Intracoronary fibrinolytic therapy in acute myocardial infarction. Report of a prospective randomized trial

Analytic Review: Thrombolytic Therapy in Acute Myocardial Infarction

The salvage of myocardium in the setting of acute myocardial infarction has long been a goal of physicians involved in the care of patients with coronary artery disease. Understanding the role of thrombosis in the pathogenesis of acute myocardial infarction has led the way to an entirely new approach to the treatment of this entity. Thrombolytic therapy has now become a widely used form of treatment with encouraging results. Both intravenous and intracoronary administration of thrombolytic agents have been shown to promote recanalization of acutely occluded coronary arteries. Results of studies using the clot-specific agent, tissue plasminogen activator, intravenously have been most encouraging; successful reperfusion has been obtained in approximately 70% of patients treated. In addition, a recent large-scale trial has shown a reduction in morbidity and mortality with the early use of thrombolytic agents.

Ongoing trials should help delineate the precise role and timing of these agents as the initial form of therapy for acute myocardial infarction. Other issues that remain unresolved are the frequency of restenosis and the role of percutaneous transluminal coronary angioplasty in addition to thrombolytic therapy in the treatment of acute myocardial infarction.

Reperfusion therapy for acute myocardial infarction: Concepts and controversies from inception to acceptance

More than 20 years of misconceptions derailed acceptance of reperfusion therapy for acute myocardial infarction (AMI). Cardiologists abandoned reperfusion for AMI using fibrinolytic therapy, explored in 1958, because they no longer attributed myocardial infarction to coronary thrombosis. Emergent aortocoronary bypass surgery, pioneered in 1968, remained controversial because of the misconception that hemorrhage into reperfused myocardium would result in infarct extension. Attempts to limit infarct size by pharmacotherapy without reperfusion dominated research in the 1970s. Myocardial necrosis was assumed to progress slowly, in a lateral direction. At least 18 hours was believed to be available for myocardial salvage. Afterload reduction and improvement of the microcirculation, but not reperfusion, were thought to provide the benefit of streptokinase therapy. Finally, coronary vasospasm was hypothesized to be the central mechanism in the pathogenesis of AMI. These misconceptions unraveled in the late 1970s. Myocardial necrosis was shown to progress in a transmural direction, as a "wave front," beginning with the subendocardium. Reperfusion within 6 hours salvaged a subepicardial ischemic zone in experimental animals. Acute angiography provided in vivo evidence of the high incidence of total coronary occlusion in the first hours of AMI. In 1978, early reperfusion by transluminal recanalization was shown to be feasible. The pathogenetic role of coronary thrombosis was definitively established in 1979 by demonstrating that intracoronary streptokinase rapidly restored flow in occluded infarct-related arteries, in contrast to intracoronary nitroglycerine which rarely did. The modern reperfusion era had dawned.

Evolution of Reperfusion Therapies for Acute Brain and Acute Myocardial Ischemia

Background and Purpose—

Early reperfusion is the most effective therapy for both acute brain and cardiac ischemia. However, the cervicocephalic circulatory bed offers more challenges to recanalization interventions. The historical development of reperfusion interventions has not previously been systematically compared.

Methods—

Medline search identified all multi-arm, controlled trials of coronary revascularization for acute myocardial infarction and multicenter trials of cerebral revascularization for acute ischemic stroke reporting angiographic reperfusion rates.

Results—

Thirty-seven trials of coronary reperfusion enrolled 10 908 patients from 1983 to 2009, and 10 trials of cerebral reperfusion enrolled 1064 patients from 1992 to 2009. Coronary reperfusion trials included 10 of intravenous fibrinolysis alone, 8 combined intravenous fibrinolysis and percutaneous transluminal coronary angioplasty with or without stenting, 3 intra-arterial fibrinolysis, and 16 percutaneous transluminal coronary angioplasty with or without stenting. Cerebral reperfusion trials included 1 of intravenous fibrinolysis alone, 3 intra-arterial fibrinolysis, 3 endovascular device alone, and 3 of endovascular treatment ± intravenous fibrinolysis. In both circulatory beds, endovascular treatments were more efficacious at achieving reperfusion than peripherally administered fibrinolytics. In the coronary bed, rates of achieved reperfusion began at high levels in the 1980s and improved modestly over the subsequent 3 decades. In the cerebral bed, reperfusion rates began at modest levels in the early 1990s and increased more slowly. Most recently, in 2005 to 2009, cardiac reperfusion rates substantially exceeded cerebral, partial reperfusion 86.1% versus 61.1%, complete reperfusion 78.6% versus 23.4%.

Conclusions—

Reperfusion therapies developed more slowly and remain less effective for cerebral than cardiac ischemia. Further, cerebral circulation–specific technical advances are required for physicians to become as capable at safely restoring blood flow to the ischemic brain as the ischemic heart.

