Safety assessment of single-bolus administration of TNK tissue-plasminogen activator in acute myocardial infarction: the ASSENT-1 trial. The ASSENT-1 Investigators

Mortality Outcomes with Tenecteplase Versus Alteplase in the Treatment of Massive Pulmonary Embolism

BACKGROUND

Pulmonary embolism (PE) leads to many emergency department visits annually. Thrombolytic agents, such as alteplase, are currently recommended for massive PE, but genetically modified tenecteplase (TNK) presents advantages. Limited comparative studies exist between TNK and alteplase in PE treatment.

OBJECTIVE

The aim of this study was to assess the safety and mortality of TNK compared with alteplase in patients with PE using real-world evidence obtained from a large multicenter registry. Primary outcomes included mortality, intracranial hemorrhage, and blood transfusions.

METHODS

This retrospective cohort study used the TriNetX Global Health Research Network. Patients aged 18 years or older with a PE diagnosis (International Classification of Diseases, 10th Revision, Clinical Modification code I26) were included. The following two cohorts were defined: TNK-treated (29 organizations, 266 cases) and alteplase-treated (22,864 cases). Propensity matching controlled for demographic characteristics, anticoagulant use, pre-existing conditions, and vital sign abnormalities associated with PE severity. Patients received TNK or alteplase within 7 days of diagnosis and outcomes were measured at 30 days post thrombolysis.

RESULTS

Two hundred eighty-three patients in each cohort were comparable in demographic characteristics and pre-existing conditions. Mortality rates at 30 days post thrombolysis were similar between TNK and alteplase cohorts (19.4% vs 19.8%; risk ratio 0.982; 95% CI 0.704-1.371). Rates of intracerebral hemorrhages and transfusion were too infrequent to analyze.

CONCLUSIONS

This study found TNK to exhibit a similar mortality rate to alteplase in the treatment of PE with hemodynamic instability. The results necessitate prospective evaluation. Given the cost-effectiveness and ease of administration of TNK, these findings contribute to the ongoing discussion about its adoption as a primary thrombolytic agent for stroke and PE.

Mortality outcomes and predictors of failed thrombolysis following STEMI thrombolysis in a non-PCI capable tertiary hospital: a 5-year analysis

Pharmacological reperfusion remains the primary strategy for ST-elevation myocardial infarction (STEMI) in low- and medium-income countries. Literature has reported inconsistent incidences and outcomes of failed thrombolysis (FT). This study aimed to identify the incidence, mortality outcomes and predictors of FT in STEMI pharmacological reperfusion. This single-centre retrospective cohort study analyzed data on consecutive STEMI patients who received thrombolytic therapy from 2016 to 2020 in a public tertiary hospital. Total population sampling was used in this study. Logistic regression analyses were used to assess independent predictors of the mortality outcomes and FT. We analyzed 941 patients with a mean age of 53.0 ± 12.2 years who were predominantly male (n = 846, 89.9%). The in-hospital mortality was 10.3% (n = 97). FT occurred in 86 (9.1%) patients and was one of the predictors of mortality (aOR 3.847, p < 0.001). Overall, tenecteplase use (aOR 1.749, p = 0.021), pre-existing hypertension (aOR 1.730, p = 0.024), history of stroke (aOR 4.176, p = 0.004), and heart rate ≥ 100 bpm at presentation (aOR 2.333, p < 0.001) were the general predictors of FT. The predictors of FT with streptokinase were Killip class ≥ II (aOR 3.197, p = 0.004) and heart rate ≥ 100 bpm at presentation (aOR 3.536, p = 0.001). History of stroke (aOR 6.144, p = 0.004) and heart rate ≥ 100 bpm at presentation (aOR 2.216, p = 0.015) were the predictors of FT in STEMI patients who received tenecteplase. Mortality following STEMI thrombolysis remained high in our population and was attributed to FT. Identified predictors of FT enable early risk stratification to evaluate the patients' prognosis to manage them better.

Fibrinolytic Therapy in Patients with Acute ST-elevation Myocardial Infarction

Fibrinolytic agents provide an important alternative therapeutic strategy in individuals presenting with ST-elevation myocardial infarction (STEMI). Ultimately, primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for most patients with STEMI, including elderly patients and patients with coronavirus disease 2019 (COVID-19) infection. Fibrinolytic therapy should always be considered when timely primary PCI cannot be delivered appropriately. Clinicians should promptly recognize the signs of fibrinolytic therapy failure and consider rescue PCI. When fibrinolytics are used, coronary angiography and revascularization should not be conducted within the initial 3 hours after fibrinolytic administration.

Tenecteplase Thrombolysis for Acute Ischemic Stroke

Tenecteplase is a fibrinolytic drug with higher fibrin specificity and longer half-life than the standard stroke thrombolytic, alteplase, permitting the convenience of single bolus administration. Tenecteplase, at 0.5 mg/kg, has regulatory approval to treat ST-segment-elevation myocardial infarction, for which it has equivalent 30-day mortality and fewer systemic hemorrhages. Investigated as a thrombolytic for ischemic stroke over the past 15 years, tenecteplase is currently being studied in several phase 3 trials. Based on a systematic literature search, we provide a qualitative synthesis of published stroke clinical trials of tenecteplase that (1) performed randomized comparisons with alteplase, (2) compared different doses of tenecteplase, or (3) provided unique quantitative meta-analyses. Four phase 2 and one phase 3 study performed randomized comparisons with alteplase. These and other phase 2 studies compared different tenecteplase doses and effects on early outcomes of recanalization, reperfusion, and substantial neurological improvement, as well as symptomatic intracranial hemorrhage and 3-month disability on the modified Rankin Scale. Although no single trial prospectively demonstrated superiority or noninferiority of tenecteplase on clinical outcome, meta-analyses of these trials (1585 patients randomized) point to tenecteplase superiority in recanalization of large vessel occlusions and noninferiority in disability-free 3-month outcome, without increases in symptomatic intracranial hemorrhage or mortality. Doses of 0.25 and 0.4 mg/kg have been tested, but no advantage of the higher dose has been suggested by the results. Current clinical practice guidelines for stroke include intravenous tenecteplase at either dose as a second-tier option, with the 0.25 mg/kg dose recommended for large vessel occlusions, based on a phase 2 trial that demonstrated superior recanalization and improved 3-month outcome relative to alteplase. Ongoing randomized phase 3 trials may better define the comparative risks and benefits of tenecteplase and alteplase for stroke thrombolysis and answer questions of tenecteplase efficacy in the >4.5-hour time window, in wake-up stroke, and in combination with endovascular thrombectomy.

