The purpose of this medical research study is to determine whether abciximab given in combination with reteplase, before patients have a coronary intervention (a standard treatment where a catheter is inserted into the heart artery to get blood flowing past the clot), is safe and effective in the treatment of heart attacks compared to only abciximab given during coronary intervention. This medical research study will also help determine if the combination of abciximab and reduced dose reteplase will decrease the risk of death, and reduce complications of a heart attack at 90 days compared to abciximab alone which is a standard treatment.