Prevention of coronary artery reocclusion and reduction in late coronary artery stenosis after thrombolytic therapy in patients with acute myocardial infarction. A randomized study of maintenance infusion of recombinant human tissue-type plasminogen activator

Endothelial dysfunction after arterial thrombosis is ameliorated by L-arginine in combination with thrombolysis

PURPOSE

To assess endothelial function after arterial thrombosis creation and after administration of a novel thrombolytic regimen in a new porcine model.

MATERIALS AND METHODS

Untreated arteries that had undergone thrombosis for 90 minutes were compared to arteries treated with tissue plasminogen activator (tPA, 4 mg) and a combination of tPA and L-arginine (L-arg; 600 mmol/L). External iliac artery luminal diameter was measured with use of duplex ultrasonography. Endothelial-dependent relaxation (EDR) and endothelial-independent relaxation (EIR) were measured with use of acetylcholine chloride (ACh) and sodium nitroprusside (NTP), respectively. Endothelial integrity was confirmed by scanning electron microscopy (SEM). Nitric oxide (NO) levels were determined with use of a chemiluminescent assay of its nitrite/nitrate metabolites (NO(x)).

RESULTS

After thrombosis, EDR was decreased (69% +/- 9.5; ACh = 15 micro g/min; n = 6). EDR remained unchanged after thrombolysis with tPA despite complete dissolution of thrombus (67% +/- 5.7; ACh = 15 micro g/min; n = 5). Thrombolysis with use of tPA coupled with L-arg resulted in an increase in EDR (95% +/- 4.9; ACh = 15 micro g/min; n = 5; P =.007). EIR was preserved in all groups, with uniform response to NTP. SEM analysis revealed intact endothelium in all groups. Local NO(x) levels were diminished after 90 minutes of thrombosis (49.3 micro mol/L vs 40.8 micro mol/L; P =.0002), but increased to 55.7 micro mol/L after thrombolysis with tPA and L-arg (P = NS).

CONCLUSIONS

Thrombus induces arterial dysfunction acutely without altering endothelial integrity. This dysfunction is ameliorated through regional administration of L-arg in combination with standard thrombolytic therapy, which increases local NO levels. This model allows the in-vivo study of thrombosis and alternative thrombolytic regimens. Regional enhancement of NO levels may prove to be an attractive adjunct in thrombolytic therapy.

Improving the Efficacy and Stability of Coronary Reperfusion Following Thrombolysis: Exploring the Thrombin Hypothesis

A major assumption in the treatment of patients with acute myocardial infarction (MI) implies that the speed of coronary arterial reperfusion correlates directly with the overall extent of myocardial salvage, and that the extent of mycardial salvage, in turn, determines the absolute reduction in patient mortality. While a growing experience has made it clear that myocardial salvage-independent (time-independent) mechanisms of benefit also exist, few would argue with the hypothesis that the greatest benefit derived from coronary thrombolysis occurs with early (time-dependent) treatment. Thus, improvements in the efficacy of reperfusion and the stability of reperfusion are likely to have considerable impact on patient outcome.

Significance of the Thrombolysis in Myocardial Infarction scoring system in assessing infarct-related artery reperfusion and mortality rates after acute myocardial infarction

Thrombolysis in Myocardial Infarction (TIMI) flow scores were originally devised as semiquantitative angiographic measures of coronary artery perfusion. Several studies have indicated an important relation between different TIMI flow grades at 90 minutes after thrombolysis and clinical outcome. To further evaluate this relation we conducted a metaanalysis of all angiographic, postinfarction trials that studied the relation between individual 90-minute TIMI flow grades and mortality rates. In 4687 pooled patients, the mortality rate was lowest in patients with TIMI grade 3 flow (3.7%) and significantly lower than those with TIMI 2 (6.6%, p = 0.0003; odds ratio 0.55; 95% confidence interval [CI] 0.4% to 0.76%) or TIMI 0/1 flow (9.2%, p < 0.0001; odds ratio 0.38; 95% CI 0.29% to 0.5%). The mortality rate difference between TIMI grade 2 and TIMI grade 0/1 patients was also significant (p = 0.02; odds ratio 0.7; 95% CI 0.51% to 0.94%). This study confirms the importance of achieving rapid and complete reperfusion after acute myocardial infarction with the best outcome associated with 90-minute TIMI 3 flow. Furthermore, it shows that although TIMI 2 flow (partial perfusion) is not equivalent to TIMI 3 flow, it nevertheless still confers a significant survival benefit compared with TIMI flow 0/1.

TIMI grade 3 flow and reocclusion after intravenous thrombolytic therapy: a pooled analysis

Early and sustained flow of grade 3 according to Thrombolysis in Myocardial infarction (TIMI) criteria and reocclusion rates are the key measures that define the physiologic efficacy of thrombolytic agents in the treatment of acute myocardial infarction. We performed a systematic overview of angiographic studies after intravenous thrombolysis with accelerated and standard-dose tissue-plasminogen activator (TPA), anisoylated plasminogen streptokinase activator complex (APSAC), and streptokinase. There were 5475 angiographic observations from 15 studies for TIMI flow analysis and 3147 angiographic observations from 27 studies for reocclusion. At 60 and 90 minutes, the rates of TIMI grade 3 flow were 57.1% and 63.2%, respectively, with accelerated TPA, 39.5% and 50.2% with standard-dose TPA, 40.2% and 50.1% with APSAC, and 31.5% at 90 minutes with streptokinase. Overall reocclusion with standard-dose TPA was 11.8% versus 6.0% for accelerated TPA, 4.2% for streptokinase, and 3.0% for APSAC. Although the incidence of TIMI grade 3 flow increased over time with all thrombolytic regimens, decreased patency was observed at 180 minutes with accelerated TPA. Still, accelerated TPA is the most effective agent to establish early (90-minute) TIMI grade 3 flow.

Comparative study of a mutant tissue-type plasminogen activator, YM866, with a tissue-type plasminogen activator in a canine model of femoral arterial thrombosis

Because tissue-type plasminogen activator (tPA), used to treat myocardial infarction, has several disadvantages thought to be connected with its low half-life, mutants of tPA have been prepared with longer half-lives. We have compared the thrombolytic effect of such a mutant, YM866, with that of tPA in copper-coil-induced femoral arterial thrombosis in dogs. One hour after thrombus formation, YM866 was administered by intravenous bolus injection, while tPA was given by the same method or by 60-min infusion under adequate heparinization. Both agents exhibited dose-dependent thrombolysis without systemic fibrinogenolysis. The recanalization rate and recanalization time of YM866 by bolus at 0.2 mg kg-1 were, however, equivalent to those of tPA by infusion at 0.4 mg kg-1 (total dose), whereas the recanalization rate of tPA by bolus was low (0.4 mg kg-1). No significant difference in reocclusion rate, reocclusion time, or patency status after successful thrombolysis was seen. These results suggest that YM866 administered at a lower dose by intravenous bolus injection exerted a thrombolytic effect equivalent to that of tPA by infusion, and that heparin could not prevent reocclusion after successful thrombolysis even under adequate anticoagulation.

