In patients treated with primary coronary angioplasty, the use of abciximab improves microvascular perfusion and enhances the recovery of contractile function. This study compared the effects of the new dose regimen of tirofiban (25-microg/kg bolus followed by an 18-hour infusion at 0.15 microg/kg/min) on left ventricular function with those of abciximab in patients who underwent direct angioplasty. One hundred patients who underwent primary coronary angioplasty were randomized to receive a standard dose of abciximab or a large-dose bolus of tirofiban. The primary end point of the study was change in the infarct-zone wall motion score index between the initial and 30-day follow-up echocardiographic studies. The secondary end points were procedural evaluations before and after Thrombolysis In Myocardial Infarction (TIMI) grade flow, TIMI grade myocardial perfusion, and corrected TIMI frame count. Baseline global and regional ventricular functions were similar in the 2 treatment groups. After the procedure, a TIMI grade 3 flow was obtained in 86% of patients treated with abciximab and 88% of those receiving tirofiban (p = 1.0), whereas TIMI grade 3 myocardial perfusion was present in 70% and 76%, respectively (p = 0.65); corrected TIMI frame count was 22.5 +/- 1.9 and 22.1 +/- 2.5 (p = 0.37). After 30 days, we obtained 87 paired echocardiographic studies. The infarct-zone wall motion score index decreased from 2.20 +/- 0.3 to 1.99 +/- 0.2 in the abciximab group and from 2.18 +/- 0.3 to 1.95 +/- 0.3 in the tirofiban group (p = 0.67). Thus, in patients who had primary coronary angioplasty, abciximab, and the large-dose bolus of tirofiban showed similar effects on the initial angiographic results and 30-day recovery of left ventricular function.