Usefulness of residual plasma fibrinogen after intravenous streptokinase for predicting delay or failure of reperfusion in acute myocardial infarction

Effect of reteplase on hemostasis variables: analysis of fibrin specificity, relation to bleeding complications and coronary patency

The first aim of the present study was to characterize the systemic and fibrin-specific lytic effect of reteplase in the treatment of patients with acute myocardial infarction. The second aim was to investigate the relation of hemostasis variables to risk of bleeding complications and to coronary patency. The present study is a hemostatic substudy of the German Recombinant Activator Study. Forty two patients have been treated with 10 MU of reteplase (Group A) and 100 patients with 15 MU of reteplase (Group B), given as a single bolus. Blood samples for assessment of fibrinogen, plasminogen, alpha-2-antiplasmin, fibrinogen degradation products (FDP) and D-dimers were obtained before and at 2, 4, 8, and 24 h after thrombolytic therapy. The median fibrinogen concentration was decreased from 279 to 169 mg/dl in Group A and from 254 to 92 mg/dl in Group B four hours after administration of reteplase. The decrease in fibrinogen was significantly more pronounced in Group B (P=0.0004). The median plasminogen concentration was decreased to 53% in Group A and to 33% in Group B two hours after administration of reteplase (P=0.0001). Alpha-2-antiplasmin was reduced to 27% and 17,5%, respectively (P=0.0007). D-Dimer levels were increased to 5.2 microg/ml in Group A and 11,6 microg/ml in Group B (P=0.02) and FDP levels to 3.0 microg/ml in Group A and 12,6 microg/ml in Group B (P=0.04). Patients with bleeding complications revealed significant lower nadir levels of fibrinogen than patients without bleeding complications (54 mg/dl versus 125.5 mg/dl, P=0.02). There was no significant difference in any hemostatic parameter between patients with patent and nonpatent infarct related arteries.

CONCLUSIONS

Reteplase causes a moderate systemic lytic effect comparable with other relative fibrin specific thrombolytic agents. An increase in the dose from 10 to 15 MU is associated with a marked increase in both fibrin specific and systemic lytic effect. Patients with bleeding complications reveal significant lower nadir levels of fibrinogen than patients without bleeding complications. Determination of any hemostatic parameter seems to be no useful method to predict efficacy of thrombolysis in terms of coronary patency in the individual patient.

Systemic lytic state is not a predictor of coronary reperfusion in acute myocardial infarction

To investigate why approximately one third of patients thrombolysed with streptokinase fail to reperfuse, we assessed the lytic status, antistreptokinase antibody and non invasive parameters of reperfusion in 95 consecutive patients with acute myocardial infarction treated with streptokinase for the first time. The lytic status was assessed by Clauss fibrinogen assay and thrombin clotting time before and 2 h after streptokinase infusion. Antistreptokinase antibody was measured prior to the infusion. Reperfusion was assessed by measurement of the 24:96 h troponin-T ratio (a ratio > 1 indicating reperfusion) and ST segment resolution 2 h post streptokinase. Ninety-two (97%) patients achieved a systemic lytic state with a fibrinogen titre of less than 1.0 g/l and thrombin clotting time ratio of > 2.5. Despite this, 27% failed to reperfuse with a mean 24:96 h troponin-T of 0.9, SD 0.6 vs. 3.4 +/- 3.2 in the reperfused group, (P < 0.0001). 83% of the reperfused group but none of the non reperfused group had ST segment resolution. No difference was observed in the levels of fibrinogen and thrombin clotting time between the reperfused 0.25 +/- 0.3 g/l; 6.9 +/- 4, and the non reperfused group 0.4 +/- 0.6 g/l; 7.9 +/- 2.6. No difference was observed in the levels of antistreptokinase antibody between the reperfused (median = 168 U/ml and the non reperfused (median = 177 U/ml). Failure to reperfuse with Streptokinase is not due to failure to achieve a lytic state. Therefore increased or accelerated dosages of streptokinase are unlikely to increase the rate of reperfusion.

Streptokinase induced defibrination assessed by thrombin time: effects on residual coronary stenosis and left ventricular ejection fraction

OBJECTIVE

To evaluate laboratory markers of defibrination early after thrombolytic therapy and to determine their relation to residual stenosis and left ventricular ejection fraction measured angiographically before discharge from hospital.

