One-year results of the Thrombolysis in Myocardial Infarction (TIMI) IIIB clinical trial. A randomized comparison of tissue-type plasminogen activator versus placebo and early invasive versus early conservative strategies in unstable angina and non-Q wave myocardial infarction.

OBJECTIVES

We report mortality, infarction, revascularization and repeat hospital admission events for 1 year after enrollment and randomization in the Thrombolysis in Myocardial Ischemia (TIMI) IIIB clinical trial.

BACKGROUND

The purpose of this trial was to investigate the role of a thrombolytic agent added to conventional medical therapies and to compare an early invasive management strategy to a more conservative early strategy in patients with unstable angina and non-Q wave myocardial infarction.

METHODS

There were 1,473 patients enrolled, and they received conventional anti-ischemic medical therapies. They were randomized to therapy with either tissue-type plasminogen activator (t-PA) or placebo and also to an early invasive management strategy with coronary arteriography at 18 to 48 h, followed by revascularization as soon as possible if appropriate, or, alternatively, to an early conservative strategy with arteriography and revascularization reserved for failure of initial therapy to prevent recurrent ischemia. The primary end point was a composite outcome variable and was assessed at 42 days. Patients were then managed entirely at the discretion of their treating physician. Follow-up contacts were made at 1 year.

RESULTS

The incidence of death or nonfatal infarction for the t-PA- and placebo-treated groups was similar after 1 year (12.4% vs. 10.6%, p = 0.24). The incidence of death or nonfatal infarction was also similar after 1 year for the early invasive and early conservative strategies (10.8% vs. 12.2%, p = 0.42). A trial of this size should be able to detect differences in relative risk for death or infarction > or = 1.81 with a power of 80% at a significance level (alpha) of 0.01. Revascularization by 1 year was common, but was slightly more common with the early invasive than the early conservative strategy (64% vs. 58%, p < 0.001). This result was related entirely to a small difference in angioplasty rates (39% vs. 32%, p < 0.001) inasmuch as rates of bypass grafting by 1 year were equivalent (30% in each group, p = 0.50). The high rate of revascularization in both strategies was accompanied by comparable clinical status at the 1-year follow-up contact.

CONCLUSIONS

In this large study of unstable angina and non-Q wave myocardial infarction, the incidence of death and nonfatal infarction or reinfarction was low but not trivial after 1 year (4.3% mortality, 8.8% nonfatal infarction). An early invasive management strategy was associated with slightly more coronary angioplasty procedures but equivalent numbers of bypass surgery procedures than a more conservative early strategy of catheterization and revascularization only for signs of recurrent ischemia. The incidence of death or nonfatal infarction, or both, did not differ after 1 year by strategy assignment, but fewer patients in the early invasive strategy group underwent later repeat hospital admission (26% vs. 33%, p < 0.001). Either strategy is appropriate for patient management; differences in hospital admissions and revascularization procedures, with their attendant costs, are likely to be minimal.