Effect of very early intravenous streptokinase infusion in patients with evolving myocardial infarction

The effect of very early infusion of 1.5 X 10(6) U of streptokinase intravenously was studied in 29 patients with nitroglycerin-resistant chest pain and ST-segment elevation. Infarct size was estimated from maximal LD1 isoenzyme levels, and the diagnosis confirmed by CK-MB determination. Thrombolytic therapy was started within 1 hour of pain onset in 11 patients (group A), between 1 and 2 hours in 10 (group B), and later than 2 hours in eight patients (group C). Marked differences appeared between the groups. Thus, three patients in group A and one patient in group B did not develop infarction, all had critical LAD stenoses. Three patients in group C died in shock without bleeding. Further, the average maximal LD1 values in the 22 patients who survived their infarction differed significantly between the groups, and were 12.6, 19.1 and 36.2 mu kat/l in groups A, B and C, respectively. In conclusion, very early intravenous streptokinase infusion probably reduces myocardial necrosis, and possible prevents infarction in some patients.

Combined revascularization strategy for acute myocardial infarction in patients with intracoronary thrombus: preceding intracoronary thrombolysis and subsequent mechanical angioplasty

Thrombus in the infarct-related artery is one of the limitations for flow restoration in primary percutaneous transluminal coronary angioplasty (PTCA) treatment for acute myocardial infarction (AMI). The present study investigated the benefit of preceding intracoronary thrombolysis (ICT) by retrospectively analyzing acute phase flow restoration in 80 AMI patients with intracoronary thrombus: 40 undergoing primary PTCA alone (primary PTCA group) and 40 treated with preceding ICT plus PTCA (combined group). Acute phase Thrombolysis in Myocardial Infarction (TIMI) grade flow was as follows: TIMI 0/1: 35.0% vs 12.5% for the primary PTCA group and the combined group, p=0.06; TIMI 2: 7.5% vs 15.0%, p=NS; TIMI 3: 57.5% vs 72.5%, p=NS). In the subgroup analysis, it was also less in the combined group among 33 patients with a left anterior descending coronary artery (LAD) lesion (42.1 % vs 7.1%, p=0.08), but not among the remaining 47 with either a right coronary artery or left circumflex artery lesion. The combined therapy may potentially provide better acute phase flow restoration in AMI patients with an intracoronary thrombus in a LAD lesion.

Increased coronary vasomotor tone in acute myocardial infarction patients with spontaneous coronary recanalization

To clarify the role of coronary spasm or dynamic coronary obstruction in the development of acute myocardial infarction (AMI) with spontaneous recanalization (SR), symptoms in 296 patients with AMI admitted within 24 h after the onset of chest pain were analyzed just before and after onset, and coronary angiograms were analyzed soon after onset. Patients were divided into 3 groups according to the initial angiographic findings in the infarct-related coronary artery (IRCA): group 1 comprised 172 patients with total occlusion (TIMI O); group 2 comprised 57 patients with subtotal occlusion (TIMI 1,2); and group 3 comprised 67 patients with SR (TIMI 3). The incidence of SR was 20.3% at 0-4 h after onset, 22.2% at 4-6 h, 19.7% at 6-12 h, 24.0% at 12-24 h, and 36.0% at 24 h or later. The incidence of SR did not increase significantly as time elapsed. The incidence of angina at rest and variable-threshold angina before the onset of infarction was only 16.2% in group 1, but was significantly higher in groups 2 (64.3%) and 3 (61.9%). The incidence of intermittent chest pain at onset in group 1 (8.4%) was significantly lower than in groups 2 (54.5%) and 3 (38.8%). Vasodilation of the proximal normal segment adjacent to the stenotic site of the IRCA induced by intracoronary nitroglycerin was significantly higher in groups 2 (11.7 +/- 1.2%) and 3 (20.7 +/- 2.6%) than in group 1 (4.0 +/- 0.6%). These results suggest that coronary spasm or dynamic obstruction may be involved in the pathogenesis of thrombus formation or coronary obstruction causing AMI in many Japanese patients.

Reperfusion injury: a review of the pathophysiology, clinical manifestations and therapeutic options

Lack of blood supply or ischaemia underlies many of the most important cardiovascular and cerebrovascular diseases faced by clinicians in their daily practice. Many of these ischaemic episodes can be reversed at an early stage by surgical or pharmacological means with the ultimate aim of preventing infarction and cell necrosis in the ischaemic tissues. However, reperfusion of ischaemic areas, in particular the readmission of oxygen, may contribute to further tissue damage (reperfusion injury). For example, the use of thrombolytic therapy in acute myocardial infarction and other revascularisation procedures, such as percutaneous transluminal angioplasty and coronary artery bypass surgery, may be associated with reperfusion of ischaemic myocardium. Such ischaemia and reperfusion may result in injury to one of more of the biochemical, cellular and microvascular components of the heart. Our understanding of the significance of reperfusion injury is however restricted by the profuse literature in animal models and limited literature in the clinical situation. This article reviews the pathophysiology, clinical manifestations of reperfusion injury to the heart and discusses the possible therapeutic approaches to avoiding any adverse effects.

Thrombolytic therapy for cerebral infarction

Until recently, no clinically effective therapy for acute ischemic stroke has been available. Recent advances in the use of thrombolytic therapy for ischemic stroke appear promising in clinical care. As the use of thrombolytic therapy in acute stroke progress, emergency physicians (EPs) will become increasingly involved in its implementation. The EP must be cognizant of both prior and ongoing investigations in acute ischemic stroke therapy. To that end, this article reviews research in the field of thrombolytic therapy for acute ischemic stroke.

