 There is now unequivocal evidence that early coronary reperfusion using either thrombolytics or primary angioplasty results in a long-term mortality reduction among individuals who have had a heart attack. The benefit of early reperfusion less than 6 hours after the heart attack was initially attributed to myocardial salvage and the resultant preservation of left ventricular function. However, it is now known that the survival benefit associated with thrombolytic therapy is not consistently associated with a major improvement in left ventricular ejection fraction LVEF. These observations led to the formulation of the late open artery hypothesis, which suggests that clinical outcomes can potentially be improved by late reperfusion after a heart attack. Observational clinical studies have suggested that late patency of the infarct-related artery IRA after thrombolysis is associated with a survival benefit that is independent of LVEF and therefore cannot be solely explained by salvage of myocardium. Definitive proof of the late open artery hypothesis is currently lacking, however, because previous studies that have evaluated late percutaneous transluminal coronary angioplasty PTCA of occluded IRAs after a heart attack have produced conflicting results. 