The STEMI versus non-STEMI distinction is unreliable in emergency decision making in patients with ACS for several reasons I have posted before. This study illustrates yet another reason:
Objective. To determine the prevalence and significance of ST-segment elevation resolution between prehospital and first hospital ECG...Results. We reviewed 24,197 prehospital ECGs and identified 293 cases of prehospital STEMI. Complete hospital and prehospital records were available for 83 cases (28%)...STR occurred in 18 cases (22%, CI 14–32%). There were no differences between STR and non-STR cases in prehospital vital signs or treatments. 95% of patients underwent cardiac catheterization with a mean door-to-needle time of 57 minutes (interquartile range 43–71). Comparing STR and non-STR cases, significant lesions (greater than or equal to 50%) were found in 94 and 97% of patients (p = 0.6), and subtotal or total lesions (greater than or equal to 95%) were found in 63 and 85% (p = 0.1), respectively. Conclusions. We found that ST-segment resolution occurred prior to catheterization in 1 of 5 patients with prehospital STEMI, emphasizing the necessity of prehospital ECG in risk stratification of patients with suspected coronary disease. Coronary lesions and intervention rates did not differ between STR and non-STR, suggesting that catheterization is warranted even when STEMI criteria are no longer met in-hospital.
Acute coronary syndromes, as we've known ever since studies involving coronary angioscopy in the 1980s, are dynamic states of thrombus, lysis and reformation. What presents as NSTEMI to the ER may have been a STEMI only moments prior.