Evidence that Tenecteplase Is Noninferior to Alteplase for Acute Ischemic Stroke: Meta-Analysis of 5 Randomized Trials

Background and Purpose- TNK (tenecteplase), a newer fibrinolytic agent, has practical delivery advantages over ALT (alteplase) that would make it a useful agent if noninferior in acute ischemic stroke treatment outcome. Accordingly, the most recent US American Heart Association/American Stroke Association acute ischemic stroke guideline recognized TNK as an alternative to ALT, but only based on informal consideration, rather than formal meta-analysis, of completed randomized control trials. Methods- Systematic literature search and formal meta-analysis were conducted per PRISMA guidelines (Preferred Reporting Items for Systemic Reviews and Meta-Analyses), adapted to noninferiority analysis. The primary outcome of freedom from disability (modified Rankin Scale score, 0-1) outcome at 3 m, and additional efficacy and safety outcomes, were analyzed. Results- Systematic search identified 5 trials enrolling 1585 patients (828 TNK, 757 ALT). Across all trials, mean age was 70.8, 58.5% male, baseline National Institutes of Health Stroke Scale mean 7.0, and time from last known well to treatment start mean 148 minutes. All ALT patients received standard 0.9 mg/kg dosing, while TNK dosing was 0.1 mg/kg in 6.8%, 0.25 mg/kg in 24.6%, and 0.4 mg/kg in 68.6%. For the primary end point, crude cumulative rates of disability-free (modified Rankin Scale score, 0-1) 3 m outcome were TNK 57.9% versus ALT 55.4%. Informal, random-effects meta-analysis, the risk difference was 4% (95% CI, -1% to 8%). The lower 95% CI bound fell well within the prespecified noninferiority margin. Similar results were seen for the additional efficacy end points: functional independence (modified Rankin Scale score, 0-2): crude TNK 71.9% versus ALT 70.5%, risk difference 2% (95% CI, -3% to 6%); and modified Rankin Scale shift analysis, common odds ratio 1.21 (95% CI, 0.93-1.57). For safety end points, lower event rates reduced power, but point estimates were also consistent with noninferiority Conclusions- Accumulated clinical trial data provides strong evidence that TNK is noninferior to ALT in the treatment of acute ischemic stroke. These findings provide formal support for the recent guideline recommendation to consider TNK an alternative to ALT.

The evolution of recombinant thrombolytics: Current status and future directions

Cardiovascular disorders are on the rise worldwide due to alcohol abuse, obesity, hypertension, raised blood lipids, diabetes and age-related risks. The use of classical antiplatelet and anticoagulant therapies combined with surgical intervention helped to clear blood clots during the inceptive years. However, the discovery of streptokinase and urokinase ushered the way of using these enzymes as thrombolytic agents to degrade the fibrin network with an issue of systemic hemorrhage. The development of second generation plasminogen activators like anistreplase and tissue plasminogen activator partially controlled this problem. The third generation molecules, majorly t-PA variants, showed desirable properties of improved stability, safety and efficacy with enhanced fibrin specificity. Plasmin variants are produced as direct fibrinolytic agents as a futuristic approach with targeted delivery of these drugs using liposome technlogy. The novel molecules from microbial, plant and animal origin present the future of direct thrombolytics due to their safety and ease of administration.

Therapeutic Potential of Tenecteplase in the Management of Acute Ischemic Stroke

Given that alteplase has been the only approved thrombolytic agent for acute ischemic stroke for almost two decades, there has been intense interest in more potent and safer agents over the last few years. Tenecteplase is a bioengineered mutation of alteplase with advantageous pharmacodynamics and pharmacokinetics. The superiority of tenecteplase over alteplase has been proven by in vitro and animal studies, and it was approved for use in myocardial infarction more than a decade ago. In patients with acute ischemic stroke, tenecteplase has shown promise in randomized phase II trials and the drug is currently being tested in four phase III clinical trials that will start delivering definite results in the near future: NOR-TEST (NCT01949948), TASTE (ACTRN12613000243718), TEMPO-2 (NCT02398656), and TALISMAN (NCT02180204).