Antithrombotic effect of GYKI-14766 in a canine model of arterial and venous rethrombosis: a comparison with heparin

We compared the antithrombotic effects of the thrombin inhibitor, D-methyl-phenylalanyl-prolyl-arginal (GYKI-14766) with those of heparin in a canine model of arterial and venous rethrombosis. Thrombogenesis was induced by electrolytic injury to the endothelial surface of the carotid artery and jugular vein. Either heparin (300 U/kg, n = 7), GYKI-14766 (0.5 mg/kg/h, n = 7), or saline (n = 10) was administered intravenously (i.v.) immediately after the local administration of anisoylated plasminogen streptokinase activator complex (APSAC 0.1 U/kg). Supplemental doses of heparin (100 U/kg) were administered at 1-h intervals. Infusion of GYKI-14766 was maintained for 5 h throughout the experiment. Ex vivo platelet aggregation in response to ADP or arachidonic acid (AA) was not changed in any of the experimental groups. Both GYKI-14766 and heparin increased the activated partial thromboplastin time (aPTT) over their respective baseline values. Heparin, but not GYKI-14766, increased the bleeding time. After successful thrombolysis, arterial and venous rethrombosis occurred in all saline-treated dogs. GYKI-14766 prevented cyclic flow variations and reocclusion in the artery and the vein (p < 0.01). Heparin had only minimal effects on the artery and no effect on the vein. Arterial thrombus weights were reduced by GYKI-14766 [saline control = 24 +/- 4 mg, GYKI-14766 = 9 +/- 3 mg, (p < 0.05); heparin = 14 +/- 2 mg, p = NS]. The venous thrombus weights were reduced slightly by GYKI-14766 and were unchanged by heparin (saline = 25 +/- 5 mg, GYKI-14766 = 13 +/- 4 mg, heparin = 26 +/- 3 mg). The data suggest that GYKI-14766 is effective in preventing occlusive rethrombosis in both the arterial and venous circulation after thrombolysis without augmenting bleeding time. GYKI-14766 may represent an alternative to heparin as an adjunctive agent during thrombolytic therapy.

Concurrent nitroglycerin administration reduces the efficacy of recombinant tissue-type plasminogen activator in patients with acute anterior wall myocardial infarction

The aim of this study was to evaluate the impact of concurrent nitroglycerin administration on the thrombolytic efficacy of recombinant tissue-type plasminogen activator (rTPA) in patients with acute anterior myocardial infarction (AMI). Sixty patients (53 men, 7 women; mean age 54 +/- 7 years) with AMI entered the study. Thirty-three patients were randomized to receive rTPA alone (100 mg in 3 hours) (group A) and 27 to receive rTPA plus nitroglycerin (100 micrograms/min) (group B). Time from the onset of chest pain and delivery of rTPA was similar in the two groups of patients. Patients in group A had signs of reperfusion more often than the patients in group B (25 of 33 or 75.7% vs 15 of 27 or 55.5%, p < 0.05). Time to reperfusion was also shorter in group A than in group B (19.6 +/- 9.4 minutes vs 37.8 +/- 5.9 minutes, p < 0.05). Group B had a greater incidence of in-hospital adverse events (9 of 27 vs 5 of 33, p < 0.05) and a higher incidence of coronary artery reocclusion (8 of 15 or 53.3% vs 6 of 25 or 24%, p < 0.05). Peak plasma levels of rTPA antigen were higher in group A compared with group B (1427 +/- 679 vs 512 +/- 312 ng/ml, p < 0.01). In conclusion, concurrent nitroglycerin administration reduces the thrombolytic efficacy of rTPA in patients with AMI probably by lowering the plasma levels of rTPA antigen. The diminished efficacy of rTPA is associated with an adverse outcome.

Experimental studies on preventive effects of API0134 on vessel reocclusion after thrombolysis

24 model rabbits with femoral arterial thrombosis were divided into two groups: the treatment group consisting of 12 rabbits which received API0134, and the control group composed of another 12 rabbits. 2 hours after recanalization by urokinase thrombolysis, reocclusion occurred only in 1/12 vessel (8%) with incomplete occlusion in the treated group, but in 8/12 (67%) with complete occlusion in the control group as assessed by angiograsphy. Pathological examination of specimen taken 24 hours after thrombolysis showed that 6/12 (50%) of the treated group gave the evidence of thrombus occlusion, and milder intimal injury and less adhered blood cells than in the control group, 83% of which had thrombus occlusion. In comparision with the control group, the function of platelet in the treated group demonstrated lower platelet aggregation rate (PAgR) and plasma thromboxane A2 (TXA2) level, higher prostacyclin (PGI2) and plasminogen activator (PA) activity as well as lower plasminogen activator inhibitor (PAI) activity. From the above it may be concluded that the preventive effect of API0134 on reocclusion might be due to inhibition of platelets aggregation and promotion of fibrinolysis.

A pooled analysis of coronary arterial patency and left ventricular function after intravenous thrombolysis for acute myocardial infarction

Individual studies of patency rates and left ventricular (LV) function after thrombolysis have generally been limited by small numbers of observations, wide confidence intervals, and limited numbers of time points. To obtain a more reliable estimate of patterns of patency and LV ejection fraction, a systemic overview of angiographic studies was performed after intravenous thrombolytic therapy. A total of 14,124 angiographic observations from 58 studies evaluating patency after no thrombolytic agent, streptokinase, standard dose tissue-type plasminogen activator (t-PA), accelerated dose t-PA, or anistreplase (anisoylated plasminogen streptokinase activator complex [APSAC]) were included. At 60 and 90 minutes, streptokinase had the lowest patency rates of 48% and 51%, respectively, standard dose t-PA and APSAC had similar intermediate rates of approximately 60% and 70%, and accelerated t-PA had the highest patency rates of 74% and 84%. By 2 to 3 hours and longer, the patency rates were similar for the various regimens. Reocclusion rates in studies including 1,172 patients randomized to t-PA versus a nonfibrin-specific agent were higher after t-PA (13.4% vs 8.0%, p = 0.002). Ten studies enrolling 4,088 patients treated with thrombolytic therapy versus control demonstrated a modest improvement in mean LV ejection fraction in the thrombolytic group at each of the times after thrombolytic therapy: hour 4, day 1, day 4, day 7 to 10, and day 10 to 28 after thrombolysis. By 4 days, mean ejection fraction was 53% versus 47% (thrombolytic vs control therapy, p < 0.01); by 10 to 28 days it was 54.1% and 51.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Laser thrombolysis in acute myocardial infarction: results of a clinical feasibility study

Laser thrombolysis is a new, experimental, catheter based intervention aimed at selectively removing intracoronary thrombus. This first clinical study was performed to assess the feasibility and safety of laser thrombolysis, as well as its potential therapeutic place in acute myocardial infarction. Eighteen patients with acute myocardial infarction, who were either noncandidates for, or failures on, intravenous fibrinolytic therapy were included for treatment with laser thrombolysis followed by balloon angioplasty. As a result of catheter and technical failures, the laser was actually fired in only 12 patients. Improvement in TIMI flow from grade 0-1 to grade 2-3 was observed in 10 of these 12 patients after laser application. The overall results of 18 patients were: increase in TIMI grade flow from 0.33 +/- 0.49 after wire passage to 1.28 +/- 1.23 (P = 0.0051) after attempted laser application, and to 2.67 +/- 0.97 after PTCA (P = 0.0004). Two patients with previous infarctions died from left ventricular failure despite successful laser thrombolysis. One patient died during emergency bypass surgery after a failed recanalization attempt. Perforation or laser related dissection did not occur. The concept of selective laser thrombus ablation seems to be safe and feasible, but substantial improvements of the laser delivery catheters are needed. Laser thrombolysis is not an effective stand-alone therapy in acute myocardial infarction, but other possible applications warrant further research and development efforts for this potentially useful interventional tool.

Cyclic flow variations after coronary angioplasty in humans: clinical and angiographic characteristics and elimination with 7E3 monoclonal antiplatelet antibody

OBJECTIVES

We tested the hypothesis that cyclic alterations in coronary artery blood flow that occurred after coronary angioplasty could be attenuated or abolished by a monoclonal antibody to the platelet surface membrane GP IIb/IIIa receptor.

BACKGROUND

Coronary artery cyclic flow variations may occur after coronary angioplasty in experimental animal models and humans. In animal models of coronary thrombosis, cyclic alterations in flow often have preceded thrombotic occlusion or reocclusion. Several agents that inhibit platelet function have been shown to attenuate or eliminate cyclic flow variations in these models.

METHODS

We monitored coronary artery flow in 27 patients for 30 min after coronary angioplasty, using 0.018-in. (0.046 cm) coronary guide wires with pulsed wave Doppler ultrasound transducers on the distal tips. Clinical data were collected and quantitative analyses performed on coronary arteriograms made before and after the angioplasty procedures. We compared findings in patients with and without cyclic flow variations detected.

