ST SEGMENT TRACKING FOR RAPID-DETERMINATION OF PATENCY OF THE INFARCT-RELATED ARTERY IN ACUTE MYOCARDIAL-INFARCTION

Objectives. This study was designed to test the hypothesis that monito ring the ST segment on a single electrocardiographic (ECG) lead reflec ting activity in the infarct zone provides sensitive and specific reco gnition of reperfusion within 60 min of initiation of therapy in acute myocardial infarction. Background. Infarct-related arteries that fail to recanalize early may benefit from immediate rescue angioplasty, He nce, detection of reperfusion has important practical clinical implica tions. Methods. Of 41 patients with acute myocardial infarction who ha d ambulatory ECG (Holter) monitors placed, 38 had adequate ST segment monitoring for 3 h; 35 of the 38 were treated with thrombolytic agents and 3 with primary angioplasty, All patients underwent early coronary angiography and were classified into two groups: Group P (22 patients ) had angiographic patency (Thrombolysis in Myocardial Infarction [TIM I] grade 2 or 3 flow), and Group 0 (16 patients) had persistent occlus ion TIMI grade 0 or 1 flow) of the infarct related vessel at 60 min fr om initiation of therapy. The initial ST segment level was defined as the first ST segment level recorded; the peak ST segment level was def ined as the highest ST segment level measured during the 1st 60 min. T o assess the optimal ST segment recovery criteria for reperfusion, the presence or absence of a greater than or equal to 75%, greater than o r equal to 50% and greater than or equal to 25% decrement from initial and peak ST segment levels, sampled and analyzed at 2.5-, 5-, 10, 15- and 20-min intervals, was correlated,vith patency of the infarct-rela ted artery at 60 min. Results. ST segment recovery of greater than or equal to 50% reduction from peak ST segment levels with sampling rates at less than or equal to 10-min intervals provided the optimal criter ion for recognizing coronary artery patency at 60 min (sensitivity 96% , 95% confidence interval [CI] 77% to 99%; specificity 94%, 95% CI 69% to 99%, p < 0.00001). The subgroup of 13 patients in Group P with TIM I grade 3 reperfusion flow all met this criterion (sensitivity 100%, 9 5% CI 75% to 100%). The use of the initial ST segment level as the bas eline for determining the presence of a greater than or equal to 50% r eduction in ST segment levels within 60 min was less sensitive. Predic tion of coronary reperfusion within 60 min of therapy on the basis of a greater than or equal to 75% decrement from peak ST segment levels w as less sensitive, and the use of a greater than or equal to 25% decre ment was less specific. Conclusions. ST segment monitoring of a single lead reflecting the infarct zone provides a reliable method for asses sing reperfusion within 60 min of acute myocardial infarction. Optimal criteria for ECG reperfusion include a greater than or equal to 50% d ecrease from peak ST segment levels, with ST segment measurements reco rded continuously or at least every 10 min.