Comparison of "accelerated" tissue plasminogen activator with streptokinase for treatment of suspected myocardial infarction

PURPOSE

A computerized decision analysis, based on the results of published clinical trials, assessed the risks, benefits, and costs of different thrombolytic regimens for suspected myocardial infarction (MI) throughout the likely range of clinical circumstances.

DATA SOURCE

Medline search and articles' bibliographies.

STUDY SELECTION

All studies reporting efficacy and side effects of thrombolysis.

DATA ANALYSIS

Life-expectancy outcomes of thrombolytic therapies for possible MI modeled by decision analysis.

RESULTS

The analysis allows a clinician to estimate the benefits, risks, and relative costs of thrombolytic therapies throughout the likely range of individual clinical circumstances. When applied, for example, to the average patient in ISIS-2, estimated gains are 150 quality-adjusted days of life (QALDs) from treatment with streptokinase (SK) and 255 QALDs with "accelerated" tPA (tPA). tPA costs $1,686 more than SK, taking into account the cost of lifelong care of the extra strokes incurred. Nevertheless, the chances of stroke above which thrombolysis is not preferred are 5.0% for SK and 8.0% for tPA, with tPA remaining the preferred treatment for six hours after symptom onset; thereafter, SK is marginally preferred, but at much lower cost. Both regimens are beneficial in older patients provided the chances of MI and death are "average" or greater.

CONCLUSION

When the chances of MI and death are known, decision analysis can be a useful bedside tool to guide thrombolytic therapy and subsequently, if needed, to review and defend the treatment decisions made.

Clinical experience with intracoronary tissue plasminogen activator: results of a multicenter registry. Intracoronary t-PA Registry Investigators

Clinical experience with the use of intracoronary tissue plasminogen activator (t-PA) is limited. We therefore undertook this study to document current clinical usage of intracoronary t-PA during a 2-yr period in a multicenter registry. Intracoronary t-PA was utilized on 206 occasions in 198 patients (154 men and 44 women; mean age, 59 +/- 12 yr). The mean dose of intracoronary t-PA was 31 +/- 15 mg. Indications for use included acute myocardial infarction (MI) (n = 83), preexisting thrombus with (n = 49) or without (n = 41) percutaneous transluminal coronary angioplasty (PTCA), unstable angina (n = 14), abrupt vessel closure (n = 11), and post-PTCA "clean-up" (n = 8). The Thrombolysis in Myocardial Infarction (TIMI Phase I) criteria were used to assess perfusion and degree of thrombus formation. Overall, the mean TIMI flow grade increased from 1.2 +/- 1.1 before treatment to 2.3 +/- 1.0 after treatment (P < 0.0001); the mean TIMI thrombus grade decreased from 3.2 +/- 1.0 before treatment to 1.6 +/- 1.4 after treatment (P < 0.0001). Complications included bleeding (9.2%), MI (17.6%), need for coronary artery bypass grafting (CABG) (9.2%), need for repeat PTCA/atherectomy/stents (4.9%), and ventricular fibrillation (1.7%, all associated with opening totally occluded vessels). There were 14 subsequent in-hospital deaths: 13 of the patients who died had originally presented with MI; the other had experienced abrupt vessel closure during a PTCA procedure. Intracoronary t-PA appears to be effective in improving distal flow and decreasing thrombus burden; however, intracoronary delivery of t-PA has associated risks.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardium at risk and infarct size after thrombolytic therapy for acute myocardial infarction: implications for the design of randomized trials of acute intervention

OBJECTIVES

The purpose of this study was to estimate the effect of an improved reperfusion therapy for acute myocardial infarction on myocardial salvage and ventricular function for anterior and inferior infarctions and to ascertain the sample size required to detect such an effect.

BACKGROUND

There are significant differences in myocardium at risk between anterior and inferior infarctions that affect the benefit of reperfusion therapy.

METHODS

We studied 58 patients with acute myocardial infarction (24 anterior, 34 inferior) treated with intravenous recombinant tissue-type plasminogen activator and angioplasty when necessary. Tomographic imaging with technetium-99m sestamibi was performed to measure myocardium at risk, final infarct size and myocardial salvage and to estimate the beneficial effects of an improved therapy.

RESULTS

A new therapy that was 30% more effective than existing therapy (with respect to salvage) would increase salvage (and reduce mean infarct size) by 5.2% of the left ventricle and increase late ejection fraction by only 0.012 (95% confidence interval [CI] 0.009 to 0.015) in inferior infarction and by 0.038 (95% CI 0.027 to 0.047) in anterior infarction. If anterior and inferior infarctions occurred with equal frequency, a sample size of 140 patients in each treatment group would be required to detect such a change with 80% power. In a trial of interior infarctions alone, a sample size of 236 patients in each treatment group would be required compared with only 98 patients in a trial of anterior infarctions alone.

CONCLUSIONS

The anticipated mean benefit from an improved reperfusion therapy in individual patients with inferior infarction is very small and of questionable clinical significance. The anticipated benefit in anterior infarction is greater and easier to detect. Future randomized trials should be stratified for infarct location and should consider the greater absolute benefit of treatment in anterior infarction.