RESULTS

There were 20 men and 7 women. Mean age was 58 years, and 63% had unstable angina. They received standard doses of nitrates, aspirin, heparin, calcium channel antagonists and other medications clinically indicated. Nevertheless, we detected cyclic flow variations in five patients (19%). Four of these patients had stable flow restored with intravenous injection of 0.25 mg/kg normal body weight of monoclonal antibody c7E3 Fab to the platelet GP IIb/IIIa receptor. In one patient, stable flow was restored by repeat dilation when an immediate angiogram revealed renarrowing. Patients developing cyclic alterations in flow had longer lesions (18.7 +/- 7.5 mm vs. 13.1 +/- 5.7 mm, p < 0.05) that had responded less well to angioplasty (stenosis postangioplasty 47 +/- 13% vs. 33 +/- 15%, p < 0.05).

CONCLUSIONS

Cyclic alterations in coronary artery blood flow may occur in some patients after coronary angioplasty, despite the use of standard antiplatelet, antithrombotic and antivasospastic medications. We found that they could be eliminated by this monoclonal antibody that blocks the final common event of platelet aggregation.

Time course of the effects of a single bolus injection of F(ab')2 fragments of the antiplatelet GPIIb/IIIa antibody 7E3 on arterial eversion graft occlusion, platelet aggregation, and bleeding time in dogs

The time course of the effects of a single intravenous bolus injection of 10 mg/kg aspirin or 0.8 mg/kg F(ab')2 fragments of the monoclonal antiplatelet glycoprotein IIb/IIIa receptor antibody 7E3 [7E3-F(ab')2] on arterial occlusion, platelet aggregation, and bleeding time was studied in 30 dogs with an everted (inside out) carotid arterial segment inserted into the femoral artery. In the absence of an antiplatelet agent, the eversion grafts occluded spontaneously with platelet-rich thrombus within 30 minutes. With aspirin, arterial occlusion persisting for 2 hours occurred in 5 of 10 dogs and cyclic occlusion and reflow in 4 animals; arterial occlusion was observed in all dogs at 24 hours. With 7E3-F(ab')2, arterial patency persisted throughout a 2-hour observation period in all of 10 dogs and for 24 hours in 4 of the 10 dogs. Contralateral eversion grafting 24 hours after aspirin or 7E3-F(ab')2 injection was associated with graft patency for 2 hours in 1 of 5 aspirin dogs and in 3 of 5 7E3-F(ab')2 dogs; patency persisted for 24 hours. In dogs grafted 48 hours after aspirin or 7E3-F(ab')2 injection, patency at 24 hours was seen in 0 of 5 dogs given aspirin and 3 of 5 dogs given 7E3-F(ab')2. The overall frequencies of arterial graft patency at 2, 24, 48, and 72 hours after study drug injection were significantly higher in the 7E3-F(ab')2 groups than in the aspirin groups (P < .0005, n = 10 in each group; P < .05, n = 15; P < .005, n = 15; and P = .05, n = 5, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of inclusion of patients with cardiogenic shock in trials of thrombolytic therapy

The purpose of this study was to determine the extent to which patients with cardiogenic shock have participated in trials of thrombolytic therapy, to examine factors associated with their exclusion from these trials, and to summarize data on the efficacy of thrombolysis in these patients. Previous publications were searched for all randomized, controlled studies involving the use of thrombolytic medications used in the treatment of acute myocardial infarction. Data were abstracted for year of trial publication, performance location, sample size, maximal allowable delay between symptom onset and treatment, and exclusion criteria. Of the 94 trials included in the analysis, 22% included patients with cardiogenic shock, 37% excluded them, and the remainder contained no information on their inclusion or exclusion. Only 2 trials provided data on the efficacy of thrombolytic therapy in patients with cardiogenic shock. Multivariate analysis revealed that studies conducted exclusively in the U.S. were significantly more likely to exclude patients in cardiogenic shock than those conducted outside of the U.S., as were studies that excluded patients with a previous myocardial infarction, studies published more recently, and smaller trials. Patients with cardiogenic shock have frequently been excluded from clinical trials of thrombolytic agents. As a result, data on the efficacy of thrombolytic agents in these patients is extremely limited.

Antiplatelet and antithrombotic efficacy of DMP 728, a novel platelet GPIIb/IIIa receptor antagonist

BACKGROUND

Currently used antiplatelet drugs, including aspirin, ticlopidine, and others, are effective against certain but not all of the many endogenous platelet activators. Because of their limited efficacy, a significant number of serious thromboembolic complications still occur, highlighting the need for a more effective therapy. Thus, we have identified a systemically active peptide analogue (DMP 728) of the arginine-glycine-aspartic acid (RGD) recognition sequence that mediates the binding of ligands such as fibrinogen to the platelet glycoprotein (GP) IIb/IIIa receptors. The goals of the present study were to determine the antiplatelet and antithrombotic efficacies of DMP 728 in various arterial thrombosis models.

METHODS AND RESULTS

DMP 728 demonstrated antiplatelet efficacy in vitro in inhibiting ADP-induced human platelet aggregation (IC50, 46 +/- 2 nmol/L) and fibrinogen binding to human platelets (IC50, 2.3 +/- 0.8 nmol/L) or purified human GPIIb/IIIa receptors (IC50, 0.6 +/- 0.1 nmol/L). DMP 728 demonstrated high affinity and specificity for human platelet GPIIb/IIIa over other adhesion molecules. In anesthetized mongrel dogs, DMP 728 at 0.001 to 1.0 mg/kg IV produced dose-dependent antiplatelet effects in inhibiting ex vivo platelet aggregation induced by ADP and in prolonging template bleeding time. DMP 728 effects on bleeding time prolongation were more rapidly reversible than those on platelet aggregation inhibition. A maximal antiplatelet effect for DMP 728 was demonstrated at 0.01 mg/kg IV bolus. The antithrombotic efficacy of DMP 728 was examined in vitro and in vivo after IV administration at different doses in various models of arterial thrombosis. In the coronary artery Folts model in dogs, DMP 728 demonstrated maximal antithrombotic efficacy at 0.01 mg/kg IV bolus with an ED50 of 0.005 mg/kg IV bolus in inhibiting cyclic flow reductions. Additionally, DMP 728 demonstrated 100% prevention of primary thrombosis and rethrombosis (P < .01) after treatment with different thrombolytics, including tissue plasminogen activator and streptokinase, in an electrolytically induced femoral artery thrombosis model in dogs.

CONCLUSIONS

Acute intravenous DMP 728 administration (0.001 to 1.0 mg/kg) has dose-dependent antiplatelet and antithrombotic effects in different arterial thrombosis models. These data suggest that DMP 728, a low-molecular-weight GPIIb/IIIa receptor antagonist, may have therapeutic potential as an effective antithrombotic agent in coronary and peripheral artery thromboembolic disorders.

Culprit lesion morphology and stenosis severity in the prediction of reocclusion after coronary thrombolysis: angiographic results of the APRICOT study. Antithrombotics in the Prevention of Reocclusion in Coronary Thrombolysis

OBJECTIVES

In the APRICOT study (Antithrombotics in the Prevention of Reocclusion In Coronary Thrombolysis), we sought to determine whether angiographic characteristics of the culprit lesion could predict reocclusion after successful thrombolysis and to analyze the influence of three antithrombotic treatment regimens.

BACKGROUND

After successful thrombolysis, reocclusion is a major problem. Prediction of reocclusion by angiographic data and choice of antithrombotic treatment would be important for clinical management.

METHODS

After thrombolysis, patients were treated with intravenous heparin until initial angiography was performed within 48 h. Patients with a patent infarct-related artery were eligible. Three hundred patients were randomly selected for treatment with coumadin, aspirin (300 mg once daily) or placebo. Patency on a second angiographic study after 3 months was the primary end point of the study.