DESIGN

Prospective analysis of defibrination after streptokinase measured by fibrinogen assay and thrombin time to provide a comparison of these coagulation variables for predicting angiographic responses to treatment in patients with acute myocardial infarction.

SETTING

The coronary care unit of a district general hospital.

PATIENTS

44 patients with acute myocardial infarction treated by streptokinase infusion, all of whom underwent paired blood sampling before and one hour after streptokinase and cardiac catheterisation at a median of six (interquartile range 3-9) days later.

MAIN OUTCOME MEASURES

Assay of thrombin time and plasma fibrinogen concentrations one hour after streptokinase infusion. Relations between these coagulation variables and residual stenosis in the infarct related coronary artery and left ventricular ejection fraction. Separate analyses are presented for all patients (n = 44) and those with patency of the infarct related artery (n = 35).

RESULTS

Streptokinase infusion produced profound defibrination in every patient as shown by changes in thrombin time and circulating fibrinogen. Thrombin time after streptokinase infusion correlated significantly with both residual stenosis (r = -0.43, p < 0.005) and left ventricular ejection fraction (r = 0.38, p < 0.02). The importance of these correlations was emphasised by the interquartile group comparison which showed that a thrombin time > or = 49 seconds predicted a residual stenosis of 74% and an ejection fraction of 65%, compared with 90% and 49% for a thrombin time < or = 31 seconds (p < 0.01). When the analysis was restricted to patients with patency of the infarct related artery, the correlation between thrombin time and residual stenosis remained significant and group comparisons continued to show that patients in the highest quartile range had more widely patent arteries and better preservation of ejection fraction. Analysis of the fibrinogen data, on the other hand, showed insignificant or only marginally significant correlations with these angiographic variables.

CONCLUSIONS

Early after streptokinase infusion for acute myocardial infarction, the level of defibrination measured by thrombin time has an important influence on residual coronary stenosis and left ventricular ejection fraction at discharge from hospital, values above 49 seconds being associated with the best angiographic result.

A systemic non-lytic state and local thrombolytic failure of anistreplase (anisoylated plasminogen streptokinase activator complex, APSAC) in acute myocardial infarction

The relation between coronary thrombolysis and coagulation variables after administration of anistreplase (anisoylated plasminogen streptokinase activator complex, APSAC) was studied in patients with an acute myocardial infarction. Fifty eight consecutive patients with acute myocardial infarction were given 30 U of anistreplase intravenously within 4 hours of the onset of symptoms. A fall in the plasma concentration fibrinogen to less than 1.0 g/l 90 minutes after administration of anistreplase was considered to reflect a systemic lytic state. Coronary angiography was performed 48 hours after thrombolytic treatment. The overall patency rate was 74% (43/58). Patency rates were significantly different in patients with a systemic lytic (83% (43/52)) and a systemic non-lytic state (0% (0/6)). The absence of a systemic lytic state after anistreplase administration seemed to be highly predictive of the failure of coronary thrombolysis. Coagulation studies showed evidence of inhibition of anistreplase induced fibrinolytic activity which may explain the failure of thrombolytic treatment in patients with evidence of a systemic non-lytic state.

Acute anterior myocardial infarction: streptokinase prevents ventricular thrombosis independently of its effect on infarct size

Left ventricular thrombosis (LVT) is a frequent complication after acute anterior myocardial infarction (AMI). The purpose of this study is to evaluate whether streptokinase (SK) therapy prevents LVT, and whether this effect is due to the preservation of left ventricular function or to the fibrinolytic action of the drug. Sixty-five patients who underwent a left ventricular angiography within 2 months after a first AMI were studied. Twenty-eight patients (SK group) received SK 1,500,000 U i.v. administered over 60 min within 6 h from the onset of symptoms. A lower incidence of LVT was found in the SK group (p = 0.0003). We divided patients into two classes according to the value of akinetic-dyskinetic area (AD): the first group with a lower value of AD, the second group with a higher value of AD. In both groups, a reduced incidence of LVT was associated with SK therapy (p = 0.014, p = 0.015, respectively). Early infusion of SK during AMI seems to prevent the development of LVT, with an effect partly independent from its action on infarct size for small to large myocardial infarction.

