Selection of Patients with Acute Myocardial Infarction for Thrombolytic Therapy

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Abstract
To critically review the current recommendations regarding the eligibility of patients with myocardial infarction for thrombolytic therapy. Relevant studies published from January 1980 to January 1990 were identified through a computerized search of the English-language literature using MEDLINE and by a manual search of the bibliographies of all identified articles. All randomized, controlled trials of intravenous thrombolysis in acute myocardial infarction and unstable angina were reviewed. Smaller, observational studies and previous review articles were included when relevant to the discussion. Key data were extracted from each article, including the proportions of patients eligible for thrombolysis, the reasons for exclusion from thrombolytic therapy, and the clinical outcomes of patients treated and of those excluded from treatment. The validity of certain exclusion criteria was examined using subgroup analysis from the large, randomized mortality trials of intravenous thrombolysis and observations from smaller, nonrandomized studies. To date, relatively few patients with myocardial infarction have been considered eligible for fibrinolytic therapy. In this group, both early and late mortality have been significantly reduced. Patients excluded from thrombolysis, however, continue to have a high early mortality. The data suggest that the potential benefits of this treatment might be extended to selected high-risk subgroups. In particular, the risk-benefit ratio may favor the inclusion of otherwise healthy elderly patients; certain patients presenting more than 6 hours after the onset of symptoms; and patients with a history of controlled systolic hypertension or brief, nontraumatic cardiopulmonary resuscitation. The data do not support the use of fibrinoytic therapy as primary treatment in patients with unstable angina or suspected myocardial infarction in the absence of confirmatory electrocardiographic changes. The full potential of thrombolytic therapy to alter the natural history of acute myocardial infarction can only be realized through the continued evalation of selection criteria and the identification and treatment of the greatest possible number of eligible patients.