RESULTS

Reocclusion rate was 25% with aspirin, 30% with coumadin and 32% with placebo (p = NS). Lesions with > 90% stenosis reoccluded more frequently (42%) than did those with < 90% stenosis (23%) (p < 0.01). Reocclusion rate of smooth lesions was higher (34%) than that of complex lesions (23%) (p < 0.05). In lesions with < 90% stenosis, the reocclusion rate was lower with aspirin (17%) than with coumadin (25%) or placebo (30%) (p < 0.01). In complex lesions, the reocclusion rate was lower with aspirin (14%) than with coumadin (32%) or placebo (25%) (p < 0.02). Multivariate analysis showed only stenosis severity > 90% to be an independent predictor of reocclusion (odds ratio 2.31, 95% confidence interval 1.28 to 4.18, p = 0.006).

CONCLUSIONS

Angiographic features of the culprit lesion after successful coronary thrombolysis significantly predict the risk of reocclusion: high grade (> 90%) stenoses reoccluded more frequently. Aspirin was effective only in complex and less severe lesions (< 90% stenosis). These findings should prompt investigation of the effects of an aggressive approach to patients with severe residual stenosis.

Defibrotide versus heparin in the prevention of coronary reocclusion after thrombolysis in acute myocardial infarction

A multicenter controlled study versus heparin was conducted to explore the activity of defibrotide, a polydesoxyribonucleotide drug, in preventing reocclusion after urokinase thrombolysis in patients with acute myocardial infarction (AMI). The study involved 137 consecutive patients with AMI and a time from the onset of symptoms < or = 6 hours, treated with urokinase (1,000,000 U intravenous bolus followed by 1,000,000 U slow-drip infusion over 12 hours). Immediately after thrombolysis, patients were allocated to treatment with defibrotide (group D: day 0, 3.6 g by intravenous infusion in 12 hours; days +1 to +6, 800 mg tid intravenously; days +7 to +10/+12, 400 mg tid intramuscularly), or heparin (group H: day 0, 1000 IU/hour infused over 12 hours; days +1 to +10/+12, 5000 IU tid subcutaneously). Coronary angiography was done, whenever possible, at +10/+12 days. The following parameters were assessed: (a) noninvasive estimate of myocardial reperfusion, through the analysis of CPK time-activity curves; (b) incidence of infarct-related artery (IRA) patency (TIMI scores 2-3) at coronary angiography. A total of 125 patients had a complete enzymatic curve (63 in group D and 62 in group H) and 106 had coronary angiography as well. IRA patency (the main end point) was observed in 63% of group D versus 43% of group H patients (p = 0.07). No statistically significant differences were found in the proportion of patients with indirect signs of early reperfusion (63% in group D versus 52% in group H patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Maintenance of patency after thrombolysis in stenotic coronary arteries requires combined inhibition of thrombin and platelets

OBJECTIVES

This study was designed to determine whether maintenance of patency in coronary arteries with high grade stenosis after thrombolysis with tissue-type plasminogen activator requires inhibition of thrombin or platelets, or both.

BACKGROUND

Activation of both thrombin and platelets has been implicated in delaying coronary recanalization induced with fibrinolytic drugs and in predisposing to reocclusion.

METHODS

Hirudin (1.5 mg/kg body weight) or aspirin (5 mg/kg), or both, was given conjunctively with tissue-type plasminogen activator in 28 conscious dogs with coronary thrombosis induced by electrical stimulation of the vessel wall in the presence of a previously placed high grade distal stenosis (85 +/- 12% [SEM] area reduction).

RESULTS

Among 22 dogs exhibiting coronary recanalization, hirudin plus aspirin, but neither agent alone, modestly shortened the interval to recanalization (31 +/- 4 min with saline solution, n = 6; 29 +/- 4 min with aspirin, n = 5; 23 +/- 9 min with hirudin, n = 6; 21 +/- 7 min with hirudin+aspirin, n = 5). Reocclusion occurred promptly and persisted in five of six dogs given only saline solution plus tissue-type plasminogen activator, in four of six dogs given hirudin and five of five dogs given aspirin; however, reocclusion was prevented in all five of the dogs given both hirudin and aspirin with tissue-type plasminogen activator (p < 0.05 compared with saline-treated dogs). In dogs given both hirudin and aspirin, the partial thromboplastin time was 2.4 +/- 0.3 times baseline, and the template bleeding time was prolonged only modestly (1.6 +/- 0.3 times baseline).

CONCLUSIONS

Thus, the combination of hirudin and aspirin in doses that do not markedly perturb hemostasis prevents early reocclusion after thrombolysis despite the presence of severe stenosis. Accordingly, conjunctive administration of both anti-thrombin and antiplatelet agents appears to be necessary for optimal maintenance of patency after thrombolysis induced in the presence of high grade coronary stenosis.

Dose-ranging study with a new two-chain rt-PA in patients with acute myocardial infarction: a multicenter trial

Tissue-type plasminogen activator (t-PA) derived from a melanoma cell line was first used in patients with acute myocardial infarction in the early 1980s. Recombinant DNA technology then allowed production of large amounts of t-PA. The TIMI-I trial used a two-chain recombinant (rt-PA) product. A predominantly single-chain rt-PA (alteplase) was used in the majority of the TIMI II trial. The present study used a different form of two-chain rt-PA (duteplase) to determine the effective dose for thrombolysis at 60 min, and to evaluate time to reperfusion, reocclusion at 72-96 h, coagulation profiles, and bleeding events. Duteplase was given intravenously to 75 patients a mean of 3.8 +/- 1 h after the onset of myocardial infarction. Following angiography demonstrating coronary occlusion, 23 patients received a low dose of duteplase [0.16-0.29 million international units per kilogram (MIU/kg)] over 60 min followed by a 5-h infusion in conjunction with heparin, 25 patients received a middle dose (0.30-0.41 MIU/kg) and 23 patients received a high dose (0.43-0.74 MIU/kg). Angiography was then performed every 15 min x 4. Progressive recanalization occurred over 60 min (median 45 min) with an overall success rate of 59% (mean 60-min dose: 0.37 MIU/kg). No dose-response relationship was observed. The reocclusion rate was 9% at 72-96 h. Reductions in fibrinogen and plasminogen correlated with dose, but clinical events did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Cilostazol, a novel cyclic AMP phosphodiesterase inhibitor, prevents reocclusion after coronary arterial thrombolysis with recombinant tissue-type plasminogen activator

Inhibitors of cyclic nucleotide phosphodiesterase hydrolysis of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate are known to inhibit platelet aggregation, which plays an important role in acute reocclusion after thrombolysis in acute myocardial infarction. In the present study of a canine preparation of coronary artery thrombosis superimposed on high-grade stenosis, we tested whether the antithrombotic agent cilostazol, an inhibitor of cAMP phosphodiesterase, could prevent acute reocclusion or sustain coronary blood flow after thrombolysis when used with recombinant tissue-type plasminogen activator (rt-PA) and heparin. Intravenous infusion of rt-PA (0.5 mg/kg body wt for 30 minutes) and heparin (a 150 IU/kg body wt i.v. bolus and then 25 IU/kg body wt per hour i.v.) was combined with cilostazol (0.6 or 1.8 mg/kg body wt for 60 minutes). Without cilostazol, reperfusion was observed in seven of eight dogs, but reocclusion occurred in six of these seven dogs after 9 +/- 2 minutes. After administration of 1.8 mg/kg body wt cilostazol (group B-2; a 120-minute observation after the start of rt-PA infusion), reperfusion occurred in all seven dogs (p < 0.05 versus control group), and brief cyclic reocclusion was observed in only one dog 63 minutes after reperfusion. At the same dose of cilostazol (group B-2L; a 240-minute observation after the start of rt-PA infusion), reperfusion occurred in all five dogs (p < 0.05 versus control group), and coronary blood flow was well maintained except for one short reocclusion in one dog. Cilostazol inhibited cyclic flow reduction in a dose-dependent fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Retreatment with alteplase for early signs of reocclusion after thrombolysis. The European Cooperative Study Group

Recurrent chest pain with new ST-segment elevation was observed in 26 of 652 patients (4%) with myocardial infarction in a clinical trial of alteplase (recombinant tissue-type plasminogen activator; 100 mg) and aspirin with or without heparin. Clinical and electrocardiographic signs of reocclusion were treated with a second dose of alteplase: 50 mg in 20 patients with signs of reocclusion < or = 24 hours after initial therapy, and 100 mg in 5 patients with signs between 24 and 77 hours, and in 1 patient with early signs of reocclusion. Pain and ST changes disappeared within 100 minutes (median 50). D-dimer determinations in 15 patients were increased, indicating activation of the coagulation system. Signs of reocclusion occurred despite adequate anticoagulation with heparin in 5 of 11 patients in whom coagulation measurements were available. No excess bleeding was observed in patients who received a second dose of alteplase. Retreatment with alteplase is feasible and provides an alternative for angioplasty in patients with clinical and electrocardiographic signs of reocclusion early after thrombolytic therapy.

