RISK-BENEFIT ANALYSIS OF THROMBOLYTIC THERAPY FOR ACUTE MYOCARDIAL-INFARCTION - A PERSPECTIVE

Background: The author's purpose is to develop a definition of benefit-risk ratio that may be applied to the use of thrombolytic therapy for suspected acute myocardial infarction. Methods: The predictive value of the presenting ECG for the final diagnosis of acute myocardial infarction was determined from 201 consecutive patients with suspected myocardial infarction. These predictive values for various presenting abnormalities of the ECG were then applied to the Second International Study of Infarct Survival (ISIS-2) data. The assumption was made that deaths in ISIS-2 occurred only in patients with confirmed infarction; the risk of hemorrhagic stroke was taken as 0.5%. The mortality benefit-risk ratio was defined as the number of lives saved by thrombolytic therapy in patients with myocardial infarction (less those with hemorrhagic stroke), to the number of strokes caused by cerebral hemorrhage in those without myocardial infarction. Results: For all patients in ISIS-2, the estimated mortality benefit-risk ratio is 18:1, ranging from 146:1 for patients with both anterior and inferior ST elevation, to 4:1 for those with a normal ECG, and -5:1 for those with ST depression. Overall, 448 patients without cerebral hemorrhage in ISIS-2 benefited from having smaller infarcts, for every patient without infarction who suffered a hemorrhagic stroke. Conclusions: There is a need for wide debate as to what constitutes an acceptable benefit-risk ratio for thrombolytic therapy; the magnitude of the estimated benefit-risk ratios is such that the advantages of thrombolytic therapy might be made more widely available.