Drug Treatment of STEMI in the Elderly: Focus on Fibrinolytic Therapy and Insights from the STREAM Trial

Elderly patients constitute a large and growing proportion of ST-elevation myocardial infarction (STEMI) patients, yet they have been under-represented or even excluded from reperfusion trials. Despite evidence that fibrinolysis improves outcomes irrespective of age, many elderly STEMI patients still remain undertreated or subject to major delays to primary percutaneous coronary intervention (PCI). The fear of an excessive risk of intracranial hemorrhage (ICH) in these patients can lead to avoidance of potentially life-saving reperfusion treatment, despite the fact that current STEMI guidelines do not exclude the elderly from a pharmaco-invasive strategy. Age-specific dose reductions have been succesfully made to antithrombotic drugs such as clopidogrel and enoxaparin as an adjunct to fibrinolysis, but until recently no dose adjustments for elderly patients have been applied to the fibrinolytic agents. In the pharmaco-invasive STREAM trial, halving the bolus of tenecteplase for patients aged >75 years because of an unacceptably high ICH rate in the elderly was associated with a more favorable safety/efficacy profile. Whether a pharmaco-invasive strategy including half-dose tenecteplase, age- and weight-adjusted enoxaparin, and a tailored P2Y12 inhibitor followed by routine angiography represents a safe and efficacious alternative reperfusion therapy for elderly patients remains to be prospectively assessed in a clinical trial in this age group.

Enzymes approved for human therapy: indications, mechanisms and adverse effects

Research and drug developments fostered under orphan drug product development programs have greatly assisted the introduction of efficient and safe enzyme-based therapies for a range of rare disorders. The introduction and regulatory approval of 20 different recombinant enzymes has enabled, often for the first time, effective enzyme-replacement therapy for some lysosomal storage disorders, including Gaucher (imiglucerase, taliglucerase, and velaglucerase), Fabry (agalsidase alfa and beta), and Pompe (alglucosidase alfa) diseases and mucopolysaccharidoses I (laronidase), II (idursulfase), IVA (elosulfase), and VI (galsulfase). Approved recombinant enzymes are also now used as therapy for myocardial infarction (alteplase, reteplase, and tenecteplase), cystic fibrosis (dornase alfa), chronic gout (pegloticase), tumor lysis syndrome (rasburicase), leukemia (L-asparaginase), some collagen-based disorders such as Dupuytren's contracture (collagenase), severe combined immunodeficiency disease (pegademase bovine), detoxification of methotrexate (glucarpidase), and vitreomacular adhesion (ocriplasmin). The development of these efficacious and safe enzyme-based therapies has occurred hand in hand with some remarkable advances in the preparation of the often specifically designed recombinant enzymes; the manufacturing expertise necessary for commercial production; our understanding of underlying mechanisms operative in the different diseases; and the mechanisms of action of the relevant recombinant enzymes. Together with information on these mechanisms, safety findings recorded so far on the various adverse events and problems of immunogenicity of the recombinant enzymes used for therapy are presented.

Current State of ST-Segment Myocardial Infarction: Evidence-based Therapies and Optimal Patient Outcomes in Advanced Systems of Care

Advances in reperfusion therapy for ST-segment elevation myocardial infarction (STEMI) provide optimal patient outcomes. Reperfusion therapies, including contemporary primary percutaneous coronary intervention, represent decades of clinical evidence development in large clinical trials and national databases. However, rapid identification of STEMI and guideline-directed management of patients across broad populations have been best achieved in advanced systems of care. Current outcomes in STEMI reflect the evolution of both clinical data and idealized health care delivery networks.

Ultraslow thrombolytic therapy: A novel strategy in the management of PROsthetic MEchanical valve Thrombosis and the prEdictors of outcomE: The Ultra-slow PROMETEE trial

BACKGROUND

Low-dose (25mg), slow infusion (6hours) of tissue-type plasminogen activator (t-PA) with repetition as needed has been shown to provide effective and safer thrombolysis in patients with prosthetic valve thrombosis (PVT). Further prolonging the infusion time may be rational with regard to reducing complication rates without reducing success rates. We aimed to investigate the efficacy and safety of ultraslow (25hours) infusion of low-dose (25mg) alteplase (t-PA) for PVT.

METHODS AND RESULTS

Transesophageal echocardiography-guided thrombolytic therapy (TT) was administered to 114 patients with PVT in 120 different episodes between 2009 and 2013 in a single center. Prosthetic valve thrombosis was obstructive in 77 (64.2%) and nonobstructive in 43 (35.8%) episodes. Ultraslow infusion (25hours) of low-dose (25mg) t-PA, as the TT regimen, was used in all patients admitted with PVT. The end points were thrombolytic success, mortality, and complication rates. The overall success rate of TT was 90% (95% CI 0.85-0.95). The univariate predictors of an unsuccessful result were higher New York Heart Association (NYHA) class, thrombus cross-sectional area, duration of suboptimal anticoagulation, lower baseline valve area, and presence of atrial fibrillation. The NYHA class was the only independent predictor of TT failure by multiple variable analysis. The overall complication rate was 6.7% (3.3% nonfatal major, 2.5% minor, and 0.8% death). The predictors of complications were presence of atrial fibrillation, higher NYHA class, and thrombus area.

CONCLUSION

Ultraslow (25hours) infusion of low-dose (25mg) t-PA without bolus appears to be associated with quite low nonfatal complications and mortality for PVT patients without loss of effectiveness, except for those with NYHA class IV.

Current state of ST-segment myocardial infarction: evidence-based therapies and optimal patient outcomes in advanced systems of care

Advances in reperfusion therapy for ST-segment elevation myocardial infarction (STEMI) provide optimal patient outcomes. Reperfusion therapies, including contemporary primary percutaneous coronary intervention, represent decades of clinical evidence development in large clinical trials and national databases. However, rapid identification of STEMI and guideline-directed management of patients across broad populations have been best achieved in advanced systems of care. Current outcomes in STEMI reflect the evolution of both clinical data and idealized health care delivery networks.