Progressive decreases in coronary vein flow during reperfusion in acute myocardial infarction: clinical documentation of the no reflow phenomenon after successful thrombolysis

OBJECTIVES

This study was undertaken to examine the effects of coronary flow dynamics after thrombolysis on infarct size limitation.

BACKGROUND

It has been commonly accepted that early thrombolysis does not necessarily salvage infarcted myocardium. Plausible causes for myocardial necrosis include such factors as elapsed time to reperfusion, residual stenosis, collateral vessels, hemodynamic loads, preconditioning and reperfusion injury. Recently, the no reflow phenomenon has been elucidated to be associated with infarct extension in clinical studies employing contrast echocardiography or thallium scintigraphy.

METHODS

Nineteen patients with early reperfusion in acute anterior myocardial infarction and comparable clinical background were studied. The patients were classified into two groups on the basis of pattern of thermodilution measurements of great cardiac vein flow after reperfusion: group A, 9 patients with a progressive decrease in great cardiac vein flow during the 1st 24 h of the onset of infarction; and group B, 10 patients without this observation. Left ventricular ejection fraction and thallium perfusion defect were compared between the two groups at follow-up.

RESULTS

There were no significant differences in systemic hemodynamic variables between groups A and B, and neither group had recurrent ischemic events suggesting reocclusion or restenosis during the study. In group A, both great cardiac vein flow (mean +/- SD 44 +/- 17% reduction) and oxygen extraction (38 +/- 15% reduction) were progressively decreased after the onset of reperfusion. Compared with group B, this group showed a lower left ventricular ejection fraction (36 +/- 7% vs. 63 +/- 15%, p < 0.01) and a larger thallium-201 defect severity index (1,091 +/- 366 U vs. 247 +/- 261 U, p < 0.01) at follow-up. Although other patient characteristics were comparable between the two groups, antecedent angina occurred in 90% of group B patients in contrast to only 33% of group A patients.

CONCLUSIONS

Salvage of myocardium from infarction by successful thrombolysis was not observed in the patients demonstrating progressive decreases in great cardiac vein flow (group A). In those patients, inadequate myocardial reperfusion on a microvascular basis might be associated with a much larger myocardial infarction. Antecedent angina may protect against a progressive decrease in coronary flow and may have beneficial effects on infarct size limitation.

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.

Late reperfusion for acute myocardial infarction limits the dilatation of left ventricle without the reduction of infarct size

BACKGROUND

While previous clinical studies have shown a possible beneficial effect of the reperfusion performed at a relatively late phase of acute myocardial infarction ("late reperfusion") in preventing left ventricular enlargement, the mechanism has not been clarified.

METHODS AND RESULTS

Of 89 patients with an initial anterior myocardial infarction, reperfusion was successful in 69. These 69 were divided into three groups according to the time required to achieve reperfusion after the onset of symptoms: early-reperfused (< 3 hours from the onset to reperfusion; n = 22), intermediate-reperfused (3 to 6 hours from the onset to reperfusion; n = 28), and late-reperfused (> 6 hours from the onset to reperfusion; n = 19). The 20 patients whose infarct-related artery were occluded in the acute phase as well as 1 month later was classified as nonreperfused. Infarct size, evaluated as defect volume by 201Tl single-photon emission computed tomography 1 month after the onset, was 1593 +/- 652 units (mean +/- SD) in the late-reperfused group, significantly larger (P < .05) than that of the intermediate-reperfused (1066 +/- 546 U) or the early-reperfused groups (372 +/- 453 U) but not different from that of the nonreperfused group (1736 +/- 562 U). Wall motion abnormality index as well as global ejection fraction evaluated by left ventriculography 1 month after the onset showed that late reperfusion did not preserve the left ventricular wall motion and function. These results indicate that the earlier reperfusion decreased the size of the infarction and preserved left ventricular function, whereas late reperfusion (> 6 hours after onset) did not limit infarct size or preserve left ventricular function. In contrast, the end-diastolic volume index did not differ significantly among the early-reperfused (50 +/- 15 mL/m2), intermediate-reperfused (54 +/- 14 mL/m2), and late-reperfused (53 +/- 19 mL/m2) groups; those were significantly smaller than that of the nonreperfused group (68 +/- 12 mL/m2; P < .05). Left ventriculographic data obtained in both the acute and chronic phase in 39 patients showed that left ventricular volumes increased significantly during the course of myocardial infarction only in the nonreperfused group.

CONCLUSIONS

Late reperfusion appeared to prevent ventricular dilatation acute myocardial infarction independent of the limitation of infarct size.

