Comparison of STEMI and NSTEMI patients in the emergency department

Abstract

Acute myocardial infarction (MI) significantly contributes to mortality and morbidity in developed and developing countries. ECG can readily diagnose ST-elevation myocardial infarction (STEMI) to allow myocardium-saving interventions; however, ECG is not effective for diagnosing patients with non-ST-elevation myocardial infarction (NSTEMI). We performed this study to compare NSTEMI patients to their STEMI counterparts to find useful clues that may be helpful for early diagnosis of NSTEMI. We reviewed the patients who received percutaneous coronary intervention (PCI) in our hospital from January 1st 2009 to May 31st 2010. Acute MI was diagnosed based on the clinical manifestation, ECG, and a rise in cardiac markers. Acute MI patients were classified as either STEMI or NSTEMI. Their chronographs, coronary risks, co-morbidity, ECG, echocardiogram, angiographic findings, interventions, and short-term outcomes were collected. We used the Student's t -test, a chi-squared test, and the multivariate logistic regression analysis to compare the STEMI and NSTEMI patients; p < 0.05 was defined to be statistically significant. There were 417 patients who received PCI, and 175 (42.0%) of them were diagnosed to have acute MI. There were 168 patients enrolled for analysis: 104 patients (61.9%) had STEMI and 64 (38.1%) had NSTEMI. The male/female ratio was greater in STEMI (4.0 vs 1.9; p = 0.041). A higher percentage of NSTEMI patients had end-stage renal diseases ( p < 0.001), or cerebrovascular diseases ( p = 0.030), and received coronary intervention ( p = 0.015) before the index MI. NSTEMI patients had less wall motion abnormality ( p = 0.0045). The left anterior descending artery was the most common culprit artery; however, the left circumflex artery was involved more commonly in NSTEMI than in STEMI ( p < 0.001). Among NSTEMI patients, 22 (34.4%) had ST depression. Forty-two had other ECG changes: T wave abnormalities (33; 51.6%), poor R-wave progression (4; 6.3%), atrial fibrillation (3; 4.7%), bundle branch block (2; 3.1%), frequent PVCs (1; 1.6%), and asystole (1; 1.6%). One patient displayed no change (1; 1.6%). Early diagnosis is the first step of successful treatment in acute MI. Although new diagnostic methods are continuously developed, the 12-lead body surface ECG remains the single most important initial clinical test for myocardial ischemia and infarction. For potential NSTEMI patients, we should obtain serial ECGs for comparison. Expert consultation, assisted by bedside echocardiography, and laboratory measurement of cardiac markers, should be undertaken without delay once dynamic, though subtle, ECG changes are found.