Thrombolysis with recombinant tissue plasminogen activator in atherosclerotic thrombotic occlusion

Calculation of Coronary Angiographic Total Blush in Patients with Coronary Artery Disease and its Prognostic Implication

BACKGROUND

Myocardial perfusion grade (MPG) is an accepted method of evaluating myocardial perfusion. However, it does not take into the account, the extent of the perfusion. We hypothesized that myocardial blush area times MPG (total blush) would be more accurate than simple MPG, and yield better prognostic information.

METHODS

About 34 patients were recruited after they had consented to both coronary angiography (CAG) and single photon emission computed tomography (SPECT), and divided into two groups. A special dedicated computer was employed to calculate the total blush. The CAG was performed as a conventional way. Scintigraphic technetium 99m methoxyisobutyl-isonitrile rest and stress images were evaluated quantitatively. The comparison was made between stenosis versus chronic total occlusion (CTO), MPG 1, 2 versus MPG 3, percutaneous intervention (PCI) successful versus failure. A correlation was made between ejection fraction (EF) and myocardial perfusion by MPG, total blush, SPECT, and syntax score.

RESULTS

The perfusion indices of total blush, summed difference score (SDS) and syntax score were insignificant between the two groups (P > 0.05). However, the left ventricular end diastolic volume was significantly larger in CTO (P < 0.05). The patients with stenosis had better MPG than with CTO (P < 0.05). The increased MPG was associated with increased total blush, higher syntax score, and EF (P < 0.05). Successful PCI resulted in better perfusion indicated by increased total blush, and MPG (P < 0.05) but successful PCI did not change syntax score, EF and SDS significantly. Multivariate linear analysis with EF as the dependent factor and syntax score, SDS, total blush, blush area, and MPG as the independent factors showed a significantly higher degree of correlation (R = 0.87, P < 0.05).

CONCLUSION

After PCI the total blush and EF improved significantly indicating its potential application in the future.

Characterization of a tissue factor/factor VIIa-dependent model of thrombosis in hypercholesterolemic rabbits

Tissue factor (TF) expressed in arterial atherosclerotic plaque plays a key role in activating the extrinsic coagulation pathway and triggering acute coronary syndromes. In this study, we developed and characterized a TF-factor (F)VIIa-mediated thrombosis model in rabbits. Balloon catheter-induced endothelial denudation in the femoral artery and a 4-week high cholesterol diet produced a localized atherosclerotic plaque at the injured site. High levels of TF mRNA and TF protein antigen (152 +/- 25 vs. 49 +/- 12 pg mg-1 protein in normal vessels) were detected in these atherosclerotic plaques. Plasma FVII coagulant activity (FVII:C) was significantly increased in the hypercholesterolemic rabbits (36 +/- 1 s) compared with the normal rabbits (44 +/- 1 s, P < 0.0001). Plaque rupture was induced by balloon angioplasty, which resulted in thrombus formation in the injured vessel segment after a brief period of stasis. FVIIai, a specific TF-FVIIa inhibitor, was administered intravenously to rabbits before plaque rupture at 0.3 and 1.0 mg kg-1. FVIIai dose-dependently reduced thrombus mass (14.7 +/- 2.5 and 5.9 +/- 2.2 mg, respectively, vs. 21.6 +/- 1.9 mg in the control group). PD198961, a novel factor Xa inhibitor, and argatroban, a thrombin inhibitor, also dose-dependently inhibited thrombosis. These results indicate that thrombus formation in this model is initiated by the activation of TF-FVIIa pathway, which is attributed to TF expression in the atherosclerotic plaque and enhanced plasma FVII coagulant activity. This model may be useful for evaluating in vivo efficacy of new antithrombotic drugs, particularly TF-FVIIa inhibitors.

Pharmacologic reperfusion therapy for acute myocardial infarction

Acute myocardial infarction (MI) remains a significant problem in terms of morbidity, mortality and healthcare costs. Pharmacologic reperfusion therapies for MI are becoming increasingly complex. This review therefore places contemporary pharmacologic MI developments into perspective. An historical overview of pharmacologic reperfusion therapy for MI is provided, followed by an analysis of current limitations, treatment options, and present and likely future pharmacologic therapies. Adjunctive percutaneous and other treatments are also discussed, to clarify what is becoming a rapidly changing field.