Clinical course and left ventricular function in patients with acute myocardial infarction following delayed recanalization of infarct-related artery

The effect of delayed recanalisation of the infarct related artery on clinical course and left ventricular functions was studied in 23 patients with acute myocardial infarction (Group 2). Another 82 patients with acute myocardial infarction served as controls: 48 patients with immediate recanalisation of the infarct related artery following intracoronary thrombolytic therapy (Group 1) and 34 patients with unsuccessful thrombolysis with the artery remaining occluded on repeat angiography (Group 3). Baseline clinical characteristics and left ventricular ejection fractions in the three groups did not differ statistically. Following intracoronary thrombolysis the clinical features and left ventricular functions in the three groups, respectively were as follows: post infarction angina--45.8%, 13.1% and 11.8% (1 vs. 2 and 3, P < 0.05); reinfarction--29.2%, 8.7% and 11.8% (1 vs. 2 and 3, P < 0.05); mortality--0%, 0% and 11.8% (1 and 2 vs. 3; P < 0.05); aneurysm--16.7%, 21.7% and 52.9% (1 and 2 vs. 3, P < 0.05); heart failure--20.8%, 21.7% and 47.1% (1 and 2 vs. 3, P < 0.05). Left ventricular ejection fractions on the second and on days 10-14 were, respectively, 47.6 +/- 1.1%, 42.8 +/- 1.1% and 39.2 +/- 1.6% (1 vs. 2 and 3, P < 0.05) and --52.1 +/- 1.0%, 48.9 +/- 1.1% and 44.3 +/- 1.5% (1 and 2 vs. 3, P < 0.05). Thus following delayed recanalisation of the infarct related artery the clinical course and left ventricular function improved significantly in comparison to patients without recanalisation.

Long-term follow-up of global and regional left ventricular function by two-dimensional echocardiography after thrombolytic therapy in acute myocardial infarction

In order to evaluate changes in left ventricular volumes and regional left ventricular function after thrombolytic therapy in acute myocardial infarction serial two-dimensional echocardiography was performed during a follow-up of 2 years in 206 consecutive patients treated with streptokinase and adjunctive angioplasty in a randomized group of patients. Unexpected progressive left ventricular enlargement was detected both with and without angioplasty. In anterior wall infarction, end-diastolic volume index increased from 55 +/- 14 to 91 +/- 28 ml/m2 (+65%, P < 0.01) and end-systolic volume index increased from 31 +/- 11 to 55 +/- 23 ml/m2 (+79%, P < 0.01), whereas ejection fraction decreased from 45 +/- 9 to 41 +/- 7% (-9%, P = NS). Averaged regional anterior wall motion improved during the first 4 weeks (11 +/- 10 to 16 +/- 12%), but subsequently deteriorated (16 +/- 12 to 10 +/- 6, P < 0.05). The number of segments with pathological wall motion increased. Similar volumetric and regional wall motion data were demonstrated in inferior wall infarction. We believe this reflects a chronic ventricular remodelling phenomenon. This process takes place predominantly during the first 3 months, but continues over the whole follow-up period. Forty percent of the patients suffered symptoms of heart failure on long-term follow-up. Attenuation of progressive ventricular enlargement remains a therapeutic challenge in the long-term care of these patients. Angiotensin-converting enzyme inhibitors are promising agents in this regard.

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)

A prospective, placebo-controlled, randomized trial of intravenous streptokinase and angioplasty versus lone angioplasty therapy of acute myocardial infarction

BACKGROUND

The value of routine administration of intravenous thrombolytic agents during percutaneous transluminal coronary angioplasty (PTCA) therapy of acute myocardial infarction (MI) has not been determined. Therefore, we prospectively randomized 122 patients with evolving MI to PTCA therapy with or without adjunctive intravenous streptokinase therapy.

METHODS AND RESULTS

Patients with ECG ST segment elevation who presented within 4 hours of symptom onset, had no contraindication to thrombolytic therapy, and were not in cardiogenic shock were enrolled. They were treated immediately with intravenous heparin (10,000 units) and oral aspirin (325 mg) and randomized to treatment with placebo or streptokinase (1.5 M units) administered intravenously over 30 minutes. Patients then were taken immediately to the catheterization laboratory, and those with suitable coronary anatomy underwent immediate PTCA. Subsequent clinical course, serial radionuclide ventriculography, and 6-month repeat angiography were analyzed. A total of 106 patients were treated with PTCA. Use of PTCA was similar for placebo (92%) and streptokinase (83%) groups. Angioplasty was successful in 95% of patients, with no difference in placebo (93%) and streptokinase (98%) groups. Serial radionuclide ventriculography demonstrated no difference in 24-hour (52 +/- 12% versus 50 +/- 12%) or 6-week (51 +/- 12% versus 51 +/- 13%) ejection fraction values for placebo and streptokinase groups, respectively. Contrast ventriculography demonstrated improvement in immediate (54 +/- 12%) versus 6-month (60 +/- 15%, p < 0.05) values for the overall group. No differences in 6-month values were present (58 +/- 15% versus 62 +/- 15%, p = NS) for placebo and streptokinase groups, respectively. Coronary angiography was performed in 75% of the 90 patients eligible for restudy. Arterial patency was 87% at 6 months, and coronary restenosis was present in 38% of patients. No differences in chronic patency or restenosis were detected for the two treatment groups. Although adjunctive intravenous streptokinase therapy did not improve outcome, it did complicate the hospital course. Hospitalization was longer (9.3 +/- 5.0 versus 7.7 +/- 4.4 days, p = 0.046) and more costly ($25,191 +/- 15,368 versus $19,643 +/- 7,250, p < 0.02). Transfusion rate was higher (39% versus 8%, p = 0.0001) and need for emergency coronary bypass surgery was greater (10.3% versus 1.6%, p = 0.03) for the streptokinase-treated patients.