Risks and Benefits of Thrombolytic, Antiplatelet, and Anticoagulant Therapies for ST Segment Elevation Myocardial Infarction: Systematic Review

Objectives. Assess the impact of associating thrombolytics, anticoagulants, antiplatelets, and primary angioplasty (PA) on death, reinfarction (AMI), and major bleeding (MB) in STEMI therapy. Methods. Medline search was performed to identify randomized trials comparing these classes in STEMI treatment, at least 500 patients, providing death, AMI, and MB rates. Similar arms were grouped. Correlation between number of drugs and PA and the outcomes was evaluated, as well as correlation between the year of the study and the outcomes. Results. Fifty-nine papers remained after exclusions. 404.556 patients were divided into 35 groups of arms. There was correlation between the number of drugs and rates of death (r = -0.466, P = 0.005) and MB (r = 0.403, P = 0.016), confirmed by multivariate regression. This model also showed that PA is associated with lower mortality and increased MB. Year and period of publication correlated with the outcomes: death (r = -0.380, P < 0.001), MB (r = 0.212, P = 0.014), and AMI (r = -0.231, P = 0.009). Conclusion. The increasing complexity of STEMI treatment has resulted in significant reduction in mortality along with increased rates of MB. Overall, however, the benefits of treatment outweigh the associated risks of MB.

A prospective regional registry of ST-elevation myocardial infarction in Central Romania: impact of the Stent for Life Initiative recommendations on patient outcomes

BACKGROUND

Reperfusion therapy is the treatment of choice in patients with ST-elevation myocardial infarction (STEMI) presenting within 12 hours after the onset of symptoms. However, a significant number of patients do not benefit from it because of the lack of access to well-organized emergency care. We aimed to investigate the evolution of STEMI treatment and mortality between 2004 and 2011 in an unselected population from central Romania and to demonstrate the role of a regional network in increasing the rates of reperfusion therapy with associated reduction of STEMI-related mortality in a region with very low primary percutaneous coronary intervention (pPCI) rates at baseline.

METHODS

We analyzed the data of 5,899 consecutive patients with STEMI enrolled in this prospective study since 2004, after the initiation of an STEMI network in Central Romania and with continuous support of the Stent for Life Initiative.

RESULTS

Introduction of the network was associated with an absolute change in the use of reperfusion therapy from 2004 to 2011 (26.94% vs 87.15%, P < .001) and of pPCI (10.88% vs 78.64%, P < .001) for patients presenting within 12 hours after the onset of symptoms, with a decrease of inhospital mortality from 20.73% to 6.35% (P < .001). In addition, the global inhospital mortality of all the STEMI population showed a significant decrease (23.18% vs 13.39%, P < .001).

CONCLUSIONS

Reduction of STEMI-related mortality was possible via implementation of pPCI, even in a region with low health care expenditures. The organization of an STEMI network led to a significant decrease in STEMI-related mortality, revealing the significant impact of the Stent for Life Initiative recommendations on patient outcomes.

Proteases as therapeutics

Proteases are an expanding class of drugs that hold great promise. The U.S. FDA (Food and Drug Administration) has approved 12 protease therapies, and a number of next generation or completely new proteases are in clinical development. Although they are a well-recognized class of targets for inhibitors, proteases themselves have not typically been considered as a drug class despite their application in the clinic over the last several decades; initially as plasma fractions and later as purified products. Although the predominant use of proteases has been in treating cardiovascular disease, they are also emerging as useful agents in the treatment of sepsis, digestive disorders, inflammation, cystic fibrosis, retinal disorders, psoriasis and other diseases. In the present review, we outline the history of proteases as therapeutics, provide an overview of their current clinical application, and describe several approaches to improve and expand their clinical application. Undoubtedly, our ability to harness proteolysis for disease treatment will increase with our understanding of protease biology and the molecular mechanisms responsible. New technologies for rationally engineering proteases, as well as improved delivery options, will expand greatly the potential applications of these enzymes. The recognition that proteases are, in fact, an established class of safe and efficacious drugs will stimulate investigation of additional therapeutic applications for these enzymes. Proteases therefore have a bright future as a distinct therapeutic class with diverse clinical applications.

Meta-analysis of studies of patients in the United Arab Emirates with ST-elevation myocardial infarction treated with thrombolytic agents

We performed a meta-analysis of 6 studies we conducted in the United Arab Emirates from 1995 to 2009. These included 1,262 patients with ST-elevation myocardial infarction treated with thrombolytic drugs <6 hours after onset of symptoms and signs of myocardial infarction. All patients were treated with tenecteplase or alteplase to induce coronary thrombolysis. Characteristics of patients in all studies were quite similar. Overall mean age was 47 years, 98% were men, 28% had diabetes, 25% were hypertensive, 20% were hyperlipidemic, 56% were smokers, and 9% had sustained previous myocardial infarction. Incidence of adverse outcomes of 30-day mortality (3%), reinfarction (2.5%), stroke (0.4%), or major bleeding (0%) was low compared to global experience with recanalization regardless of how it was induced. There was no incidence of major bleeding requiring transfusion or laparotomy. In conclusion, in predominantly young men in the United Arab Emirates who were admitted and treated early after onset of an acute ST elevation myocardial infarction, recanalization induced by thrombolysis was an attractive therapeutic approach.

Thrombolytics and myocardial infarction

Coronary artery disease is the single leading cause of death in the United States. Occlusion of the coronary artery was identified to be the cause of myocardial infarction almost a century ago. Following a series of investigations, streptokinase was discovered and demonstrated to be beneficial for the treatment of patients with acute myocardial infarction in terms of reducing short- and long-term mortality. Newer agents including tissue plasminogen activators such as alteplase, reteplase, tenecteplase were developed subsequently. In the present era, thrombolytic therapy and primary percutaneous coronary intervention has revolutionized the way patients with acute myocardial infarction are managed resulting in significant reduction in cardiovascular death. This article provides an overview of the various thrombolytic agents utilized in the management of patients with acute myocardial infarction.