The antithrombotic effect of low molecular weight synthetic thrombin inhibitors, argatroban and PPACK, on He-Ne laser-induced thrombosis in rat mesenteric microvessels

The antithrombotic effect of low molecular weight synthetic thrombin inhibitors, argatroban ((2R, 4R)-4-methyl-1-[N2-[(3-methyl-1, 2, 3, 4-tetrahydro-8-quinolinesulfonyl)-L-arginyl]-2-piperidinecarbox ylic acid monohydrate]) and PPACK (D-phenylalanyl-L-prolyl-L-arginyl-chloromethyl ketone) on He-Ne laser-induced thrombosis in rat mesenteric microvessels was studied. Both inhibitors showed a significant antithrombotic effect at 0.5 mg/kg which lasted for 50 min and 50-60 min using argatroban and PPACK, respectively. A dose-dependent effect was observed in arterioles and venules. The results suggest that thrombin plays an important role in the formation of a platelet thrombus in vivo.

Mechanism of benefit of combination thrombolytic therapy for acute myocardial infarction: a quantitative angiographic and hematologic study

OBJECTIVES

The goal of this study was to lend insight into the mechanisms responsible for the beneficial effects of combination thrombolytic therapy.

BACKGROUND

Combination thrombolytic therapy for acute myocardial infarction has been associated with less reocclusion and fewer in-hospital clinical events than has monotherapy.

METHODS

Infarct-related quantitative coronary dimensions and hemostatic protein levels were evaluated in 287 patients with acute myocardial infarction during the early (90-min) and convalescent (7-day) phases after administration of recombinant tissue-type plasminogen activator (rt-PA), urokinase or combination rt-PA and urokinase.

RESULTS

Minimal lumen diameter was similar in the 90-min and 7-day phases after treatment with rt-PA, urokinase and combination rt-PA and urokinase (0.72 +/- 0.45 mm, 0.62 +/- 0.53 mm and 0.75 +/- 0.58 mm, respectively, at 90 min, p = 0.16; and 1.05 +/- 0.56 mm, 1.12 +/- 0.72 mm and 0.94 +/- 0.54 mm, respectively, at 7 days, p = 0.22). In-hospital clinical event and reocclusion rates were less frequent in patients receiving combination therapy than in those receiving monotherapy (25% vs. 38% and 32% for rt-PA and urokinase, respectively, p = 0.084; and 3% vs. 13% and 9% for rt-PA and urokinase, respectively, p = 0.03), but these events were unrelated to early or late coronary dimensions. Patients receiving combination therapy or urokinase monotherapy had significantly higher peak fibrin degradation products (1,307 +/- 860 and 1,285 +/- 898 micrograms/ml vs. 435 +/- 717 micrograms/ml, respectively, p < 0.0001) and lower nadir fibrinogen levels (0.85 +/- 1.00 and 0.75 +/- 0.53 g/liter vs. 1.90 +/- 0.86 g/liter, respectively, p < 0.0001) than did those receiving rt-PA monotherapy. Peak fibrinogen degradation products indirectly correlated (p = 0.004) and baseline (p = 0.026) and nadir (p = 0.089) fibrinogen levels directly correlated with reocclusion.

CONCLUSIONS

Lower in-hospital clinical event and reocclusion rates observed with combination thrombolytic therapy may relate to systemic hematologic factors rather than to the residual lumen obstruction after thrombolysis.

Influence of the rt-PA dose (1 mg/kg versus 1.5 mg/kg) and duration of administration on the patency of infarct-related coronary arteries in 81 patients

This open study compared the efficacy and side effects of two dose regimens of intravenous rt-PA initiated before the fifth hour after the onset of myocardial infarction. The first 40 patients (group A) received 1 mg/kg of rt-PA infused over 90 minutes, including a 10-mg initial bolus. The following 41 patients (group B) received 1.5 mg/kg (20-mg initial bolus, 60% over 60 minutes and 40% over 120 minutes). Noninvasive clinical, electrocardiographic, and biochemical parameters of reperfusion were recorded systematically, along with serial measurements of fibrinogen and hemoglobin levels. Coronary arteriography and left ventriculography were performed at the 48th hour or earlier, on an emergency basis, in the absence of signs of reperfusion, or if there were clinical and ECG signs of rethrombosis. Patency of the infarct-related artery (TIMI grades 2 and 3) was achieved in 55% of the group A patients vs. 83% of the group B patients (p less than .01). Twelve emergency coronary arteriographies were performed in each group. No significant difference was observed in the ejection fraction (48% in group A vs. 52% in group B). The peak CPK level was similar in both groups, but the peak occurred earlier in group B (p less than .001). There was no statistically significant difference between the two dose regimens in terms of reduction in fibrinogen or plasminogen levels. Two deaths occurred in group A vs. one death in group B. No cerebrovascular accidents occurred in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant tissue plasminogen activator in acute myocardial infarction in the Chinese in Hong Kong

Eighty-nine consecutive Chinese patients (69 males, 20 females) with acute myocardial infarction treated by 100 mg recombinant tissue plasminogen activator (7 intracoronarily, 82 intravenously) at 3.7 +/- 1.0 h after onset, and intravenous heparin or dipyridamole therapy started at 3 h, were studied prospectively. Their mean age was 59.6 +/- 10.6 yr. Forty-six patients (51.7%) had anterior and 39 patients (43.8%) had inferior infarcts. Clinical evidence of reperfusion were seen in 63 patients (70.8%), while new complications included hypotension (5.6%), heart failure (6.7%), cardiac arrhythmias (76.4%) majority of which are related to reperfusion and self-remitting, haematoma around vascular access sites (23.6%), melaena (3.3%) and cerebral infarction (2.2%). Maximal changes in coagulation profiles were seen at 3 h, including a decrease in fibrinogen by 64.2% and an increase in fibrin degradation products by 47 times. The changes in haemostatic variables were not related to body weight or bleeding complications. Nine patients (10.1%) had recurrence of angina and 6 patients (6.9%) died due to pump failure and reinfarction. Angiogram at 14 days confirmed TIMI 2 or 3 patency of infarct-related arteries in 63 out of 73 (86.3%) patients, with a mean global ejection fraction of 52.5 +/- 12.4%. Nearly all survivors could maintain class I-II functional status after discharge. The safety and promise of recombinant tissue plasminogen activator for acute myocardial infarction in the Chinese were confirmed.