CONCLUSIONS

Adjunctive intravenous streptokinase therapy does not enhance early preservation of ventricular function, improve arterial patency rates, or lower restenosis rates after PTCA therapy of acute MI. Hospital course is longer, more expensive, and more complicated. For these reasons, PTCA therapy of acute MI should not be routinely performed with adjunctive intravenous streptokinase therapy.

Association of patency of the infarct-related coronary artery with plasma levels of plasminogen activator inhibitor activity in acute myocardial infarction

To examine the fibrinolytic capacity in patients with acute myocardial infarction (AMI), baseline levels of plasma plasminogen activator inhibitor (PAI) activity and tissue-type plasminogen activator (t-PA) antigen were measured in 47 patients with Q-wave AMI who underwent emergent coronary angiography 3.0 +/- 0.2 hours after the symptom onset. They received intracoronary injection of urokinase if their infarct-related arteries were occluded. They were classified into 3 groups according to the patency of the infarct-related artery before and after thrombolytic therapy: the patent group (13 patients), the recanalized group (23 patients) and the occluded group (11 patients). The mean level of plasma PAI activity (IU/ml) was higher in patients with AMI as a whole than in the control group (12.8 +/- 1.6 vs 5.4 +/- 0.5, p less than 0.01). The level was lower in the patent group (3.0 +/- 1.1) and higher in the recanalized (18.6 +/- 2.2) and occluded (10.8 +/- 2.5) groups than in the control group (each p less than 0.01). The level was lower in the occluded than in the recanalized group (p less than 0.01) and 62% of the patients in the occluded group had levels within range of the control group. The mean level of plasma t-PA antigen (ng/ml) was higher in patients with AMI as a whole than in the control group (10.3 +/- 0.8 vs 5.8 +/- 0.3, p less than 0.01). There was no difference in the level among the 3 groups with AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Technetium 99m sestamibi in the assessment of acute myocardial infarction

Technetium 99m sestamibi is a promising new radiopharmaceutical that can assess myocardium at risk, infarct size, and treatment efficacy in acute myocardial infarction. The minimal redistribution of this radiopharmaceutical makes it ideal for the measurement of myocardium at risk, as demonstrated by several animal studies. The high-count density images are readily quantitated, and techniques have been developed and validated for this purpose. Early clinical studies have shown that myocardium at risk varies widely, even for a coronary occlusion in a similar location, a finding similar to that reported previously in several different animal infarction models. The clinical use of this radiopharmaceutical to measure final infarct size and treatment benefit, or myocardial salvage, has now been demonstrated using both planar and tomographic imaging techniques. Evidence of benefit is often evident by 18 to 48 hours after reperfusion therapy, although the full extent of improvement is not evident until later. The current 6-hour shelf life and 30-minute preparation time are logistical barriers to widespread clinical use. This radiopharmaceutical provides a new, powerful measurement tool for the assessment of treatment efficacy in acute myocardial infarction that is probably superior to other currently available methods.

Effects of time required for reperfusion (thrombolysis or angioplasty, or both) and location of acute myocardial infarction on left ventricular functional reserve capacity several months later

The purpose of this study was to determine whether reperfusion of acute myocardial infarction (AMI) by recombinant tissue-type plasminogen activator (rt-PA) or percutaneous transluminal coronary angioplasty, or both, would improve left ventricular (LV) function when it is measured several months later at rest or maximal bicycle exercise, or both. Radionuclide angiography was performed in 44 patients 5 months (range 6 weeks to 9 months) after AMI to assess function, and tomographic myocardial thallium-201 imaging was performed at maximal exercise and delayed rest to determine whether there was any evidence of myocardial ischemia. As expected, no patient had chest pain or redistribution of a thallium defect during the exercise test, because patients had undergone angioplasty (n = 28) or coronary bypass graft surgery (n = 5) where clinically indicated for revascularization. The LV ejection fraction was plotted as a function of the time elapsed between the onset of chest pain and the time when coronary angiography confirmed patency of the infarct-related artery (achieved in 91% of 44 patients by rt-PA [n = 31] or percutaneous transluminal coronary angioplasty [n = 9] ). Functional responses differed markedly between patients with anterior (n = 20) versus inferior (n = 24) wall AMI. LV ejection fraction during exercise correlated with time to reperfusion in patients with an anterior wall AMI (r = -0.58; standard error of the estimate = 11.9%; p less than 0.02) but not in patients with an inferior AMI (r = 0.10; standard error of the estimate = 13.1%; difference not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of coronary angiographic features and oral dipyridamole thallium 201 tomography

Coronary angiography and left ventriculography is commonly used to identify those patients with incomplete infarctions and therefore, a need for revascularization. The authors compared coronary angiography and left ventriculography with thallium 201 tomography using oral dipyridamole to identify patients with potential ischemia in the infarct zone indicating viable tissue. Forty-five patients (37 men, 8 women) with acute myocardial infarctions (29 anterior, 16 inferior) who received intravenous thrombolytic therapy were studied. On the basis of the left ventriculograms, only 16 patients were judged to have residual function in the infarct zone. Six of these patients had no thallium redistribution in the infarct zone, indicating lack of residual ischemia. Of the 29 patients with no residual function in the infarct zone, 18 had redistribution in the infarct zone, suggesting residual ischemic myocardium and thus viable tissue. Among the 32 patients with open infarct vessels, 15 had no redistribution in the infarct zone, but of the remaining 13 patients with occluded infarct vessels, 9 had redistribution in the infarct zone indicating residual ischemia and thus viable tissue. The authors' data suggest that neither wall motion analysis by left ventriculography nor the angiographic status of the infarct vessel identifies those patients with residual ischemia as evidenced by thallium tomography using oral dipyridamole.

