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Heart attack patients are commonly treated with thrombolytic medications such as tissue plasminogen activator (tPA) and streptokinase to break up and prevent blood clots that could worsen their condition. The more potent tPA costs roughly $2,000 more per dose than streptokinase in the United States and has not been universally adopted. However, for selected heart attack patients, use of tPA yields substantially better outcomes than streptokinase, and use of the less expensive agent is difficult to justify, concludes a study supported in part by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00070 and HS08212).
Researchers led by Harry P. Selker, M.D., M.S.P.H., and Joni R. Beshansky, R.N., M.P.H., of Tufts University School of Medicine, developed a mathematical model to select patients likely to benefit from tPA compared with streptokinase based on a computerized electrocardiogram-based instrument, which uses clinical and electrocardiographic variables to predict outcomes in heart attack patients with and without thrombolytic therapy. They used this model to predict the benefits of tPA therapy in 24,146 patients with occluded coronary arteries and compared these predictions with the actual benefits of tPA, after classifying patients by their risks of death and intracranial hemorrhage.
Their model, confirmed by patient outcomes, predicted that among heart attack patients, 61 percent of the benefit of tPA use in reducing mortality accrued to only 25 percent of patients (who gained a 2 percent mortality benefit). Treating half of all patients could capture 85 percent of the benefit but not when the risk of intracranial hemorrhage was included in the model. Targeting tPA to just the highest benefit half would save more than $100 million and more than 300 lives. Patients most likely to benefit from tPA were older, more frequently had anterior wall infarcts, had lower systolic blood pressure, and were treated sooner after the onset of symptoms than low-benefit patients.
For more information, see "An independently derived and validated predictive model for selecting patients with myocardial infarction who are likely to benefit from tissue plasminogen activator compared with streptokinase," by David M. Kent, M.D., M.S., Rodney A. Hayward, M.D., John L. Griffith, Ph.D., and others, in the August 1, 2002, American Journal of Medicine 113, pp. 104-11.
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