Thrombolytic therapy for myocardial ischemia and infarction

Thrombolysis during the early hours of a myocardial infarction significantly improves patient survival in a hospital. Beyond 6 hours, up to 24 hours, thrombolysis may still contribute to a reduction in mortality. However, further confirmation is desirable before such therapy late in the course of an evolving infarct can be routinely recommended. Although clot-specific agents such as recombinant tissue-type plasminogen activator (rt-PA) produce a higher initial patency rate, reocclusion rates are higher in the absence of the profound systemic fibrinolysis produced by agents such as streptokinase. This may explain the GISSI-2 results where 15-day survival was no different between the streptokinase- and rt-PA-treated subjects. Although the manner of heparin administration may have clouded these results, current research is directed toward looking at combinations of thrombolytic agents that would combine drugs efficient in producing early patency with those that produce a more pronounced fibrinolytic state. More effective adjunctive therapy is also under intense investigation, particularly specific antithrombin agents that would produce more effective anticoagulation following thrombolysis, and more effective antiplatelet agents that would help prevent reocclusion.

Acceleration of recombinant tissue-type plasminogen activator-induced reperfusion and prevention of reocclusion by recombinant antistasin, a selective factor Xa inhibitor, in a canine model of femoral arterial thrombosis

Antistasin is a 119-amino acid protein initially isolated from salivary glands of the Mexican leech, Haementeria officinalis, that exhibits potent anticoagulant properties resulting from selective inhibition of blood coagulation factor Xa. The comparative antithrombotic efficacies of recombinant antistasin (rATS), standard heparin (Hep), and aspirin (ASA) administered adjunctly with recombinant tissue-type plasminogen activator (tPA) on thrombolytic reperfusion and reocclusion were determined in a canine model of femoral arterial thrombosis. An occlusive thrombus was formed by insertion of a thrombogenic copper coil into the femoral artery, and blood flow velocity was monitored directly and continuously by Doppler flowmetry. Sixty minutes after occlusion, dogs received an intravenous infusion of either saline (vehicle) or rATS (0.31, 1.25, or 2.5 micrograms/kg/min), intravenous boluses of Hep (100 units/kg + 50 units/kg/hr or 200 units/kg + 150 units/kg/hr), or a single intravenous bolus of ASA (2.0 mg/kg), followed 45 minutes later by tPA (0.8 mg/kg i.v. over 90 minutes). The saline and rATS infusions were discontinued 60 minutes after termination of tPA, and the last Hep boluses were given 105 minutes after termination of tPA. All dogs achieved reperfusion. The time to reperfusion in the ASA group was similar to that in the vehicle group (50 +/- 9 versus 50 +/- 6 minutes, respectively). Reperfusion times were slightly decreased by the low and high doses of Hep (34 +/- 6 and 31 +/- 4 minutes, respectively) and the rATS doses of 0.31 and 1.25 micrograms/kg/min (37 +/- 4 and 36 +/- 5 minutes, respectively). However, the time to reperfusion was dramatically reduced with the 2.5 micrograms/kg/min rATS dose (15 +/- 3 minutes, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a prolonged infusion of recombinant tissue-type plasminogen activator (Duteplase) in preventing reocclusion following successful thrombolysis in acute myocardial infarction

The hypothesis that an infusion of recombinant tissue-type plasminogen activator (rt-PA) maintained for up to 24 hours could prevent reocclusion after early coronary patency had been established was evaluated in patients with acute myocardial infarction. The rt-PA studied was an investigational double chain rt-PA (Duteplase, Burroughs Wellcome Co.), administered according to body weight. Coronary patency was documented in 139 of 213 patients who had 90-minute angiograms recorded after an initial lytic dose of rt-PA. In these responders a further 90-minute infusion at one third the initial lytic dose was given before assignment to 1 of 4 maintenance dose rates (0.012, 0.024, 0.036, 0.048 MIU/kg/hour) which were continued for the subsequent 9 to 21 hours. The principal end point was the status of the infarct-related coronary artery 12 to 24 hours after the start of therapy, and before termination of rt-PA, in patients with initially patent vessels at 90 minutes. Of the 103 responders with repeat angiograms after a 9 to 21 hour maintenance infusion of rt-PA, a total of 17 (16.5%) patients reoccluded across all doses administered. There was no significant relationship between the maintenance dose rate and the incidence of reocclusion. However, there was strong association between total dose of rt-PA administered and the incidence (16%) of serious or life-threatening bleeding exclusive of surgery. Other factors associated with serious bleeding included low body weight, female gender, and total duration of rt-PA infusion. Reocclusion was independent of the 90-minute Thrombolysis in Myocardial Infarction trial perfusion grade and diameter of infarct vessel. Rethrombosis after establishment of early patency after rt-PA remains a significant problem that is unaffected by sustained rt-PA infusion in doses that can be tolerated.

Vampire bat salivary plasminogen activator promotes rapid and sustained reperfusion without concomitant systemic plasminogen activation in a canine model of arterial thrombosis

The efficacy of recombinant vampire bat salivary plasminogen activator (bat-PA) as a thrombolytic agent was compared with that of human tissue-type plasminogen activator (t-PA) in a canine model of arterial thrombosis. An occlusive thrombus was formed in the femoral artery by insertion of a thrombogenic copper coil; femoral arterial blood flow was monitored with a Doppler flow meter. Bat-PA and t-PA, when administered by 5-minute intravenous infusion (14 nmol/kg), reperfused seven out of eight and four out of eight dogs, respectively. The median reperfusion times in the bat-PA and t-PA groups were 24 and greater than or equal to 131 minutes, respectively. The mean reperfusion times (+/- SEM) in the recanalized bat-PA- and t-PA-treated dogs were similar (20 +/- 5 and 11 +/- 2 minutes, respectively, p = NS). Maximal blood flow after reperfusion was greater with bat-PA than with t-PA (80 +/- 10% and 41 +/- 15% of control flow, respectively, p less than 0.05). Furthermore, the median reocclusion time was markedly delayed in the bat-PA group relative to the t-PA group (131 versus 34 minutes, respectively, p less than 0.05). Plasma fibrinogen and plasminogen were not significantly depleted by the administration of t-PA or bat-PA. However, plasma alpha 2-antiplasmin activity was moderately depressed in the t-PA group relative to the bat-PA group (p less than 0.05). The clearance profile for t-PA was monoexponential, with a half-life (t1/2) of 2.4 +/- 0.3 minutes and a mean residence time of 3.5 +/- 0.4 minutes. The clearance profile for bat-PA was biexponential, with a t1/2 alpha of 0.9 +/- 0.2 minutes, a t1/2 beta of 20.2 +/- 2.7 minutes, and a mean residence time of 21.3 +/- 4.3 minutes. The steady-state volume of distribution displayed by bat-PA was 16-fold greater than that of t-PA. Zymography of serial plasma samples from the bat-PA-treated dogs failed to demonstrate the apparent generation of a complex between bat-PA and plasminogen activator inhibitor-1; the corresponding complex with t-PA was observed in plasma samples from the t-PA-treated dogs. The sustained recanalization and improved blood flow in the bat-PA group relative to the t-PA group and the avoidance of fibrinogenolysis by bat-PA, despite its prolonged mean residence time, suggest that bat-PA may be superior to t-PA as a thrombolytic agent.

Effects of aspirin on coronary reocclusion and recurrent ischemia after thrombolysis: a meta-analysis

Reocclusion of infarct-related coronary arteries within 2 weeks of thrombolytic therapy varies from 5% to 45% and neither clinical nor angiographic variables have been proved to be predictive of reocclusion. The goal of the present study was to evaluate whether aspirin could prevent coronary reocclusion and recurrent ischemia after thrombolysis. For this purpose, a meta-analysis including 32 studies was performed. Although the studies showed very similar demographic data, the reocclusion rate assessed by angiography in 419 patients treated with aspirin was 11% compared with 25% in 513 patients without aspirin therapy (p less than 0.001). Recurrent ischemic events were present in 25% of 2,977 patients treated with aspirin and 41% of 721 patients treated without aspirin (p less than 0.001). The effect of aspirin was similar in trials with either streptokinase or recombinant tissue-type plasminogen activator (rt-PA). Thus, aspirin in the presence of heparin might prevent coronary reocclusion after thrombolysis.