Multiple microemboli after disintegration of clot during thrombolysis for acute myocardial infarction

Seven of 475 consecutive patients treated with thrombolysis for acute myocardial infarction had severe embolic complications that were believed to be caused by disintegration of pre-existing clot. Three patients had symptoms that persisted for many weeks, and five died. Any potential site of pre-existing blood clot within the vascular system, notably an enlarged left atrium, ventricular aneurysm, or aortic aneurysms, should be regarded as a contraindication to treatment with thrombolytic agents.

Pharmacodynamics of thrombolysis with recombinant tissue-type plasminogen activator. Correlation with characteristics of and clinical outcomes in patients with acute myocardial infarction. The TAMI Study Group

Coagulation analysis was performed on blood samples from 386 patients with acute myocardial infarction drawn before, during, and after a continuous intravenous infusion of 150 mg recombinant tissue-type plasminogen activator (rt-PA) (Activase). Plasma rt-PA rose to peak levels of 2.1 +/- 3.1 micrograms/ml (mean +/- SD). Fibrinogen levels measured by coagulation rate and by sulfite precipitation decreased from baseline levels of 3.0 +/- 0.9 and 3.2 +/- 1.0 g/l, respectively, to nadir levels of 1.4 +/- 0.75 and 1.8 +/- 0.92 g/l, respectively, and were associated with peak levels in serum of fibrinogen-degradation products (FDP) of 230 +/- 470 micrograms/ml. Forty percent of patients experienced a nadir functional-fibrinogen level of less than 1.0 g/l, whereas 20% fell below 0.5 g/l. Nadir fibrinogen levels did not correlate with patency of the infarct-related coronary artery at 90 minutes or with risk of coronary vessel reocclusion within 7-10 days. However, the risk of coronary artery reocclusion was inversely related to the baseline functional fibrinogen level (p = 0.0008), with the magnitude of its drop to nadir level (p = 0.0003) as well as to peak levels of FDP (p = 0.038). Quantitative blood loss correlated with all markers for systemic fibrinogenolysis including nadir fibrinogen level (r = -0.20, p = 0.0011), percent decrease of fibrinogen (r = 0.22, p = 0.001), and peak FDP levels (r = 0.14, p = 0.020). Both patients who experienced intracranial hemorrhage presented with high baseline fibrinogen levels and experienced extensive degradation of coagulable fibrinogen. Overall, patients at greatest risk of systemic fibrinogenolysis tended to be relatively older women with lower body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics, thrombolytic efficacy and hemorrhagic risk of different streptokinase regimens in heparin-treated acute myocardial infarction

The systemic activator activity of 4 streptokinase (SK) regimens (250,000 IU intracoronary, group A; 500,000 IU, group B; 1.5 X 10(6) IU, group C; and 30 U anisoylated plasminogen streptokinase activator complex (APSAC) intravenously, group D) was tested with the fibrin plate technique. One hour after initiation of treatment, the activator activity was highest after APSAC (3.6 +/- 0.9 U), slightly but not significantly less after SK 1.5 X 10(6) IU (3.0 +/- 0.7), and significantly less after SK 500,000 IU (1.6 +/- 0.5) and 250,000 IU (0.6 +/- 0.5), p less than 0.001. After SK, activator activity half-lives were 184 minutes (group B) and 169 minutes (group C), and after APSAC 188 minutes (group D). These were all in agreement with greater than 12 hour duration of changes in other markers of systemic fibrinolysis (euglobulin lysis time) and substrates depletion (fibrinogen, plasminogen, alpha 2 antiplasmin). In extended pilot clinical groups given identical thrombolytic regimens during full anticoagulation with heparin, angiographic coronary patency was found in 83% (35 of 42) after intracoronary SK (group 1), in 73 and 75%, respectively, after 500,000 IU (31 of 43) and 1.5 X 10(6) IU (30 of 40) (group 2 and 3, difference not significant) and 80% (8 of 10) after the 30-U bolus of APSAC (group 4). The overall hemorrhagic risk was 24%, equally distributed among the 4 regimens and mostly (91%) related to catheters. The incidence of bleeding unrelated to vessel puncture was 4%; no deaths occurred. It is concluded that APSAC is the most fibrinolytic regimen but its potential thrombolytic superiority over SK remains to be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Low dose urokinase preactivated natural prourokinase for thrombolysis in acute myocardial infarction