Angiographic study of mutant tissue-type plasminogen activator versus urokinase for acute myocardial infarction

The effects and problems of intravenous thrombolytic therapy with a bolus injection of mutant tissue plasminogen activator (t-PA) were investigated in 34 patients with first acute myocardial infarction (AMI). In contrast, 114 patients were selected from 1,003 patients with AMI for treatment using intravenous infusion urokinase (UK). Angiography of these 148 patients revealed a complete occlusion of infarct-related artery with no clear contraindications to the study treatment. With the exception of thrombolysis in myocardial infarction (TIMI-3) recanalization 60 min after a bolus injection of mutant t-PA, the patients were given intracoronary UK in addition to mutant t-PA. The study comparisons were assessed using the following criteria: (1) 60-min assessment of recanalization rates, mutant t-PA vs UK; (2) time interval from initiation of thrombolysis to recanalization, mutant t-PA vs UK; (3) angiographic reocclusion rates within 1 month, mutant t-PA alone vs UK vs mutant t-PA plus UK; and (4) intracerebral hemorrhage rates, mutant t-PA alone vs UK vs mutant t-PA plus UK. There were no significant differences in the recanalization rates between mutant t-PA and UK, but there was a significant reduction in the time to recanalization with mutant t-PA (31.8 +/- 12.7 min) compared with UK (56.5 +/- 6.3 min). There was a significant difference in the reocclusion rates among the 3 treatment groups (20% mutant t-PA alone vs 4% UK vs 0% mutant t-PA plus UK). On the other hand, no significant differences in intracerebral hemorrhage rates among the 3 treatments were observed. In conclusion, thrombolytic therapy with a bolus injection of mutant t-PA achieved more rapid recanalization, but treatment with mutant t-PA led to a high rate of reocclusion.

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)

Comparison of two dose regimens of intravenous tissue plasminogen activator for acute myocardial infarction

Two dosing schedules of intravenous tissue plasminogen activator (t-PA) for acute myocardial infarction were compared in a multicenter trial. At 2.95 +/- 1.1 hours from onset of chest pain, 386 patients received 150 mg of intravenous t-PA. For the first 178 patients (group A), 60 mg were given in the first-hour dose and the remaining 90 mg were infused over 7 hours. In the subsequent 208 patients (group B), the first-hour dose was 1.0 mg/kg and the remaining 150 mg were given over 5 hours. At initial angiography 94 +/- 30 minutes into therapy, the infarct vessel patency was 64% in group A versus 75% in group B (p = 0.02). By final angiography with up to 4 selective contrast injections, patency was 68% versus 77%, respectively (p = 0.06). Repeat angiography at 7 to 10 days demonstrated reocclusion in 17% of group A and 13% of group B patients (p = 0.35). There was no difference in fibrinogen nadir or mean hematocrit drop between the 2 groups: 120 mg/dl and 11 points, respectively, in group A compared with 120 mg/dl and 10 points in group B. However, bleeding was reduced in group B patients as evident by a decrease in requirement for greater than or equal to 2 units of packed red blood cell transfusion (group A 36%, group B 27%, p = 0.05) and lower incidence of gastrointestinal bleeding (group A 12%, group B 4%, p = 0.002). To further study the importance of weight adjustment, patients were divided into 2 groups according to weight (less than or equal to 90 kg versus greater than 90 kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombolytic therapy for patients with acute myocardial infarction

Thrombolytic therapy is becoming an important addition to the care of patients with transmural (Q-wave) myocardial infarction. In this review, the authors analyze the mechanisms of effect and thrombolytic capabilities of several currently used thrombolytic interventions and review the influence of reperfusion in reducing mortality and protecting segmental ventricular function in animal models and patients. The problems related to thrombolytic therapy also are discussed and patient subgroups most likely to benefit from thrombolytic therapy identified. Finally, the authors speculate concerning future alterations in thrombolytic agents and additions to thrombolytic therapy as they might be usefully applied in the care of patients with acute transmural myocardial infarcts.

Beneficial effects of tissue-type plasminogen activator in acute myocardial ischemia in cats