Accelerated plasminogen activator dose regimens for coronary thrombolysis. The TAMI-7 Study Group

To determine the clinical profile and efficacy of accelerated recombinant tissue-type plasminogen activator (rt-PA) dose regimens, five different strategies of thrombolytic therapy in a total of 232 patients were systematically evaluated in the setting of acute myocardial infarction. The fifth strategy involved a combination of accelerated rt-PA and intravenous urokinase (regimen E). A weight-adjusted dose of 1.25 mg/kg body weight of tissue plasminogen activator over 90 min (regimen C) yielded the highest coronary patency rate (83%) at acute angiography. The associated in-hospital reocclusion rate for this regimen was low (4%). An exaggerated (60-min) dosage regimen yielded an inferior coronary patency rate (63%). Combination therapy (regimen E) was associated with a 72% patency rate and 3% reocclusion rate. Marginal improvement in global ejection fraction and regional wall function was demonstrated with all strategies by predischarge catheterization. Bleeding complications were most common at the periaccess site and were not different from those in previous experiences reported with conventional 3-h dosing regimens. Measurements of baseline, 30-min and 3-h levels of tissue plasminogen activator, fibrinogen and fibrin(ogen) degradation products were obtained. At 3 h, fibrinogen levels of less than 1 g/liter were demonstrated with combination therapy (regimen E) as well as with regimen C. Major clinical outcomes including death, reocclusion and reinfarction also showed a tendency to be less common with regimen C. Therefore, although accelerated dose regimens of rt-PA do not reliably yield acute coronary patency rates greater than 85%, an acute coronary patency rate of approximately 85% can be approached.(ABSTRACT TRUNCATED AT 250 WORDS)

New developments in thrombolytic therapy

Pharmacologic lysis of occlusive, ischemia-producing thrombi has become widely accepted during the past decade. New developments in this field have centered around increasing the efficacy of the known plasminogen activators while employing methods to minimize the risk of hemorrhage and decrease the incidence of rethrombosis. Such methods have included the use of thrombus-directed antibodies linked to plasminogen activators, increased plasminogen (substrate) concentration at the thrombus site, anticoagulant and antiplatelet therapy to prevent thrombus propagation and reformation following lysis, and combination plasminogen activator therapy designed to increase efficacy and safety. These new strategies have been extensively tested in vitro and in a variety of animal models. As we have indicated, extrapolation of such results to human patients cannot be done with confidence. However, the strategies are based on sound rationale and the reported findings should serve as the basis for controlled human trials.

Residual coronary stenoses and calculated transstenotic gradients after intravenous streptokinase versus tissue plasminogen activator

To compare the relative success of intravenous streptokinase (STK) and tissue plasminogen activator (TPA) on the severity of residual infarct-related coronary stenoses, we evaluated 45 patients receiving thrombolytic therapy for acute myocardial infarction. Twenty-three patients (18 men and 5 women) received STK (1.5 million units), while 22 patients (18 men and 4 women) received TPA (100 mg) within 6 hours of chest discomfort. Cardiac catheterization was performed before hospital discharge (8 days) with quantitative coronary arteriography and estimation of transstenotic pressure gradients using fluid dynamic equations. Although angina pectoris was equally common (STK, 7 of 23 [30%] versus TPA, 5 of 22 [23%], p = NS), recurrent infarction (STK, 3 of 23 [13%] versus TPA, 7 of 22 [32%], p less than 0.05) and coronary angioplasty (STK, 2 of 23 [9%] versus TPA, 7 of 22 [32%], p less than 0.05) were more frequent in those receiving TPA. Infarct-related coronary patency was greater in TPA-treated subjects (STK, 15 of 23 [65%] versus TPA, 19 of 22 [86%], p less than 0.05), although minimum stenotic diameter (STK, 0.77 +/- 0.48 mm versus TPA, 0.57 +/- 0.38 mm, p less than 0.05), and calculated transstenotic pressure gradient (STK, 8.7 +/- 17.0 mm Hg versus TPA, 23.7 +/- 30.2 mm Hg, p less than 0.05) suggested severe residual stenosis. These effects were accentuated at elevated coronary flow velocities (8 to 20 cm/sec).(ABSTRACT TRUNCATED AT 250 WORDS)

Experience with low-dose intracoronary recombinant tissue-type plasminogen activator for nonacute total occlusions before percutaneous transluminal coronary angioplasty

The primary success rate for angioplasty of total occlusions is significantly worse than for subtotal lesions. Pharmacologic recanalization of total occlusions before angioplasty has the potential to improve the primary success rate. To determine the ability of recombinant tissue-type plasminogen activator (rt-PA) to recanalize occlusive thrombi before elective percutaneous transluminal coronary angioplasty, 12 patients with total occlusions, 100% obstruction and Thrombolysis in Myocardial Infarction (TIMI) grade 0 flow, and 5 with functional total occlusions, severe stenoses and TIMI grade 1 flow received an intracoronary infusion of rt-PA. The first 10 patients received 0.2 mg/min for 90 minutes, and the next 7 patients received 0.4 mg/min for 60 minutes. Flow improved by greater than or equal to 1 TIMI grade in 11 patients. Mean TIMI flow improved from 0.3 +/- 0.5 to 1.5 +/- 1.2 (p less than 0.0001). There was a significant improvement in severity of stenosis after rt-PA infusion by both digital caliper (99 +/- 2 vs 84 +/- 16%; p less than 0.0001) and quantitative videodensitometric area assessment (99 +/- 3 vs 94 +/- 6%; p less than 0.004). Angioplasty was successful in 16 of 17 patients (94%). There were 2 out-of-laboratory abrupt closures at 4 days; both were medically treated and 1 had a small myocardial infarction. Only 1 patient had a bleeding complication significant enough to need a transfusion. It is concluded that low-dose intracoronary rt-PA is effective at lysing thrombi less than 3 weeks old. This approach warrants further investigation since it may significantly improve the primary success rate of percutaneous transluminal coronary angioplasty in patients with occlusive thrombus.

Thrombolysis, anticoagulation, and reocclusion

Based on apparent higher recanalization rates of the infarct-related artery, preferential use of thrombolytic agents with high clot specificity has been proposed for treating patients with acute myocardial infarction. In the Thrombolysis in Myocardial infarction (TIMI-I) and European Cooperative Group studies, higher reperfusion rates were observed with alteplase compared with streptokinase, causing many to assume that the former would achieve a greater reduction in early hospital mortality. However, the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI-2) and its associated International Study Group failed to show any differences in 15-day mortality between these agents in more than 20,000 patients. This apparent lack of correlation between reperfusion rates and early mortality may be explained in part when one considers that recanalization or patency rates measured at a given point in time, such as 90 minutes after onset of therapy, fail to define the subsequent vessel status. Early reocclusion is the major reason for this and is a major limitation to the clinical efficacy of thrombolytic drugs. Following recanalization, residual fibrin-bound thrombin adherent to the site of arterial injury from plaque rupture strongly promotes rethrombosis. Although antiplatelet and antithrombin agents such as aspirin and heparin help to decrease rethrombosis, these agents are far from ideal. Thrombolytic agents that produce a significantly prolonged systemic thrombolytic state, such as streptokinase and anistreplase, are likely to result in less rethrombosis. Therefore, a systemic fibrinolytic state would appear to be an advantage rather than a disadvantage, particularly because the incidence of intracerebral hemorrhage does not appear to be greater with their use compared with agents producing less systemic fibrinolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Creation of the recombinant tissue plasminogen activator (rt-PA) image and its influence on practice habits

American physicians have commonly practiced thrombolytic therapy for acute myocardial infarction with the recombinant form of tissue plasminogen activator (rt-PA), although its cost is much higher than that of streptokinase. The greater popularity of rt-PA is based on the belief that it is a more effective and a safer drug for achieving myocardial salvage and mortality reduction. However, a series of studies testing this assumption have not substantiated its greater efficacy or safety with respect to not only streptokinase but also urokinase and anisoylated plasminogen-streptokinase activator complex (APSAC). This editorial reviews the sequence of events that led to the creation of the rt-PA image, the mistaken premises on which it was based and the questions that need to be addressed if we are to strengthen the scientific method for evaluating similar types of drugs and its influence on practice habits including the costs to the health system.

