Non-invasive detection of early infarct vessel patency by resolution of ST-segment elevation in patients with thrombolysis for acute myocardial infarction; results of the angiographic substudy of the Hirudin for Improvement of Thrombolysis (HIT)-4 trial.

Aims The purpose of this study was to validate ST segment resolution as a non-invasive marker for patency of the infarct-related artery 90 min after the start of streptokinase therapy in patients with acute myocardial infarction. Methods and Results In the HIT-4 angiographic substudy, 447 patients with acute myocardial infarction </=6 h received 1.5 million IU streptokinase. Angiograms of the infarct vessel were obtained after 90 min and 12-lead ECGs at baseline and after 90 min. The best cut-off points for a correct prediction of 90 min infarct vessel patency (TIMI 2/3 flow) and complete patency (TIMI 3) were 30% ST resolution and 40% ST resolution, respectively (specificity 68% and 69%, sensitivity 76% and 75%). Prediction of infarct vessel patency by ST resolution in steps of 10% displayed a gradual increase in patency rates. Patients with > or =70% ST resolution (n=70) had a 92% probability of TIMI 2/3 flow, while <30% ST resolution (n=172) was associated with the absence of TIMI 3 flow in 84% of patients. Conclusions Despite fairly good sensitivities and specificities the prediction of infarct vessel patency by ST resolution in the individual patient is limited. However, patients with > or =70% ST resolution are likely to have a patent infarct artery and <30% ST resolution predicts epicardial vessel occlusion or, since persistent ST elevation reflects the existing ischaemic myocardial injury, absence of myocardial perfusion.