Trickle down thrombolysis

Plasminogen activator inhibitor type-1 (part two): role for failure of thrombolytic therapy. PAI-1 resistance as a potential benefit for new fibrinolytic agents

Rapid and sustained reperfusion of an occluded coronary artery is the goal of thrombolytic therapy in acute myocardial infarction. However, the clot-dissolving efficacy of fibrinolytic agents such as tissue-type plasminogen activator (t-PA) is limited, in vivo, in part by the action of plasminogen activator inhibitor type-1 (PAI-1). A new generation of fibrinolytic agents has been genetically engineered to have greater resistance to PAI-1 inhibition. This article reviews the pathophysiologic role of PAI-1 in failure of thrombolytic therapy and describes the advantages that PAI-1-resistance may confer upon fibrinolytic agents such as TNK-t-PA, the new fibrinolytic agent with the most powerful PAI-1 resistance.

Thrombolytic therapy in acute myocardial infarction

Early reperfusion of thrombotically occluded coronary arteries by thrombolytic therapy has become a routine option in initial therapy of acute myocardial infarction. Many efforts have been made to improve the biological properties of thrombolytic agents in terms of fibrin specificity, plasma half-life and resistance to natural plasma inhibitors, to improve adjuvant therapy and to shorten the 'pain to reperfusion' time. Numerous randomised, multicentre trials have analysed the benefit of the various thrombolytic agents and regimens, which has enabled the creation of a 'current standard of therapy'. This review presents an update on available thrombolytic agents, their biochemical and pharmacological properties and results from clinical trials.

Corrected TIMI frame count does not predict 30-day adverse outcomes after reperfusion therapy for acute myocardial infarction

BACKGROUND

Thrombolysis in Myocardial Infarction (TIMI) flow grading is limited by subjectivity and imprecision. The corrected TIMI frame count (cTFC) has been proposed to obviate these problems. We sought to validate the utility of the cTFC in predicting adverse clinical outcomes after reperfusion therapy.

METHODS AND RESULTS

We used angiographic core laboratory data from the Intravenous nPA for Treating Infarcting Myocardium Early Study (lanoteplase versus alteplase) to assess the predictive capacity of both final TIMI flow and cTFC on 30 day-composite adverse outcome (death, reinfarction, and new or worsening congestive heart failure). Only 390 angiograms of 586 were analyzable for cTFC; 33.4% of angiograms could not be analyzed for cTFC because filling of distal landmarks was not visualized for technical reasons such as inadequate panning. The interobserver correlation for determination of the cTFC was 0.99 and the intraobserver correlation was 0.97. The cTFC in the group with adverse outcomes was 49 +/- 34; in the group without adverse outcomes, it was 44 +/- 31 (P =.27). Of note, the TIMI flow correlated with adverse outcome in the overall group of patients (P =.018, area under the receiver-operator characteristic curve [c] = 0. 590) as well as in the group of patients with cines analyzable for cTFC (P =.025, c = 0.600). The independent correlates of adverse outcomes were age (P <.001), heart rate (P =.001), TIMI flow grade (P =.027), and infarct location (P =.038) but not cTFC.

CONCLUSIONS

The cTFC did not predict adverse outcomes in this population of patients but did show excellent reproducibility within our core laboratory.

Thrombolytic therapy versus primary angioplasty in the treatment of acute myocardial infarction

The quest to identify the acute interventional approach that will achieve the lowest mortality rate with the fewest adverse events has led to a continued controversy surrounding the relative merits of thrombolytic therapy compared with primary angioplasty in the setting of acute myocardial infarction. This article summarizes the benefits and limitations of each reperfusion strategy and highlights adjunctive therapies that will enhance either treatment strategy.

Early noninvasive identification of failed reperfusion after intravenous thrombolytic therapy in acute myocardial infarction

OBJECTIVES

This study sought to evaluate a biochemical approach to the early noninvasive assessment of reperfusion.