Prevention of arterial reocclusion after thrombolysis with recombinant lipoprotein-associated coagulation inhibitor

BACKGROUND

This study was designed to determine whether arterial reocclusion after thrombolysis can be prevented by lipoprotein-associated coagulation inhibitor (LACI), a physiological inhibitor of tissue factor-induced coagulation mediated by the extrinsic pathway.

METHODS AND RESULTS

Thrombosis was induced in femoral arteries of anesthetized dogs with the use of anodal current to elicit extensive vascular injury and formation of platelet-rich thrombi in one artery and with thrombogenic copper wire to elicit fibrin-rich thrombi without appreciable vascular injury in the contralateral artery. Recanalization of both vessels was induced with t-PA (1.7 mg/kg i.v. over 1 hour) and verified with Doppler flow probes. Reocclusion occurred within 2 hours in seven of seven arteries with electrical injury-induced thrombosis and in four of seven arteries with copper wire-induced thrombosis in the absence of LACI. In dogs given infusions of recombinant DNA-produced LACI (225 micrograms/kg over 15 minutes, followed by 4 micrograms/kg/min i.v.) after completion of the infusion of t-PA, no reocclusion occurred during the 2-hour interval of observation in any of the five arteries subjected to electrical injury (p less than 0.001), and cyclic partial occlusions were nearly abolished (0.4 +/- 0.4/hr in LACI-treated dogs compared with 13.7 +/- 5.5/hr in saline-treated dogs, p less than 0.0001). In contrast, reocclusion occurred in two of five arteries with indwelling copper wires, and cyclic partial occlusions were unaffected despite LACI. LACI prolonged the partial thromboplastin time modestly (1.7 +/- 0.2 x baseline) but did not affect platelet counts or aggregation assessed ex vivo.

CONCLUSIONS

Inhibition of the extrinsic pathway of coagulation with LACI prevents thrombotic arterial reocclusion after thrombolysis in vessels subjected to extensive vascular injury. Our results demonstrate that activation of the extrinsic pathway plays a critical role in thrombotic reocclusion and that LACI provides a highly targeted approach to facilitate sustained recanalization without directly inhibiting platelets.

A prospective, randomized trial comparing combination half-dose tissue-type plasminogen activator and streptokinase with full-dose tissue-type plasminogen activator. Kentucky Acute Myocardial Infarction Trial (KAMIT) Group

BACKGROUND

The potential benefits of combination thrombolytic agents in the treatment of myocardial infarction remain uncertain. In a small pilot study, we demonstrated that combining half-dose tissue-type plasminogen activator (t-PA) with streptokinase (SK) achieved a high rate of infarct vessel patency and a low rate of reocclusion at half the cost of full-dose t-PA.

METHODS AND RESULTS

We designed a prospective trial in which 216 patients were randomized within 6 hours of myocardial infarction to receive either the combination of half-dose (50 mg) t-PA with streptokinase (1.5 MU) during 1 hour or to the conventional dose of t-PA (100 mg) during 3 hours. Acute patency was determined by angiography at 90 minutes, and angioplasty was reserved for failed thrombolysis. Heparin and aspirin regimens were maintained until follow-up catheterization at day 7. Acute patency was significantly greater after t-PA/SK (79%) than with t-PA alone (64%, p less than 0.05). After angioplasty for failed thrombolysis, acute patency increased to 96% in both groups. Marked depletion of serum fibrinogen levels occurred after t-PA/SK compared with t-PA alone at 4 hours (37 +/- 36 versus 199 +/- 66 mg/dl, p less than 0.0001) and persisted 24 hours after therapy (153 +/- 66 versus 252 +/- 75 mg/dl, p less than 0.0001). Reocclusion (3% versus 10%, p = 0.06), reinfarction (0% versus 4%, p less than 0.05), and need for emergency bypass surgery (1% versus 6%, p = 0.05) tended to be less in the t-PA/SK group. Greater myocardial salvage was apparent in the t-PA/SK group as assessed by infarct zone function at day 7 (-1.9 SD/chord versus -2.3 SD/chord after t-PA alone, p less than 0.05). In-hospital mortality (6% versus 4%) and serious bleeding (12% versus 11%) were similar between the two groups.

CONCLUSIONS

These results suggest that a less expensive regimen of half-dose t-PA with SK yields superior 90-minute patency and left ventricular function and a trend toward reduced reocclusion compared with the conventional dose of t-PA.

Improved coronary thrombolysis by tissue-type plasminogen activator in the presence of BAY U 3405

The effect of BAY U 3405 (3 mg/kg i.v.) was tested on recombinant tissue-type plasminogen activator (rt-PA)-induced thrombolysis of an experimentally induced coronary thrombosis in anaesthetized dogs. BAY U 3405, given immediately before an rt-PA infusion, reduced time to reperfusion by more than 50% compared with vehicle-treated controls (P less than 0.01). After cessation of the rt-PA infusion, BAY U 3405 reduced the reocclusion rate compared to controls (P less than 0.05). These results show that BAY U 3405 improves rt-PA-induced coronary thrombolysis in a canine model.

Evaluation of combination thrombolytic therapy and timing of cardiac catheterization in acute myocardial infarction. Results of thrombolysis and angioplasty in myocardial infarction--phase 5 randomized trial. TAMI Study Group

Recent trials of myocardial reperfusion using single-agent thrombolytic therapy and sequential cardiac catheterization have supported a conservative approach to the patient with acute myocardial infarction. To evaluate combination thrombolytic therapy and the role of a previously untested strategy for the aggressive use of cardiac catheterization, we performed a multicenter clinical trial with a 3 x 2 factorial design in which 575 patients were randomly allocated to one of three drug regimens--tissue-type plasminogen activator (t-PA) (n = 191), urokinase (n = 190), or both (n = 194) - and one of two catheterization strategies--immediate catheterization with angioplasty for failed thrombolysis (n = 287) or deferred predischarge catheterization on days 5-10 (n = 288). Patients with contraindications to thrombolytic therapy, cardiogenic shock, or age of more than 75 years were excluded. Global left ventricular ejection fraction was well preserved and almost identical at predischarge catheterization (54%), regardless of the catheterization or thrombolytic strategy used (p = 0.98). Combination thrombolytic therapy was associated with a less complicated clinical course, most clearly documented by a lower rate of reocclusion (2%) compared with urokinase (7%) and t-PA (12%) (p = 0.04) and a lower rate of recurrent ischemia (25%) compared with urokinase (35%) and t-PA (31%). When a composite clinical end point (e.g., death, stroke, reinfarction, reocclusion, heart failure, or recurrent ischemia) was examined, combination thrombolytic therapy was associated with greater freedom from any adverse event (68%) compared with either single agent (urokinase, 55%; t-PA, 60%) (p = 0.04) and with a less complicated clinical course when the composite clinical end points were ranked according to clinical severity (p = 0.024). Early patency rates were greater with combination therapy, although predischarge patency rates after considering interventions to maintain patency were similar among drug regimens. No difference in bleeding complication rates was observed with any thrombolytic regimen. The aggressive catheterization strategy led to an overall early patency rate of 96% and a predischarge patency rate of 94% compared with a 90% predischarge patency in the conservative strategy (p = 0.065). The aggressive strategy improved regional wall motion in the infarct region (-2.16 SDs/chord) compared with deferred catheterization (-2.49 SDs/chord) (p = 0.004). More patients treated with the aggressive strategy were free from adverse outcomes (67% versus 55% in the conservative strategy, p = 0.004), and the clinical course was less complicated when the adverse outcomes were ranked according to severity (p = 0.016). No significant increase in use of blood products resulted from the aggressive strategy.(ABSTRACT TRUNCATED AT 400 WORDS)