Tissue-type plasminogen activator is a new thrombolytic agent that dissolves intravascular thrombi in coronary and peripheral vessels with less pronounced systemic lysis than that produced by streptokinase. Plasminogen activator was shown to induce reperfusion, and to salvage ischemic myocardium, by lysing experimentally induced coronary artery thrombi. The effect of a melanoma cell-derived tissue-type plasminogen activator was studied in cat myocardium rendered ischemic by coronary artery ligation for 2 hours and reperfused for another 4 hours. Plasminogen activator was infused at a rate of 500 IU X kg-1 X min-1 for the first 30 minutes of reperfusion. The marked increase in plasma creatine kinase activity during reperfusion was significantly lower in plasminogen activator-treated cats at 4, 5 and 6 hours, with 7.7 +/- 1.5 X 10(-3) IU X mg protein-1 (n = 8) in the plasminogen activator group versus 17.8 +/- 3.5 X 10(-3) IU X mg protein-1 (n = 7) in the vehicle group at 6 hours (mean +/- SEM). The area at risk in the two ischemic groups was not different, being 14.6 +/- 1.5 and 16.6 +/- 1.4% of total left ventricular mass for the treated and untreated groups, respectively. However, the mass of necrotic tissue determined histochemically was significantly lower in the plasminogen activator-treated group, accounting for 29.5 +/- 3.9% of the area at risk compared with 46.8 +/- 4.2% of area at risk in cats receiving only the vehicle (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Regional wall motion improvement after coronary thrombolysis with recombinant tissue plasminogen activator: importance of coronary angioplasty

To evaluate functional recovery in 20 consecutive patients with acute myocardial infarction who received recombinant tissue-type plasminogen activator, serial two-dimensional echocardiograms were performed before and immediately after tissue plasminogen activator administration and at 1 and 10 days postinfarction. Tissue plasminogen activator was administered intravenously (17 patients) or by intracoronary infusion (3 patients) after angiographic confirmation of total occlusion. Reperfusion, documented by angiography, occurred in 13 of the 20 patients. The mean time from onset of chest pain to thrombolysis was 5.1 +/- 1.1 hours. Echocardiograms were evaluated for regional function with a visual semiquantitative scoring system by two independent observers who had no knowledge of patient identity, temporal sequence, therapy or effect of therapy. There was no immediate or 24 hour improvement in wall motion. At day 10 compared with pretreatment, 28 of 33 reperfused infarct zone segments versus 6 of 20 nonreperfused infarct segments demonstrated improved wall motion (p = 0.01). This improvement did not relate to time from onset of chest pain to successful thrombolysis. Of reperfused infarct zone segments in the distribution of coronary artery balloon dilation, 19 of 23 segments exhibited improvement versus 7 of 17 (reperfused, no angioplasty) and 6 of 20 (nonreperfused, no angioplasty) segments (p = 0.001). Infarct zone segments reperfused at the time of ongoing chest pain demonstrated functional recovery compared with segments reperfused in the absence of chest pain (18 of 23 versus 10 of 20, respectively; p = 0.05). Thus, in this uncontrolled series, there was echocardiographically detectable improvement in function of reperfused infarct segments 10 days after coronary thrombolysis with recombinant tissue plasminogen activator.

Applicability of percutaneous transluminal coronary angioplasty to patients with recombinant tissue plasminogen activator mediated thrombolysis

To test the utility and safety of percutaneous transluminal coronary angioplasty (PTCA) after recombinant tissue plasminogen activator (t-PA), we performed the procedure in all suitable candidates with acute myocardial infarction (MI) who had successful t-PA mediated coronary thrombolysis. Twenty consecutive patients with MI received t-PA after coronary angiographic conformation of total occlusion. Successful recanalization with t-PA was achieved in 13 patients, leaving a residual obstruction of 84 +/- 6% in the nine patients for whom PTCA was attempted at a mean of 21.6 h. Success was achieved in seven patients, leading to a residual lesion of 29 +/- 7%. In the two patients for whom PTCA was unsuccessful, total reocclusion occurred prior to the attempt despite therapy with heparin, aspirin, dipyridamole, and nifedipine. All PTCA procedures were uncomplicated. Serial two-dimensional echocardiography at 10 days, compared to admission, demonstrated infarct zone wall motion index improvement in the patients with successful PTCA (group A, 0.83 +/- 0.36 to 1.46 +/- 0.49) as compared to the 13 patients without thrombolysis or successful PTCA (group B, 0.61 +/- 0.26 to 0.66 +/- 0.39), (P less than 0.05). One patient of group A sustained a massive stroke at 2 weeks after hospital discharge. In the remaining six patients, follow-up exercise testing and/or coronary arteriography demonstrated a negative treadmill test and/or patent infarct vessel, respectively. After successful PTCA, no patient had clinical signs of reocclusion, reinfarction, postinfarction angina, or congestive heart failure. At 9.4 +/- 2 months, all six patients are asymptomatic and have returned to work. Thus, sequential PTCA after t-PA can be performed safely and successfully in patients with MI and this approach may be associated with improved regional function and a favorable post-MI course.