Primary angioplasty in myocardial infarction: assessment of improved myocardial perfusion with technetium-99m isonitrile

Technetium-99m-hexakis-2-methoxy-2-isobutyl-isonitrile (technetium-99m isonitrile) is a new radiopharmaceutical compound that reflects myocardial perfusion. Its kinetics, especially its lack of redistribution after intravenous administration, permits the assessment of changes in myocardial perfusion without delay of therapy. Tomographic images at rest were obtained immediately and 6 to 10 days later in 17 consecutive patients undergoing successful primary angioplasty during their first transmural myocardial infarction. Thirteen patients had anterior infarction. The initial (acute) defect size before angioplasty of 48 +/- 17% of the left ventricle decreased significantly (p less than 0.0001) to 29 +/- 19% on the late scans. There was no correlation between the time to therapy and the reduction in defect size. Twelve of the 17 patients, including 7 of the 11 patients treated after 4 h, demonstrated a definite reduction in the initial defect size. Eight patients with angiographically proved persistent coronary occlusion underwent a similar imaging sequence. The initial defect size in this group remained unchanged on the late scans (24 +/- 16% versus 26 +/- 18%, p = NS). Primary angioplasty is an effective approach toward salvaging myocardium; comparison with thrombolytic drug therapy must await the results of controlled clinical trials.

Holter monitoring of ventricular arrhythmias in a randomised, controlled study of intravenous streptokinase in acute myocardial infarction

The occurrence of ventricular arrhythmias attributed to streptokinase treatment in acute myocardial infarction is not well defined. Holter monitoring was performed for 24 hours in 81 patients with suspected acute myocardial infarction randomised in a ratio of 2:1 to intravenous streptokinase 1.5 x 10(6) IU (n = 55) or placebo infusion (n = 26) 6.7 hours (mean) after the onset of symptoms. No episodes of ventricular fibrillation were recorded. For the whole 24 hour period and during the first three hours after the start of treatment the incidence and frequency of ventricular arrhythmias were similar in the patients randomised to streptokinase and to placebo. But when the results in patients randomised "early" after the onset of symptoms of suspected acute myocardial infarction were analysed separately the frequency of abnormal complexes, pairs, runs, and repetitive arrhythmias seemed to be higher in patients allocated to streptokinase. This may reflect arrhythmias associated with reperfusion.

Effect of streptokinase on prostacyclin synthesis and phospholipase activity in cultured pulmonary artery endothelial cells

In this study, we examined the effects of streptokinase on arachidonic acid release and prostacyclin biosynthesis in cultured bovine pulmonary artery endothelial cells. When intact cells were incubated with streptokinase, a significant stimulatory effect on prostacyclin biosynthetic activity in cells was evident without any cellular damage at all concentrations used (1-10,000 units/ml). Streptokinase also caused a marked release of arachidonic acid. It induced rapid phospholipid hydrolysis, resulting in the release of up to 15% of incorporated [3H]arachidonic acid into the medium. After the addition of streptokinase, degradation of phosphatidylcholine and phosphatidylethanolamine was observed and lysophosphatidylcholine and lysophosphatidylethanolamine were produced. We also observed a transient rise in diacylglycerol after the addition of streptokinase. To test for phospholipase C activity, the release of incorporated [3H]choline, [3H]inositol and [3H]ethanolamine into the culture medium was determined. The level of radioactive inositol showed an increase, but the changes in choline and ethanolamine were comparatively small. An increase in inositol was detectable within 1 min after streptokinase addition and peaked after 15 min. Inositol phosphate and inositol trisphosphate were released, and these releases were suppressed by the addition of neomycin (50 microM). These results suggest that streptokinase stimulates phospholipase A2 and C activity, and that prostacyclin biosynthesis is subsequently increased in cultured endothelial cells.

Cardiac rupture, mortality and the timing of thrombolytic therapy: a meta-analysis

This study examined the relation between the risk of cardiac rupture and the timing of thrombolytic therapy for acute myocardial infarction. To test the hypothesis that cardiac rupture is prevented by early thrombolytic therapy but is promoted by late treatment, randomized controlled trials of thrombolytic agents for myocardial infarction were pooled. A logistic regression model including 58 cases of cardiac rupture among 1,638 patients from four trials showed that the odds ratio (treated/control) of cardiac rupture was directly correlated with time to treatment (p = 0.01); at 7 h, the odds ratio was 0.4 (95% confidence limits 0.17 to 0.93); at 11 h, it was 0.93 (0.53 to 1.60) and at 17 h, it was 3.21 (1.10 to 10.1). Analysis of data from the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) trial independently confirmed the relation between time to thrombolytic therapy and risk of cardiac rupture (p = 0.03). Analysis of 4,692 deaths in 44,346 patients demonstrated that the odds ratio of death was also directly correlated with time to treatment (p = 0.006); at 3 h, the odds ratio for death was 0.72 (0.67 to 0.77); at 14 h, it was 0.88 (0.77 to 1.00) and at 21 h, it was 1 (0.82 to 1.37). Thrombolytic therapy early after acute myocardial infarction improves survival and decreases the risk of cardiac rupture. Late administration of thrombolytic therapy also appears to improve survival but may increase the risk of cardiac rupture.

