Information on Myocardial Ischemia and Arrhythmias Added by Prehospital Electrocardiograms

Abstract

Background. The prehospital electrocardiogram (ECG) allows earlier identification of acute ST-segment elevation myocardial infarction (STEMI). Its utility for detection of other acute cardiac events, as well as for transient ST-segment abnormalities no longer present when the first hospital ECG is performed, is not well characterized. Objective. We sought to examine whether the prehospital ECG adds supplemental information to the first ECG obtained in hospital, by comparing data on possible cardiac ischemia and arrhythmias provided by the two ECGs, in ambulance patients later diagnosed as having cardiac disorders, including STEMI. Methods. Ambulance personnel acquired 12-lead ECGs for patients suspected of having an acute ischemic event, prior to transport to hospital. The first emergency department 12-lead ECG was provided by medical records at the receiving hospital, and the principal hospital diagnosis for the event was extracted from chart data. Two cardiologists, blinded to the hospital diagnosis, provided their consensus interpretation of 1,209 pairs of ECGs, noting the presence or absence of specific abnormalities on each tracing. Results. Among the 82 patients who had an eventual hospital diagnosis of STEMI, the study cardiologists identified 71 with ST-segment elevations on the ECGs they examined. The vast majority of these (97%) were observed on both ECGs, but the prehospital ECG showed ST-segment elevation for two additional patients (3%). No additional instances were seen only on the hospital ECG. Among the 116 patients with a hospital diagnosis of non–ST-segment elevation myocardial infarction (NSTEMI), the cardiologists identified 36 with ST-segment depressions: 28 (78%) of these were present on both ECGs, seven (19%) only on the prehospital ECG, and one (3%) only on the hospital ECG. Among the 567 patients with any cardiac hospital diagnosis, the cardiologists identified 87 with arrhythmias: 73 (84%) on both ECGs, 12 (14%) only on the prehospital ECG, and two (2%) only on the hospital ECG. Conclusions. Beyond identifying ST-segment elevation earlier, prehospital ECGs detect important transient abnormalities, information not otherwise available from the first emergency department ECG. These data can expedite diagnosis and clinical management decisions among patients suspected of having an acute cardiac event. The prehospital ECG should be fully integrated into emergency medicine practice.

Key words: :

• electrocardiography
• emergency medicine
• acute myocardial infarction
• ischemia
• arrhythmias
• patient care management