[Bleeding risk in ST-segment elevation myocardial infarction]

Coronary reperfusion of acute coronary syndromes with ST segment elevation requires medical treatment involving potential thrombolysis as well as very potent anticoagulant and antiplatelet medications. In such a therapeutic setting, the risk of bleeding complications may be high and should be taken into account accordingly. An accurate definition of these bleeding complications is crucial in order to compare all currently available treatments and strategies appropriately. The heterogeneous definitions often published in the literature make any valid interpretations of the results very difficult. These bleeding complications, which affect negatively the outcome of patients undergoing treatment should be adequately anticipated in our treatment strategies. An exhaustive knowledge of the bleeding risk factors is necessary in order to adjust the treatment modalities. The occurrence of bleeding may be related to the vascular approach used for cardiac catheterization. In this respect, the superiority of the radial approach has been widely demonstrated. In addition, certain instances of bleeding are not related to the vascular approach, such as digestive and neurological bleeding which can have very severe consequences. Consequently, it is necessary to adapt treatments with heterogeneous potential for bleeding to individual bleeding risk factors, which may be quantified by scores measuring the bleeding risk. Finally, treatment combinations must often be carefully tailored to the characteristics of each individual patient.

Optimizing the use of thrombolytics in ST-segment elevation myocardial infarction

The advent of thrombolytic therapy was a major advance in the treatment of ST-segment elevation myocardial infarction (STEMI). The administration of fibrinolytic reperfusion therapy can reduce mortality rates by as much as 30%, with the greatest benefit observed if therapy is administered soon after symptom onset. Outcomes with thrombolytic therapy are improved if there is adjunctive treatment with aspirin, clopidogrel and an anti-thrombin agent. Although there is evidence that primary percutaneous coronary intervention (PCI) is the most effective reperfusion strategy, the majority of hospitals still do not have PCI capabilities and, thus, thrombolytic therapy remains a cornerstone of treatment for STEMI. Trials of thrombolytic therapy have demonstrated that initial patency rates can approach 85%, but there is still a need for improvement of non-invasive markers that predict failure or re-occlusion of the infarct-related artery. Because of the overwhelming data demonstrating the importance of rapid reperfusion, current studies are examining the role of earlier treatment of patients with STEMI via pre-hospital administration and/or coordinated systems for rapid diagnosis, transfer and delivery of definitive care. Facilitated PCI, a strategy of thrombolytic therapy followed by immediate PCI, has not been shown to be beneficial and current studies are examining the optimal timing of coronary angiography after thrombolytic therapy.

Review of tenecteplase (TNKase) in the treatment of acute myocardial infarction

TNKase is a genetically engineered variant of the alteplase molecule. Three different mutations result in an increase of the plasma half-life, of the resistance to plasminogen-activator inhibitor 1 and of the thrombolytic potency against platelet-rich thrombi. Among available agents in clinical practice, TNKase is the most fibrin-specific molecule and can be delivered as a single bolus intravenous injection. Several large-scale clinical trials have enrolled more than 27,000 patients with acute myocardial infarction, making the use of this drug truly evidence-based. TNKase is equivalent to front-loaded alteplase in terms of mortality and is the only bolus thrombolytic drug for which this equivalence has been formally demonstrated. TNKase appears more potent than alteplase when symptoms duration lasts more than 4 hours. Also, TNKase significantly reduces the rate of major bleeds and the need for blood transfusions. The efficacy of TNKase may be further improved by enoxaparin substitution for unfractionated heparin, provided that enoxaparin dose adjustment is made for patients more than 75 years old. Hitherto, the small available randomized studies and international clinical registries suggest that pre-hospital TNKase is as effective as primary angioplasty, thus laying the foundations for a new fibrinolytic, TNKase-based strategy as the backbone of reperfusion in acute myocardial infarction.

C-terminal provasopressin (copeptin) is associated with left ventricular dysfunction, remodeling, and clinical heart failure in survivors of myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) is associated with left ventricular (LV) dysfunction and clinical heart failure. Arginine vasopressin is elevated in heart failure and the C-terminal of provasopressin (Copeptin) is associated with adverse outcome post-AMI. The aim of this study was to describe the association between Copeptin with LV dysfunction, volumes, and remodeling and clinical heart failure post-AMI.

METHODS AND RESULTS

We studied 274 subjects with AMI. Copeptin was measured from plasma at discharge and subjects underwent echocardiography at discharge and follow-up (median 155 days). Subjects were followed for clinical heart failure for a median of 381 days. Remodeling was assessed as the change (Delta) in LV volumes between echo examinations. Copeptin correlated directly with wall motion index score (WMIS) and inversely with LV ejection fraction (LVEF) at discharge (WMIS, r=0.276, P < .001; LVEF, r=-0.188, P=.03) and follow-up (WMIS, r=0.244, P < .001; LVEF, r=-0.270, P < .001) and with ventricular volumes at follow-up (LVEDV, r=0.215, P=.002; LVESV, r=0.299, P < .001). Copeptin was associated with ventricular remodeling; DeltaEDV; r=0.171, P=0.015, DeltaESV; r=0.186, P=.008. Subjects with increasing LVESV had higher levels of Copeptin (median 6.30 vs. 5.75 pmol/L, P=.012). Subjects with clinical heart failure (n=30) during follow-up had higher Copeptin before discharge (median 13.55 vs. 5.80, P < .001). In a Cox proportional hazards model, Copeptin retained association with clinical heart failure. Kaplan-Meier assessment revealed increased risk in subjects with Copeptin >6.31 pmol/L.

