Early versus late opening of coronary arteries: the effect of timing.

Intuitively, one would assume that the benefit from the use of thrombolytic therapy in reducing mortality in acute myocardial infarction (AMI) is directly related to early recanalization of the thrombosed infarct-related artery. However, a meta-analysis of early clinical trials and the ISIS-II trial results suggests that thrombolysis initiated between 6 and 24 h after the onset of infarction still reduces mortality. Verification of this observation is currently being sought in three ongoing trials of late reperfusion. These are the EMERA trial in South America, using streptokinase; the LATE study involving several European countries, the United States, Canada, and Australia, using tissue plasminogen activator (tPA); and the TAMI-6 trial, in which either tPA or placebo is given 6 to 24 h postinfarction, and patients with closed infarct-related arteries are randomized further to either angioplasty or no angioplasty. There are theoretical reasons that late reperfusion may be beneficial. These reasons include the prevention of infarct expansion and ventricular remodeling leading to ventricular dilatation, the provision of electrophysiologic stability lessening the likelihood of malignant ventricular arrhythmias, and the ability of collaterals emanating from the recanalized artery to perfuse ischemic but still viable myocardium. There are also reasons that late reperfusion might be harmful, including myocardial stunning, microvascular damage, and intramyocardial hemorrhage leading to an increased likelihood of myocardial rupture. It does appear, however, that once recanalization occurs, maintenance of patency improves late outcome, as shown in the Western Washington Intracoronary Streptokinase Trial, the TAMI trial, the TIMI trial, and the Duke study.(ABSTRACT TRUNCATED AT 250 WORDS)