycerides and a consequent decline in fibrinolytic capacity. The results were not conclusive, as the number of patients was small and the level of triglycerides at entry was not known (2). In the present prospective study we have compared the impact of long-term treatment with warfarin with that of placebo on blood lipids and fibrinlytic variables in patients with coronary artery disease. METHODS
Sixty-five consecutive patients from the Warfarin Re-Infarction Study were asked to participate in this additional investigation. Briefly, this placebocontrolled study assessed the effect of long-term treatment with warfarin on mortality and reinfarction after acute myocardial infarction (3). For the purpose of the present study, patients were examined and blood samples collected prior to start of treatment and then after 12 months. All tests were performed in the fasting condition between 8 and 10 a.m. Before stasis, blood was collected for determination of plasminogen activator inhibitor (PAI-l), lipids and baseline t-PA. Venous stasis was applied to the upper arm for 20 minutes ------_------a-_-w-w----------
Key words: Warfarin,
fibrinolytic
capacity,
653
lipids
WARFARIN AND FIBRINOLYSIS
654
Vol.58, No.6
(4). Blood for determination of fibrinolytic capacity by the ECLT and t-PA measurements were collected from an antecubital vein of the occluded arm just prior to release of the stasis. Blood for t-PA measurements was acidified (5) and snap-frozen in liquid nitrogen immediately after centrifugation. Fibrinolytic activity was determined as euglobulin clot lysis time (ECLT) (6), expressed in minutes. An ECLT 1 60 minutes was taken as pathological (7). Blood lipids were determined enzymatically by conventional methods (Boehringer Mannheim GmbH, FRG). PAIwas measured according to Chmielewska (8) using a commercial kit (ImulyseR, Biopool, Sweden), whereas t-PA activity was assessed as described by Wiman (5). Comparisons were made according to treatment allocation before start of treatment and after 12 months. Continuous variables were tested with the Wilcoxon rank sum test, and categorical data were tested with the Chi-square test. An LY less than 0.05 was taken as significant. RESULTS The two groups were not completely balanced regarding clinicopathological variables at baseline as assignment to warfarin and placebo respectively was blinded (Table 1). Comparatively
TABLE I
Comparison of the two treatment groups at baseline
Age Body Mass Index Days from AM1 to randomization
Warfarin N=35 62.2 (6.8) 25.1 (2.8)
Placebo N=30 61.4 (9.3) NS 25.1 (3.4) NS
27.0 (33)
30.0 (15)
N
Male Smokers Betablockers Diuretics
32 11 14 6
(91) (31) (40) (17)
NS
t%)
26 16 18 5
(87) (53) (60) (16)
NS NS NS NS
fewer used betablockers among the placebo group than in the beta-blockers warfarin group. The proportion of non-selective were equally distributed among the groups. The median prothrombin time level in the anticoagulated group for the follow-up period was 3.3 in terms of International Normalized Ratio (INR) (8).
Vol. 58, No. 6
WARFARIN AND FIBRINOLYSIS
Before start of therapy 14 subjects in the warfarin group had an ECLT less than 60 minutes compared with 17 patients assigned to placebo. After 12 months, 23 subjects in the warfarin group exhibited an ECLT less than 60 minutes, versus 15 in the placebo group (X*=1.6, not significant). Accordingly, none of the recorded fibrinolytic variables showed any important changes. The lipids also remained stable (Table 2).
TABLE II Examined parameters before and 12 months after start of treatment. VO denotes venous occlusion. Geometric means and (SD). Lipids and glucose in mmol/L, PAI- and t-PA in units/ml and fibrinogen in g/L.
Variable
Before 12 months Warfarin Placebo Warfarin Placebo Cholesterol 6.2 (1.0) 6.4 (0.9) 6.3 (1.9) 6.2 (1.7) HDL 1.0 (0.3) 1.1 (0.3) 1.0 (0.3) 1.0 (0.3) TG 1.6 (2.4) 1.7 (1.6) 1.6 (1.9) 1.3 (1.0) Glucose 5.5 (1.7) 5.5 (1.4) 5.2 (2.6) 5.0 (1.7) tPA (basal) 1.5 (3.6) 1.3 (3.6) 0.9 (3.2) 0.8 (2.3) tPA (VO) 9.9 (16) 13.7 (12) 9.9 (12) 9.0 (9) PA1 1 16.5 (17) 14.2 (12) 15.5 (18) 13.0 (18) Fibrinogen 2.4 (1.5) 2.3 (1.3) 2.6 (0.8) 2.4 (0.6)
DISCUSSION Our previous study suggested an association of warfarin treatment with hypertriglyceridemia (2). A major concern was that hypertriglyceridemia is related to decreased fibrinolytic activity (10) I which might interfere with the purpose of anticoagulant therapy. As the previous study was small and had no data on lipoproteins at entry, we pointed out the need for a confirmative study (2). No important change in the triglyceride level was observed during our study, nor was there any shift among the other lipids the trend towards (Table II). Despite appearing impressive, nomalization of the ECLT in the warfarin group did not reach the level of statistical significance. Moreover, none of the single factors of the fibrinolytic system that were recorded indicates a shift towards improvement. Thus, the present study does not support the idea that warfarin has any negative impact on blood lipids, nor any untoward effect on the fibrinolytic activity.
WARFARIN AND FIBRINOLYSIS
Vol. 58, No. 6
REFERENCES 1. WALLACE RB, HUNNUNGHAKE DB, REILAND S, BARRET-CONNOR E, MACKENTHUN A, HOOVER J, WAHL P. Alterations of plasma high-density lipoprotein cholesterol levels associated with consumption of selected medications. The Lipid Research Clinics Program Prevalence Study. Circulation 62 ~sunnl. IV), 77-82, 1980. 2. ARNESEN H, SMITH P, ASPELUND EB. Changes in fibrinolytic capacity and lipoprotein pattern during long-term treatment with warfarin. Thrombos Res 44, 229-33,1986. 3. SMITH P, ARNESEN H, HOLME I. The effect of warfarin on mortality and reinfarction after myocardial infarction. N Enul J Med (Submitted). 4. ROBERTSON BR, PANDOLFI M, NILSSON IM. Fibrinolytic capacity in healthy volunteers as estimated from effect of venous occlusion of arms. Acta Chir. Stand. 138, 429-36,1972. 5. WIMAN B, MELLBRING G, RANBY M. Plasminogen activator release during venous stasis and exercise as determined by a new specific assay. Clin. Chim. Acta 127,279-88,1983. 6. NORDBY E, ARNESEN H, ANDERSEN P and GODAL HC. The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis. Stand J Haematol 25, 407-411, 1980. 7. ANDERSEN P, SMITH P, SELJEFLOT I, BRATAKER S, ARNESEN H. Effects of gemfibrozil on lipids and haemostasis after myocardial infarction. Thrombos Haemostas (In press). 8. CHMIELEWSKA J, RANBY M, WIMAN B. Evidence for a rapid inhibitor to tissue plasminogen activator in plasma. Thrombosis Res 31,427-36,1983. 9. LOELIGER EA, POLLER L, SAMAMA M, THOMSON JM, VAN DEN BESSELAR A, VERMYLEN J, VERSTRAETE M. Questions and answers on prothrombin time standardisation in oral anticoagulant control. Thrombos Haemostas 54, 515-17, 1985. 10. ANDERSEN P, ARNESEN H, HJERMANN I. Hyperlipoproteinemia and reduced fibrinolytic activity in healthy coronary highrisk men. Acta Med. Stand. 209, 199-202,1981.