By inducing minimal free-fibrinolytic activity with low dose urokinase, the lag phase of prourokinase can be overcome, and the rate of thrombolysis with this substance can be strongly enhanced. The thrombolytic potency of a combination of 250,000 IU of urokinase and 2 doses of prourokinase (4.5 or 6.5 megaunits) was evaluated in an open-label, nonrandomized dose-finding study. Thirty-one patients participated. With 4.5 megaunits of prourokinase (group 1, 15 patients) patency was demonstrated angiographically at 60 minutes in 33% while with 6.5 megaunits (group II, 16 patients) 75% patency was achieved (p less than 0.01). A second angiogram recorded 24 to 36 hours after thrombolysis revealed reocclusion in 60 versus 8% of primarily patent coronary arteries (p less than 0.05). Hemostatic monitoring in both groups revealed only slight to moderate consumption of fibrinogen (-9 vs -13%), plasminogen (-29 vs -34%) and alpha 2-antiplasmin (-59 vs -63%), and an increase in D-dimers, the split products of cross-linked fibrin, to a maximum of 1.008 +/- 1.211 vs 0.547 +/- 0.684 micrograms/liter. None of these differences was significant. Bleeding complications were more frequently observed in group II (13 vs 37%) (difference not significant), but were mild and related to puncture sites, except in 1 patient with mild oozing from the gum. No major hemorrhage was observed. These results suggest that low dose urokinase preactivation enhances the thrombolytic potency of prourokinase, without affecting its high fibrin specificity. Compared to previous studies using only prourokinase, low dose urokinase preactivation reduces by 50% the prourokinase dose as required for effective thrombolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Do different doses of intravenous streptokinase alter the frequency of coronary reperfusion in acute myocardial infarction?

This study assessed the relative efficacy of 3 doses of intravenous streptokinase in causing hypofibrinogenemia and coronary reperfusion in patients with acute myocardial infarction. Accordingly, 56 patients (50 men and 6 women, ages 58 +/- 10 years [mean +/- standard deviation]) with evolving acute myocardial infarction and chest pain less than or equal to 5 hours in duration were assigned to receive varying doses of streptokinase. Twenty were administered 500,000 units during 145 minutes, 18 were given 750,000 units during 30 minutes and 18 received 1.5 million units in 60 minutes of streptokinase. Serum creatine kinase was measured on admission and 6, 12, 18 and 24 hours after the initiation of streptokinase. The time intervals from onset of pain to peak creatine kinase and from streptokinase administration to peak creatine kinase were used to determine the occurrence of reperfusion. The plasma fibrinogen concentration was measured 30, 60, 90 and 120 minutes after the initiation of streptokinase. For the 3 groups, the time from onset of pain to peak creatine kinase was less than 17 hours and the time from streptokinase to peak creatine kinase was 6 or 12 hours in 15 (75%), 16 (89%) and 12 patients (67%), respectively (differences not significant). The plasma fibrinogen concentration decreased to 45 +/- 34 mg/dl, 19 +/- 14 mg/dl and 29 +/- 43 mg/dl, respectively, during the 2 hours after streptokinase was begun (p less than 0.05 for the first versus the second and third values).(ABSTRACT TRUNCATED AT 250 WORDS)

Ancrod enhances the thrombolytic effect of streptokinase and urokinase

Since thrombi continue to incorporate fibrin during lysis we tested the effect of pretreatment with ancrod, a defibrinating agent from Malaysian pit viper venom, on thrombolysis with urokinase and streptokinase. Thrombi were induced by copper-coils in the carotid arteries of the dogs, weighed after 1 hour and inserted into the femoral arteries of the same animals. They were then exposed for 15 min to iv boluses of streptokinase 10,000 U/kg, urokinase 10,000 U/kg and urokinase 25,000 U/kg with or without pretreatment with ancrod. Ancrod depleted fibrinogen within 5 min and enhanced the lytic effect of streptokinase from 25 +/- 8% to 59 +/- 13% (p less than .05), urokinase 10,000 U/kg from 16 +/- 11% to 66 +/- 18% (p less than .01) and urokinase 25,000 U/kg from 27 +/- 17% to 85 +/- 8% (p less than .001) of the initial thrombus weight. Ancrod itself did not activate plasminogen to plasmin. We conclude that ancrod enhances thrombolysis probably by depleting fibrinogen and preventing new fibrin incorporation into the thrombus during lysis.