CONCLUSIONS

Copeptin is associated with LV dysfunction, volumes, and remodeling and clinical heart failure post-AMI. Measurement of Copeptin may provide prognostic information and the AVP system may be a therapeutic target in post-MI LV dysfunction.

Design and implementation of resuscitation research: special challenges and potential solutions

Evaluation of the effectiveness of resuscitation interventions is challenging. We describe these challenges, which include design, enrolment and analysis issues. Randomized trials establish if interventions work in predefined populations. "Efficacy" trials determine whether interventions work under ideal conditions. "Effectiveness" trials determine whether interventions work under usual practice conditions. These trials represent a trade-off between internal validity versus external validity. Randomized trials use random allocation of participants to interventions to produce study groups that are similar with respect to known and unknown risk factors, reduce bias in the allocation of participants, and assure that statistical tests have valid significance levels. In the emergency setting, there is a risk that treatment offered to control patients will be contaminated by providers' experiences of applying the intervention to patients receiving the experimental intervention. Frequently there is not time to obtain consent from a patient in an emergency setting. Exception from consent can be applied if certain conditions are met. Enrolment in a research study must be initiated quickly in an emergency setting or the patient will die or become disabled. In any trial, data can be used to explore different aspects of response to treatment: multiple treatments, subgroups, events; and interim analyses. We propose solutions to these challenges to help potential investigators through the myriad of difficulties in initiating trials in a complex environment. Design of simple trials that have adequate power enhances their external validity. Allocating groups of episodes to interventions by randomizing by clusters, rather than by individual patients reduces provider noncompliance. Waiver from consent for emergency research and use of novel technologies could facilitate enrolment despite time constraints. Rigorous statistical methods can be used to analyze multiple data without an excessive increase in the chance of a false-positive result.

Investigation of the safety of tenecteplase to the outer retina

PURPOSE

To investigate the safety of the thrombolytic agent, tenecteplase to the outer retina in pig eyes.

METHODS

Tenecteplase (50 microg) was injected into the subretinal space in one eye while the fellow eye received balanced salt solution. At 24 h, 1 week and 9 weeks the eyes were examined by indirect ophthalmoscopy and photographed. Animals were killed at 9 weeks, eyes enucleated and processed for light and transmission electron microscopy. Three locations within the area of the injection bleb were analysed.

RESULTS

Retinal pigment epithelial defects, which appeared to be iatrogenic and confined to the injection site, were seen in most of the treated and control eyes. There was no significant difference in the degree of retinal damage between the two groups of eyes at the three sites examined (P > 0.05).

CONCLUSION

Fifty micrograms of tenecteplase appears to be a safe dose with no evidence of toxicity to the outer retina and may have a potential role in the treatment of submacular haemorrhage.

Early management of ST-segment elevation myocardial infarction

Improvements in the management of ST-segment elevation myocardial infarction(STEMI) have led to a reduction in the acute and long-term mortality rates. The first important decision in the care of patients who have STEMI is the method of reperfusion. Whether percutaneous intervention (PCI) or fibrinolytic therapy is chosen depends on a number of factors. This article reviews the data on PCI and fibrinolytics in the context of consensus guidelines, outlines adjunctive medical therapies important in the first 24 hours, and discusses a strategy for making the decisions and a hypothetical construct for evaluating new drugs and procedures in the future.

Medical Error Prevention in ED Triage for ACS: Use of Cardiac Care Decision Support and Quality Improvement Feedback

Medical errors in the care of patients who present with acute coronary syndrome (ACS)include errors in emergency department (ED) triage, such as the decision to send home a patient who presents with ACS or to hospitalize a patient who does not have ACS to the cardiac care unit (CCU), and errors in treatment, such as the failure to promptly use reperfusion therapy for patients who present with ST-elevation acute myocardial infarction(AMI). ECG-based acute cardiac ischemia time-insensitive predictive instrument(ACI-TIPI) and thrombolytic predictive instruments (TPIs), with a linked TIPI information system (TIPI-IS), provide real-time, concurrent, and retrospective decision support tools and feedback for the prevention of medical errors in the care of patients who present with ACS. In real-time, ACI-TIPI probabilities printed on the ECG header for the ED physician, provide an additional piece of information for triage decision making, and the ACI-TIPI Risk Management form reduces liability risk by prompting consideration and documentation of key clinical factors in the diagnosis of ACI. Also in real-time, the TPI increases overall coronary reperfusion therapy use. Concurrent flagging by TIPI-IS uses electronically acquired ECG and hospital data to provide concurrent alerts about potential misdiagnosis or mis-triage of patients with ACS. Retrospectively TIPI-IS-based feedback reports allow performance improvement. These examples of information technology tools integrated into ECG equipment already used in hospitals to deliver patient care demonstrate the potential to adapt other existing equipment or other patient care activities to enhance patient safety and error reduction.

International Resuscitation Network Registry: design, rationale and preliminary results

There is a lack of high-quality information about the effectiveness of resuscitation interventions and international differences in structure, process and outcome after out-of-hospital cardiac arrest and cardiopulmonary resuscitation because data are not collected uniformly. An internet-based international registry could make such evaluations possible, and enable the conduct of large randomized controlled trials of resuscitation therapies. A prospective international cohort study was performed that included 571 infants, children and adults (a) who experienced cardiac arrest requiring chest compressions or external defibrillation, (b) outside the hospital in the study communities and (c) upon whom resuscitation was attempted by EMS personnel. Cardiac arrest was defined as lack of responsiveness, breathing or movement in individuals for whom the EMS system is activated for whom an arrest record is completed. All data were collated via a secure and confidential web-based method by using automated forms processing software with appropriate variable range checks, logic checks and skip rules. Median number of missing responses for each variable was 0 (interquartile range 0, 0). Twenty-seven percent of the patients had a first recorded rhythm of ventricular fibrillation or ventricular tachycardia, 60% had a witnessed arrest, and 34% received bystander CPR. Mean time from call to arrival on scene was 7.1+/-5.1 min. Six percent of the patients survived to hospital discharge. The resuscitation process was highly variable across centers, and survival and neurological outcome were also significantly and independently different across centers. This study shows that it is possible to collect data prospectively describing the structure, process and outcome associated with cardiac arrest in multiple international sites via the internet. Therefore, it is feasible to conduct adequately powered randomized trials of resuscitation therapies in international settings.

