Abstract 17595: The Value of Continuous ST-Segment Monitoring in the Emergency Department: a Quasi-Experimental Pre-Post Study

Abstract

Purpose: The AHA Practice Standards for ECG Monitoring recommend continuous ST-segment monitoring (C-STM) in patients presenting to the emergency department (ED) with signs and/or symptoms suggestive of acute coronary syndrome (ACS), but few studies have evaluated its use in the ED. Our aims were to compare the time to diagnosis and 30-day adverse events (return to the ED with signs and/or symptoms of ACS, hospital admission, acute myocardial infarction, use of reperfusion therapy, or mortality) before and after implementation of C-STM. We also evaluated the diagnostic accuracy of C-STM in detecting ischemia or infarction, using stress test and troponin I results as reference standards. Methods: We prospectively studied 163 adults (pre-intervention phase: n=78; intervention phase: n=85) in the ED at a single hospital. We stratified patients into low (n=51), intermediate (n=100), or high (n=12) risk using HEART scores. The principal investigator monitored participants, activating C-STM on bedside monitors in the intervention phase. We used likelihood ratios (LRs) as the measure of diagnostic accuracy. By convention, a positive (+) LR is diagnostic at >10 and a negative (-) LR at <0.1. Results: Overall, 9% of patients were diagnosed with ACS. There was no significant difference in median time to ACS diagnosis before and after implementation of C-STM (5.55 vs. 5.98 hours; p=0.43 for Mann-Whitney U test). In risk-stratified analyses, no significant pre-post difference in time to ACS diagnosis was found in low-, intermediate-, or high-risk patients. There was no difference in the rate of any 30-day adverse event before vs. after C-STM implementation (11.5% vs. 10.6%; p=0.85 Chi-squared test). None of 3 episodes of ST-segment changes on C-STM represented ACS. The +LR and -LR of C-STM for ischemia were 24.0 (95% CI 1.4 - 412.0) and 0.3 (95% CI 0.02 - 2.9), respectively; and for infarction were 13.7 (95% CI 1.7 - 112.3) and 0.7 (95% CI 0.3 - 1.5), respectively. Conclusion: In this sample of mainly low- to intermediate-risk patients, use of C-STM did not improve time to diagnosis or 30-day adverse outcomes, nor provide much benefit in detecting myocardial ischemia or infarction. Use of C-STM may need to be re-evaluated for patients with low to intermediate risk for ACS in the ED.