The Dynamic Nature of ST-Segment and T-Wave Changes During Acute MI

Abstract

Obtaining aprehospital 12-lead electrocardiogram (ECG) diagnostic of acute myocardial injury has been demonstrated to hasten the administration of thrombolytic agents in the emergency department. This case demonstrates that aprehospital electrocardiogram diagnostic of acute anterior wall infarction can become non-diagnostic following routine administration of oxygen, nitroglycerin, and morphine by paramedics. Although this phenomenon has been observed in the in-hospital setting, it has not been reported in patients with a prehospital ECG.

Information on Myocardial Ischemia and Arrhythmias Added by Prehospital Electrocardiograms

“…21 The resolution of ST-segment elevation and depression observed in our study may be related to prehospital therapies, including oxygen and nitroglycerin. 27,28 Complete, reliable data on prehospital medications are not available for our study patients. However, a majority are expected to have received nitroglycerin, aspirin, and oxygen, unless con-traindicated, since the EMS protocols for these prehospital medications and for ECG acquisition were very similar for patients with a suspected acute ischemic event in our region.…”

Potential diversion rates associated with prehospital acute myocardial infarction triage strategies

“…On the one hand, the use of clinical data obtained later in the course of the patient's care may reveal additional diagnostic information that was not seen in the prehospital phase of care (e.g., EKG changes that appear with progression of the AMI). On the other hand, the administration of oxygen, nitroglycerin, and morphine to symptomatic patients with ACS by paramedics tends to result in the resolution of symptoms and EKG changes suggestive of cardiac ischemia, so ischemic symptoms and electrocardiographic evidence of AMI that could be seen in the prehospital setting may, in some cases, resolve before ED arrival (51).…”