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Pre-hospital ECG May Reduce Reperfusion Times
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Diercks D, et al. Utilization and impact of pre-hospital electrocardiograms for patients with acute ST-segment elevation myocardial infarction: Data from the NCDR (National Cardiovascular Data Registry) ACTION (Acute Coronary Treatment and Intervention Outcomes Network) registry. J Am Coll Cardiol. 2009;53:161-166.
The goal of treatment during ST elevation myocardial infarction (STEMI) is early reperfusion of the occluded coronary artery, as this has been shown to reduce mortality and morbidity. Accordingly, national guidelines emphasize rapid treatment times (door-to-needle time < 30 minutes for fibrinolysis and door-to-balloon time < 90 minutes for primary percutaneous coronary intervention [PCI]). Recent interest has focused on developing regional protocols for pre-hospital, 12-lead electrocardiograms (ECGs) by emergency medical staff (EMS) in the ambulance prior to hospital arrival, in order to mobilize in-hospital systems in advance to improve these treatment times. Using data from the National Cardiovascular Data Registry (NCDR) Acute Coronary Treatment and Intervention Outcomes Network (ACTION) registry, Diercks et al analyzed the effect of EMS 12-lead ECG on door-to-balloon and door-to-needle times.
From 271 participating hospitals, data were reported on 19,481 patients presenting with STEMI. For their analysis, Diercks et al included 12,097 patients with complete data. Of these, 58.7% (7,098) were transported to the ACTION-participating hospital by EMS. Patients transported by EMS tended to be sicker than those who arrived by other means. They were older; were less commonly male; more commonly had prior myocardial infarction (MI), prior congestive heart failure (CHF), and signs of CHF on presentation; and shorter times from symptom onset to hospital presentation compared with patients who were self-transported to the ACTION-participating hospital. Of the EMS-transported patients, 24.7% (1,941) received a pre-hospital ECG. Patients with a pre-hospital ECG were more commonly male and less commonly had diabetes and left bundle branch block or signs of CHF on presentation compared with patients with an in-hospital ECG. The time from symptom onset to hospital presentation was similar between these groups.
Patients who received a pre-hospital ECG were more likely to undergo primary PCI and were less likely to have reperfusion therapy withheld. Patients receiving pre-hospital ECG had shorter door-to-balloon times (61 mins. vs 75 mins.; p < 0.0001) and shorter door-to-needle times (19 mins. vs 29 mins.; p = 0.003), and this difference persisted when stratified by presentation during working hours or after hours. In addition, they were more likely to receive aspirin, clopidogrel, and glycoprotein IIb/IIIa inhibitors within the first 24 hours. There was a non-significant trend toward reduction in in-hospital mortality, heart failure, and shock in patients receiving a pre-hospital ECG. Among patients who received any reperfusion therapy, the use of pre-hospital ECG did not alter risk-adjusted mortality. Diercks et al concluded that the use of pre-hospital ECG was associated with a greater use of reperfusion therapy, faster reperfusion times, and a trend for lower risk-adjusted, in-hospital mortality.
Rapid reperfusion of an occluded infarct artery remains the most powerful weapon against early death and heart failure during ST elevation MI. Recently, there has been a nationwide move toward systems that will improve the time-to-reperfusion and improve adherence to guidelines for reperfusion times. The institution of pre-hospital ECGs has been shown to reduce reperfusion times in regional studies yet, interestingly, only 20% of patients transported by EMS have a pre-hospital ECG performed. It is important to note that regions throughout the country differ on how easily and successfully this could be instituted for numerous social, financial, geographical, and political reasons. The present study by Diercks et al presents amalgamated data from around the country through the ACTION NCDR registry and, thus, shows this is possible on a wider scale.
This study is a registry report, not a prospective, randomized trial and, therefore, can only be as accurate as the data that is input from each site. There may be unmeasured confounders between those patients receiving and those not receiving pre-hospital ECGs. Also, it is not clear whether the ECGs were read by the EMS providers, automated readouts, or by transmission to physicians. In addition, around one-third of patients were excluded from the analysis, limiting the generalizability of the results. However, despite these limitations, the results are exciting, and should be taken into account by any region considering a pre-hospital ECG program.