Thrombolytic Therapy: Current Clinical Practice

Thrombolytic therapy is an essential tool in the array of therapies designed to reopen arteries and veins occluded with thrombus. As the use of thrombolytic agents has entered mainstream practice, their application has expanded to include a wide variety of indications and settings. Thrombolytic agents are used in patients who have thrombosis of coronary arteries, precerebral and cerebral arteries, the aorta, iliac and mesenteric arteries, and peripheral arteries. The use of thrombolysis in venous thrombosis has included deep venous thrombosis of the upper and lower extremities and vena cava, mesenteric veins, cerebral veins, and central access catheters. Guidelines are available from the American College of Cardiology/American Heart Association regarding thrombolysis in myocardial infarction and from the American Stroke Association regarding thrombolysis in acute ischemic stroke.

Errors in weight estimation in the emergency department: Comparing performance by providers and patients

To examine biases in weight estimation by Emergency Department (ED) providers and patients, a convenience sample of ED providers (faculty, residents, interns, nurses, medical students, paramedics) and patients was studied. Providers (n = 33), blinded to study hypothesis and patient data, estimated their own weight as well as the weight of 11-20 patients each. An independent sample of patients (n = 95) was used to assess biases in patients' estimation of their own weight. Data are represented as over, under, or within +/- 5 kg, the dose tolerance standard for thrombolytics. Logistic regression analysis revealed that patients are almost nine times more likely to accurately estimate their own weight than providers; yet 22% of patients were unable to estimate their own weight within 5 kg. Of all providers, paramedics were significantly worse estimators of patient weight than other providers. Providers were no better at guessing their own weight than were patients. Though there was no systematic estimate bias by weight, experience level (except paramedic), or gender for providers, those providers under 30 years of age were significantly better estimators of patient weight than older providers. Although patient gender did not create a bias in provider estimation accuracy, providers were more likely to underestimate women's weights than men's. In conclusion, patient self-estimates of weight are significantly better than estimates by providers. Inaccurate estimates by both groups could potentially contribute to medication dosing errors in the ED.

Thrombolysis and Adjunctive Therapy in Acute Myocardial Infarction

This chapter about antithrombotic therapy for acute myocardial infarction (MI) is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients with ischemic symptoms characteristic of acute MI of < 12 h in duration, and ST-segment elevation or left bundle-branch block (of unknown duration) on the ECG, we recommend administration of any approved fibrinolytic agent (Grade 1A). We recommend the use of streptokinase, anistreplase, alteplase, reteplase, or tenecteplase over placebo (all Grade 1A). For patients with symptom duration < 6 h, we recommend the administration of alteplase over streptokinase (Grade 1A). For patients with known allergy or sensitivity to streptokinase, we recommend alteplase, reteplase, or tenecteplase (Grade 1A). For patients with acute posterior MI of < 12 h duration, we suggest fibrinolytic therapy (Grade 2C). In patients with any history of intracranial hemorrhage, closed head trauma, or ischemic stroke within past 3 months, we recommend against administration of fibrinolytic therapy (Grade 1C+). For patients with acute ST-segment elevation MI whether or not they receive fibrinolytic therapy, we recommend aspirin, 160 to 325 mg p.o., at initial evaluation by health-care personnel followed by indefinite therapy, 75 to 162 mg/d p.o. (both Grade 1A). In patients allergic to aspirin, we suggest use of clopidogrel as an alternative therapy to aspirin (Grade 2C). For patients receiving streptokinase, we suggest administration of either i.v. unfractionated heparin (UFH) [Grade 2C] or subcutaneous UFH (Grade 2A). For all patients at high risk of systemic or venous thromboembolism (anterior MI, pump failure, previous embolus, atrial fibrillation, or left ventricular thrombus), we recommend administration of IV UFH while receiving streptokinase (Grade 1C+).

Can the time window for administration of thrombolytics in stroke be increased?

Level 1 evidence now shows that thrombolysis in cases of acute ischaemic stroke is effective if administered within 3 hours of stroke onset. This benefit has been shown to be time dependent and potentially extends beyond 3 hours, with evidence that potentially viable penumbral tissue may be present in a significant proportion of cases well beyond 3-6 hours and, in isolated cases, perhaps up to 48 hours. This exposes a "stroke recovery gap", the difference observed between the clinical response to thrombolytic therapy in a given population of patients presenting with ischaemic stroke and the potential clinical recovery if all of the penumbra were salvaged under ideal circumstances. The means of bridging this "stroke recovery gap" using thrombolysis must involve extending the therapeutic time window (i.e. the time between stroke onset and administration of thrombolytics). Approaches to do this include the use of: (i) improved patient selection with modern neuroimaging techniques, particularly magnetic resonance imaging using perfusion-weighted image/diffusion-weighted image mismatch; (ii) newer thrombolytic agents; (iii) lower doses of these agents; (iv) varied methods of administration of thrombolytic therapy including combined intravenous and intra-arterial approaches; and (v) adjunctive therapies such as neuroprotectants. Should these means of extending the time window for thrombolysis prove successful, a more widespread use of this form of acute stroke therapy will be possible.

