Fibrinolytic therapy for acute ST-segment elevation myocardial infarction

Anthony Kerigan's thoughtful letter provides me a welcome opportunity to expand on the important issue of fibrinolytic therapy in the elderly. Although the evidence for fibrinolysis in patients older than 75 years is somewhat less strong than that for younger patients (on the basis of numbers of patients treated), it remains, in my view, convincing.¹ The retrospective administrative data reported by Thiemann and colleagues have significant deficiencies, including exclusion of patients with left bundle branch block and patients who were treated in hospitals with on-site angioplasty capability.² A more recent and more comprehensive study from the Swedish Register of Cardiac Intensive Care included every patient admitted to the coronary care unit at 58 participating hospitals and involved 5428 patients more than 75 years of age with acute myocardial infarction who were admitted with ST-segment elevation or left bundle branch block; this study revealed that the combined end point of cerebral bleeding plus death from any cause at 1 year was significantly lower in the group treated with reperfusion (38.3%) than in the conservatively treated group (48.4%; p < 0.001).³

It is important to emphasize that the risk to life of myocardial infarction in patients over 75 years is much greater than in younger patients; the risk of intracranial hemorrhage is also significantly increased in this population and approximately two-thirds of these intracranial hemorrhages are fatal. Thus, the majority of intracranial hemorrhages are accounted for in the mortality statistics reported. Although this attenuates the relative benefit, it still demonstrates the substantial number of lives per 100 patients treated that can be saved with effective reperfusion therapy.

With respect to the case presented, it is important to recognize that not all inferior myocardial infarctions are the same.⁴ Hence, the elderly woman of low body weight with a tachycardia and congestive heart failure presenting within 4 hours with a clear inferior injury pattern (after resuscitation from a ventricular fibrillation arrest) has a much higher risk of mortality than a patient with an average inferior myocardial infarction of the type reported in the Fibrinolytic Therapy Trialists' overview, i.e., at least 17.4% on the basis of a simple risk index calculation derived from the InTIME II substudy.⁵ Thus, the benefits in this case clearly outweigh the risks.