Thrombolysis after myocardial infarction

Thrombolytic Therapy in Acute Myocardial Infarction: A Review with Current Recommendations

Thrombolytic therapy has clearly become an established therapeutic modality to treat patients with acute myocardial infarction. Since there is no ideal agent at this time, we must evaluate the advantages and disadvantages of current therapy based on major clinical studies. Thrombolysis is the body's natural response to dissolving clots after they have served their purpose. Thrombolytic agents accelerate fibrinolysis by overwhelming the system. There are 4 thrombolytic agents currently available: streptokinase urokinase, anistreplase (APSAC), and rt-PA. Tissue plasminogen activator is a naturally occurring protein that can be created with genetic recombinant technology (rt-PA). It establishes higher patency rates (70–90%) than the other available thrombolytic agents. Recently published results of accelerated rt-PA infusion during acute myocardial infarction demonstrate that the infarct-related artery seems to open more quickly and provide greater blood flow. The use of intravenous heparin as adjunctive therapy along with aspirin seems to maintain patency at comparable levels to streptokinase. Not only is mortality reduced in the accelerated rt-PA group, but complications from myocardial infarction such as arrhythmia and heart failure are significantly reduced. rt-PA remains the drug of choice in the hypotensive patient and, because of potential allergy, in patients with previous exposure to streptokinase. Percutaneous transluminal coronary angioplasty is frequently needed to improve long-term patency and reduce ischemic episodes. Recent studies show that it may provide some advantage over thrombolytic therapy, because the artery can be opened faster, with higher flow rates.

Lessons from the European Cooperative recombinant tissue-type plasminogen activator (rt-PA) versus placebo trial

A new European Cooperative Study Group trial of 721 patients has recently found recombinant tissue-type plasminogen activator (rt-PA) to positively affect infarct size, left ventricular function, cardiovascular morbidity and early survival. In this 26 center trial, patients were randomized to receive either placebo or 100 mg rt-PA intravenously over 3 h. Heparin (5,000 U bolus injection and then 1,000 U/h) and aspirin (250 mg initially, then 75 to 125 mg every other day) were given to all patients until angiography was performed (10 to 22 days after allocation). Enzymatic infarct size was found to be 20% smaller in the rt-PA group (2p = 0.0018) than in the control group. At angiography, 83% of rt-PA-treated patients had a patent infarct-related vessel compared with 77% of the placebo-treated patients. Ejection fraction was 2.2% points higher (2p = 0.04) and end-diastolic and end-systolic volumes were +/- 6 ml smaller (2p = 0.003) than in the control group, indicating an improved left ventricular pump function in the thrombolysis group. Cardiovascular complications such as shock, ventricular fibrillation and pericarditis were markedly fewer in patients treated with rt-PA, but bleeding complications occurred more frequently. An intracranial hemorrhage within 3 days after the infusion of rt-PA was observed in five patients (1.4%). None of these bleeding episodes was causally related to death. Although this European Cooperative trial was not designed primarily as a mortality study, important reductions in early mortality rates were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombolytic reperfusion of acute myocardial infarction: resolved and unresolved issues

Intensive clinical investigation has led to the acceptance of many fundamental aspects of reperfusion therapy, especially its salutary effects on improved survival, left ventricular function and reduced infarct size. However, many unresolved issues are currently being addressed or will be the focus of future clinical trials. These include patient selection with respect to risk profile and time of presentation, the choice of a thrombolytic agent, the role of adjunctive therapies and the optimal use and timing of follow-up coronary revascularization procedures. The rapidly evolving status of myocardial reperfusion therapy is reviewed, with specific attention to these important yet unresolved aspects.