Pharmacokinetics and pharmacodynamics of tenecteplase in fibrinolytic therapy of acute myocardial infarction

Tenecteplase is a novel fibrinolytic protein bioengineered from human tissue plasminogen activator (alteplase) for the therapy of acute ST-segment elevation myocardial infarction. Specific mutations at three sites in the alteplase molecule result in 15-fold higher fibrin specificity, 80-fold reduced binding affinity to the physiological plasminogen activator inhibitor PAI-1 and 6-fold prolonged plasma half-life (22 vs 3.5 minutes). Consequently, tenecteplase can be administered as a single intravenous bolus of 30-50mg (0.53 mg/kg bodyweight) over 5-10 seconds, in contrast to the 90-minute accelerated infusion regimen of alteplase. Tenecteplase plasma concentration-time profiles have been obtained from a total of 179 patients with acute myocardial infarction. Tenecteplase exhibited biphasic disposition; the initial disposition phase was predominant with a mean half-life of 17-24 minutes, and the mean terminal half-life was 65-132 min. Over the clinically relevant dose range of 30-50mg, mean clearance (CL) was 105 ml/min. The mean initial volume of distribution V(1) was 4.2-6.3L, approximating plasma volume, and volume of distribution at steady state was 6.1-9.9L, suggesting limited extravascular distribution or binding. Bodyweight and age were found to influence significantly both CL and V(1). Total bodyweight explained 19% of the variability in CL and 11% of the variability in V(1), and a 10kg increase in total bodyweight resulted in a 9.6 ml/min increase in CL. This relationship aided the development of a rationale for the weight-adjusted dose regimen for tenecteplase. Age explained only a further 11% of the variability in CL. The percentage of patients who achieved normal coronary blood flow was clearly related to AUC. More than 75% of patients achieved normal flow at 90 minutes after administration when their partial AUC(2-90) exceeded 320 microg.min/ml, corresponding to an average plasma concentration of 3.6 microg/ml. Systemic exposure to tenecteplase at all times after bolus administration of 30-50mg was higher than for alteplase 100mg. Tenecteplase has demonstrated equivalent efficacy and improved safety compared with the current gold standard alteplase in a large mortality trial (ASSENT-2). This suggests that the reduced clearance, greater fibrin specificity and higher PAI-1 resistance of tenecteplase allow higher plasma concentrations and thus a more rapid restoration of coronary patency to be attained, while providing a reduction in major non-cerebral bleeding events.

Comparative fibrinolytic activity of front-loaded alteplase and the single-bolus mutants tenecteplase and lanoteplase during treatment of acute myocardial infarction

BACKGROUND

Quantification of fibrinolytic activity (FAct) in clinical practice has been abandoned because of the complexity of existing assays. The relationship between thrombolytic drug concentration and FAct is complex. FAct profiles of currently used thrombolytic drugs were not characterized.

METHODS

By use of a system that quantifies FAct by shortening of clot lysis onset time (LOT), we measured LOT in vitro with incremented concentrations of alteplase (t-PA) and tenecteplase (TNK-tPA) and ex vivo in patients with acute myocardial infarction who were receiving front-loaded t-PA (n = 31), 30 to 40 mg TNK-tPA (n = 19), and 120 kU/kg lanoteplase ([n-PA] n = 23).

RESULTS

In vitro, FAct depended on drug concentration by means of a double exponential model revealing 2 distinct activity zones (weak/strong). Ex vivo, no FAct was detected before agent administration (LOT > 1200 seconds). Ten minutes after a bolus was given, FAct was sharply increased in all patients, but it increased more with TNK-tPA than with t-PA or n-PA (mean LOT of 109, 125, and 130 seconds, respectively, P <.05). At 90 minutes, accelerated infusion of t-PA resulted in FAct that remained stronger than that observed for TNK-tPA (P <.0001) or n-PA (P =.011). At 180-minutes, significant FAct (LOT <600 seconds) was only observed in patients who received n-PA.

CONCLUSION

This study provides the first direct comparison of FAct between t-PA, TNK-tPA, and n-PA by use of the LOT test, the results of which are reliably related to drug concentration. The ideal FAct profile would combine an immediate strong FAct of relatively short duration, as seen with TNK-tPA, that may contribute to its better efficacy/safety profile in the Assessment of Safety and Efficacy of a New Thrombolytic Agent-2 (ASSENT-2) trial. Prolonged FAct after n-PA may contribute to increased hemorrhagic complications, as seen in the Intravenous n-PA for Treatment of Infarcting Myocardium Early-2 (InTIME-2) trial. Thus, characterizing FAct profiles might provide insights in developing more efficient thrombolytic regimens.

Thrombolytic therapy: clinical applications

The therapeutic use of thrombolytic agents is the result of the increasing understanding of the pathophysiologic mechanisms underlying normal and deranged thrombosis and fibrinolysis. Plasminogen activators capable of increasing the production of plasmin exhibit considerable efficacy in the treatment of a variety of arterial and venous thrombotic disorders. The ideal thrombolytic agent has not been developed, but the desired clinical result of rapid opening of the thrombosed vessel without reocclusion, without activation of systemic fibrinogenolysis, and without a risk of hemorrhage are defined. Clinical studies clearly demonstrate that the addition of a variety of adjunctive agents to available thrombolytics enhances benefit without inordinate risk. The addition of intravascular angioplasty and stenting to thrombolysis increases the potential long-term benefit. Newer thrombolytic agents and new protocols for the use of existing therapies offer the promise of saving many who would otherwise succumb to coronary or cerebral arterial thrombosis or to venous thromboembolism.