Early effects of tissue-type plasminogen activator added to conventional therapy on the culprit coronary lesion in patients presenting with ischemic cardiac pain at rest. Results of the Thrombolysis in Myocardial Ischemia (TIMI IIIA) Trial.

BACKGROUND: The early effects of tissue-type plasminogen activator (t-PA) on the "culprit" coronary lesion in patients presenting with unstable angina or non-Q wave myocardial infarction were determined by quantitative arteriography. METHODS AND RESULTS: Of 391 such patients, 306 satisfied clinical and arteriographic requirements for eligibility and received a 90-minute front-loaded infusion of t-PA (0.8 mg/kg i.v.; maximum, 80 mg) or placebo plus conventional antianginal therapy. All patients received full heparinization and a follow-up arteriogram 18-48 hours after treatment. A non-Q wave myocardial infarction (MI) was diagnosed in 97 patients (32%) after entry. In the entire patient population, among t-PA- and placebo-treated patients, respectively, 25% versus 19% (p = 0.25) of all culprit lesions achieved the primary study end point, measurable improvement (by > or = 10% reduction of stenosis or two Thrombolysis in Myocardial Infarction [TIMI] flow grades) at follow-up. Substantial improvement (by > or = 20% reduction of stenosis or two TIMI grades) was seen with t-PA in 15% of all culprit lesions versus 5% with placebo (p < 0.003). Arteriographically apparent thrombus was present at baseline in the culprit lesion of 107 patients (35%). Substantial improvement was more frequent with t-PA among lesions containing apparent thrombus (in 36% with t-PA versus 15% with placebo; p < 0.01), as it was among patients evolving a non-Q wave MI (33% versus 8%; p < 0.005). By multivariate analysis, the significant, independent predictors of substantial improvement include apparent thrombus (p = 0.0001), non-Q wave MI (p = 0.003), and t-PA use (p = 0.01). Both non-Q wave MI status and thrombus had been specified a priori as important variables. CONCLUSIONS: Arteriographically apparent intraluminal thrombus and improvement of the culprit lesion with either of these regimens were only moderately frequent in patients with unstable angina or non-Q wave MI. Substantial improvement of culprit lesions was more frequent with t-PA than with placebo overall and in two prospectively defined subgroups. The clinical relevance of these observations is being tested in the larger, ongoing clinical TIMI IIIB study.