Optimal utilization of thrombolytic therapy for acute myocardial infarction: concepts and controversies

Timely administration of thrombolytic therapy decreases myocardial infarct size, lessens the incidence of congestive heart failure and improves survival. However, available data suggest that only 10% of patients with acute infarction in the United States receive thrombolytic drugs. Given the benefits of thrombolytic therapy, all patients with myocardial infarction would likely be treated were it not for associated risks. Several groups exist in which the risk/benefit ratio of thrombolytic therapy continues to be controversial, including those with inferior infarction, absence of ST segment elevation or presentation greater than 6 h from symptom onset, elderly patients and those with hypertension. Three recent thrombolytic trials reported a reduction in mortality that was entirely independent of infarct location. Pooled data from trials involving 12,000 patients with inferior infarction have demonstrated a reduction in mortality rate (6.8% versus 8.7%, p less than 0.0001). Furthermore, improvement in regional and global left ventricular function occurred after reperfusion therapy of inferior infarction. Pooled data indicate that patients treated between 6 and 24 h after symptom onset have a lower mortality rate than do those who receive placebo (11.1% versus 13.1%, p less than 0.001). Improved survival occurs after thrombolytic therapy in patients with ST segment elevation or left bundle branch block, but not in those with isolated ST depression or a normal electrocardiogram. Age should not be considered an absolute contraindication because the lifesaving potential of thrombolytic therapy in the elderly may be two to three times that of the overall group of patients with myocardial infarction. Finally, recent studies demonstrated that patients who present with hypotension or hypertension or who have undergone cardiopulmonary resuscitation may also benefit.(ABSTRACT TRUNCATED AT 250 WORDS)

The signal-averaged electrocardiogram and ventricular arrhythmias after thrombolysis for acute myocardial infarction

The prevalence of an abnormal signal-averaged electrocardiogram (ECG) and ventricular arrhythmias on 24 h ambulatory electrocardiography was evaluated in 118 patients 13 +/- 2 days after acute myocardial infarction. Group 1 (46 patients) underwent intravenous thrombolysis within 6 h of the onset of symptoms, whereas Group 2 (72 patients) did not. An abnormal signal-averaged ECG was seen in 15% of patients in Group 1 and 21% of those in Group 2 (difference not significant). The number of ventricular premature complexes/h was lower in Group 1 than in Group 2: 2.58 +/- 1.63 versus 7.91 +/- 10.75 (p less than 0.01). However, complex arrhythmias (greater than or equal to 10 ventricular premature complexes/h or ventricular tachycardia) were equally common in Groups 1 and 2 (20% versus 22%, respectively). Their prevalence was similar in patients with or without an abnormal signal-averaged ECG (29% versus 18%, respectively, in Group 1 and 27% versus 21%, respectively, in Group 2). Comparison between patients with (n = 26) or without (n = 20) angiographic patency of the infarct-related coronary artery after thrombolysis showed no significant difference in the prevalence of an abnormal signal-averaged ECG (8% versus 25%, respectively) and complex ventricular arrhythmias (19% versus 20%, respectively). These data suggest that thrombolysis does not affect the prevalence of complex ventricular arrhythmias and an abnormal signal-averaged ECG or their relation after acute myocardial infarction.

Comparison of contrast angiography and two-dimensional echocardiography for the evaluation of left ventricular regional wall motion abnormalities after acute myocardial infarction

Regional left ventricular wall motion abnormalities were assessed using 2-dimensional echocardiography and contrast ventriculography within 12 hours of the onset of chest pain in 20 patients with acute myocardial infarction (AMI); 10 patients had anterior infarctions and 10 had inferior. End-diastolic and end-systolic sinus beats from right anterior oblique contrast ventriculograms were analyzed using the center-line chord technique with both a standard overlap method of chord assignment and a nonoverlap method. Echocardiograms were obtained in parasternal long- and short-axis and apical 2- and 4-chamber views and analyzed using a 16-segment scoring system to derive anterior and infero-posterolateral wall motion indexes using both overlap (10 segments for anterior, 8 inferior) as well as nonoverlap (9 segments anterior, 7 inferior) methods of segment assignment. There was a significant inverse correlation between the standard (nonoverlap) echocardiographic analysis and the standard (overlap) angiographic analysis for infarct regions (y = -0.43 X +1.11, r = -0.59, p less than 0.05). Fifteen of 18 patients with angiographic infarct regional score less than or equal to -1 standard deviation/chord had an echocardiographic index greater than or equal to 1.5, while 15 of 16 patients with echocardiographic regional infarct index greater than or equal to 1.5 had an angiographic score less than or equal to -1 standard deviation/chord. Correlation between the 2 methods for noninfarct territories was poor (r = -0.34) because the angiographic method assesses hyperkinesis while the echocardiographic method does not.(ABSTRACT TRUNCATED AT 250 WORDS)