BACKGROUND

In patients with an acute myocardial infarction, a rapid noninvasive method of detecting failure of intravenous thrombolytic therapy to restore early Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow in the infarct-related artery (IRA) is needed.

METHODS

Serial blood samples were collected to assay creatine kinase-MB fraction (CKMB mass), cardiac troponin T and myoglobin concentrations in 105 patients with a myocardial infarction who underwent early angiography after intravenous streptokinase. The ratios of the 60- and 90-min concentrations to prethrombolytic values were used to determine an index that could identify failure to achieve TIMI grade 3 flow in the IRA at 90 min.

RESULTS

Significant increases in serum concentrations of markers at 60 min were more likely with TIMI grade 3 flow (59 patients) than with TIMI grade 0 to 2 flow (46 patients). Ratios < or = 5 at 60 min after thrombolysis detected failure to achieve 90-min TIMI grade 3 flow with 92% to 97% sensitivity, 43% to 60% specificity and 63% to 76% positive and 86% to 94% negative predictive values. Ratios < or = 10 at 90 min showed 88% to 95% sensitivity, 49% to 65% specificity and 61% to 69% positive and 86% to 94% negative predictive values for TIMI flow grade < 3. The overall predictive values were thus similar for all three markers.

CONCLUSIONS

In acute myocardial infarction treated with intravenous streptokinase, a simple measurement of increased serum concentrations of CKMB mass, cardiac troponin T or myoglobin at 60 and 90 min can accurately predict failure to achieve TIMI grade 3 flow in the IRA at 90 min.

Acute myocardial infarction: enhancing the results of reperfusion therapy

Reperfusion therapy (by either administration of thrombolytic agents or immediate angioplasty) is the mainstay of treatment of acute myocardial infarction, yet it remains underutilized. Additionally, many patients do not experience optimal reperfusion because of suboptimal flow rate in the infarct-related artery, abnormal microvascular flow, and intermittent or complete reocclusion of the infarct-related artery. Strategies to enhance the results of reperfusion therapy include expanding the population of patients considered as candidates, earlier treatment, newer methods to improve infarct-related artery flow rates, and ancillary treatments currently being studied to reduce reperfusion injury, which may be one cause of decreased microvascular flow. Although aspirin, heparin, and warfarin sodium have been the conventionally used agents for inhibiting thrombin and platelet function, newer agents such as hirudin and inhibitors of the platelet glycoprotein IIb-IIIa receptor are becoming available, and their clinical application will increase in the future.

Timing, mode, and predictors of death after direct angioplasty for acute myocardial infarction

The timing and mechanisms of early (30 day) mortality in 330 consecutive patients treated with direct angioplasty less than 12 hr after onset of myocardial infarction without antecedent thrombolysis were studied. There were 38 deaths (11.5% of pts), with a majority being due to cardiogenic shock (76%). Other causes included acute closure (11%), death after emergency bypass surgery (5%), ventricular arrhythmias (5%), and respiratory failure (3%). No deaths from stroke or cardiac rupture were seen, in contrast to trials of thrombolytic agents. Most deaths were seen early, with 47% occurring within 1 day, 35% from days 2-7, and 18% from days 8-30. Death from cardiogenic shock was the most common cause of death throughout this period: 83% of deaths in days 0-3, 88% of deaths in days 4-6, and 43% of deaths in days 8-30. Significant predictors of early death included older age (P < .0001), multi-vessel disease (P < .05), direct angioplasty failure (P < .05), reduced ejection fraction (P < .0001), and anterior myocardial infarction (P < .0005). Gender, prior myocardial infarction, and prior bypass surgery did not affect mortality. Cardiogenic shock is the most common cause of early death after direct angioplasty for myocardial infarction. Patients with one or more risk factors for early death may benefit from additional myocardial salvage or revascularization efforts in the early post-infarct period. Certain causes of death after direct angioplasty (cardiac, rupture, stroke) appear to be less common than data reported for lytic therapy for myocardial infarction.