Electrocardiographic Markers of Reperfusion in ST-elevation Myocardial Infarction

At present, bedside recognition of reperfusion in patients presenting with acute STEMI can be accomplished best by assessment of several objective and subjective signs of termination of ischemia (ie, resolution of chest pain or rapid STR). A study by Oude Ophuis and colleagues [69] of 230 patients who had STEMI suggested that the combination of ECG and clinical markers may better predict the patency of the IRA and the status of myocardial reperfusion. They found that a sudden decrease in chest pain was the most common sign of reperfusion (36%), followed by STR of 50% or more (30%), and the development of a terminal negative T wave (20%) in the lead with the highest ST elevation. STR of 50% or more and the appearance of AIVR had the highest positive predictive value for reperfusion. For TIMI grade 3 flow, the positive predictive value of STR was 66% and for AIVR it was 59%. The presence of three or more noninvasive markers of reperfusion predicted TIMI grade 3 flow accurately in 80% of cases. Because ST segments may fluctuate dramatically before and during thrombolytic therapy, an accurate determination of progressive decrease (by ≥ 50%) relative to the highest ST elevation requires frequent (every 5-15 minutes) or continuous monitoring of ST (in either a selected lead or all 12 leads). Although other bedside signs such as AIVR and Bezold-Jarisch reflex also indicate reperfusion, their limited sensitivity restricts their usefulness. Biochemical markers related to accelerated washout associated with reperfusion, although promising, are still limited in their usefulness because the results are difficult to obtain in a timely fashion. Acute coronary angiography, although useful, is not practical, and it may turn out not to be the reference standard for reperfusion. Because the goal of reperfusion is to achieve termination of ongoing ischemia, noninvasive markers of ischemia termination may be a better standard than the anatomic evidence obtained by coronary angiography. The favorable prognostic impact of early STR in reperfusion trials supports the clinical relevance and importance of signs of ischemia termination. It is necessary, however, to improve the understanding of the pathophysiologic mechanisms leading to the ECG changes during reperfusion, namely the significance of STR, T-wave configuration, and early and terminal QRS complex changes. Better understanding of the pathophysiology may help in the design of studies to examine specific interventions (ie, intravenous glycoprotein IIb/IIIa inhibitors, clopidogrel, nitrates, adenosine, and other drugs) that may be beneficial in patients who have not reached complete ECG signs of reperfusion (STR with complete T-wave inversion).