Combined historical and electrocardiographic timing of acute anterior and inferior myocardial infarcts for prediction of reperfusion achievable size limitation

The historical time of acute symptom onset is not always an accurate indica tion of the timing of onset of an acute myocardial infarction (AMI). Consid eration of electrocardiographic (ECG) timing parameters could supplement hi storical timing alone as a clinical guide for decisions regarding the use o f reperfusion therapy. Three hundred ninety-five patients from 4 trials of thrombolytic therapy conducted in the northwestern United States and wester n Canada are included in the present study. A total of 316 patients receive d either streptokinase or tissue plasminogen activator, and 79 received no reperfusion therapy. Historical time of symptom onset was acquired by emerg ency or cardiology department personnel and recorded on patient report form s. An ECG method for estimating the timing of the AMI, the Anderson-Wilkins (AW) acuteness score, was calculated from the initial standard 12-lead rec ording by investigators blinded to the knowledge of symptom duration or any other study variables. Tomographic thallium-201 imaging 7 weeks after hosp ital admission was used to measure final AMI size. The ECG timing method ac hieved a relation with final AMI size similar tot that previously reported for historical timing. The AW acuteness score proved most useful for anteri or AMI location when there was a greater than or equal to 2 hour delay foll owing symptom onset, but was most useful far the inferior AMI location when there was a <2 hour delay. Despite a longer delay, patients with high AW a cuteness scores had 50% lower final anterior AMI size than those with low s cores; and despite a shorter delay, those with tow ECG acuteness scores had 50% greater final inferior AMI size than those with high scores. The AW ac uteness score combined with the historical estimation of symptom duration s hould provide a more accurate basis for predicting the potential for limita tion of final AMI size than either method alone, These results could potent ially provide the basis for developing a new method far noninvasive guidanc e of clinical decisions regarding administration of reperfusion therapy in the initial evaluation of patients with AMI. (C) 1999 by Excerpta Medica, I nc.