From STEMI to occlusion MI: paradigm shift and ED quality improvement

A generation ago the ST-elevation myocardial infarction (STEMI) paradigm led to quality improvement (QI) in the emergency department (ED).Now, insights from angiography and advances in electrocardiogram (ECG) interpretation have led to the new paradigm of occlusion myocardial infarction (OMI), creating the possibility of further QI.This article reviews the current STEMI paradigm, the emergence of the OMI paradigm, and the use of QI to continuously improve care for acute myocardial infarction (AMI) patients in the ED. STEMI paradigm and QIThrombolytic therapy in the 1990s led to a paradigm shift in the treatment of AMI through emergent reperfusion.This changed the use of the ECG, from retrospectively classifying AMI into Q-wave/non-Q wave to prospectively identifying those with ST elevation, as a marker of AMIs with persistent occlusion without collateral circulation, which need emergent reperfusion.ED providers responded with QI initiatives to reduce reperfusion delays for AMIs with ST elevation, or STEMI, from emergency nurse-initiated ECG acquisition to emergency physician-initiated cath lab activation.However, from the beginning of the STEMI paradigm there were questions about ECG interpretation at the heart of the diagnostic process.A 1994 report on ED delays published in Annals of Emergency Medicine summarized, "ECG abnormalities may be subtle or open to different interpretation, such as early repolarization or pericarditis.Only borderline or minimal ST-segment elevation may be present, and the emergency physician may be uncertain of its significance.The presence of left bundle branch block or left ventricular hypertrophy may complicate ECG diagnosis.The emergency physician may suspect that the ST elevation is old, but a previous ECG may be unavailable for comparison.The computer interpretation of the ECG on which some physicians rely may be incorrect.The emergency physician may not be sufficiently trained to recognize certain ECG patterns as signs of AMI" [1].At the time little could be done to improve on these quality issues.Those that did not meet STEMI criteria were labeled "non-STEMI" (NSTEMI) and did not receive emergent reperfusion.But in the nearly 30 years since this paradigm emerged, insights from angiography and advances in ECG interpretation have identified the limits of this paradigm and given rise to a new one.