Is it possible to exclude a diagnosis of myocardial damage within six hours of admission to an emergency department? Diagnostic cohort

Abstract

Objective To assess the clinical efficacy and accuracy of an emergency department based six hour rule-out protocol for myocardial damage. Design Diagnostic cohort study. Setting Emergency department of an inner city university hospital. Participants 383 consecutive patients aged over 25 years with chest pain of less than 12 hours' duration who were at low to moderate risk of acute myocardial infarction. Intervention Serial measurements of creatine kinase MB mass and continuous ST segment monitoring for six hours with 12 leads. Main outcome measure Performance of the diagnostic test against a gold standard consisting of either a 48 hour measurement of troponin T concentration or screening for myocardial infarction according to the World Health Organization's criteria. Results Outcome of the gold standard test was available for 292 patients. On the diagnostic test for the protocol, 53 patients had positive results and 239 patients had negative results. There were 18 false positive results and one false negative result. Sensitivity was 97.2% (95% confidence interval 95.0% to 99.0%), specificity 93.0% (90.0% to 96.0%), the negative predictive value 99.6%, and the positive predictive value 66.0%. The positive likelihood ratio was 13.9 and the negative likelihood ratio 0.03. Conclusions The six hour rule-out protocol for myocardial infarction is accurate and efficacious. It can be used in patients presenting to emergency departments with chest pain indicating a low to moderate risk of myocardial infarction.

Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings: A Scientific Statement From the American Heart Association

“…Among 383 consecutive patients with chest pain, 6 demonstrated STsegment changes on contin uous monitoring, leading to early identification of an evolving MI for 2 of these who subsequently received thrombolytics. 29 Among 968 patients with ACS (the majority of whom had NSTEMI or unstable angina), the conventional 12 lead ECG lacked sensitivity, failing to detect Twave or STsegment changes in 80% of these patients. 140 By im plementation of a 12lead ECG from 5 electrodes and continuous STsegment monitoring transmitted via tele phone to the local EDs in northern California, patients (n=4219) with symptoms of ACS had a faster time to first intravenous drug; among patients with STEMI, there was a trend toward faster doortoballoon time and lower mortality risk.…”

“…A 6h ruleout protocol using cardiac markers and continuous ST segment monitoring for MI among patients in a chest pain unit demonstrated STsegment changes on continuous monitoring for 6 patients, leading to early identification of an evolving MI for 2 of these who subsequently received thrombolytics (Herren et al 29 ).…”

View From the United Kingdom

“…10 Concerns about the safety of exercise testing in the acute setting have largely been answered, 17,18 but other concerns persist. First, awareness of the limited specificity of exercise testing has raised the concern that its use in a low-risk population will generate large number of false positive tests and a consequent rise in referrals for coronary angiography.…”

National Survey of Cardiologists’ Standard of Practice for Continuous ST-Segment Monitoring

“…Chest pain units and investigators who examined methods to rule out myocardial infarction have included continuous or automated monitoring in their protocols. [19][20][21] Along with cardiac serum markers, continuous ST-segment monitoring is an accurate predictor of patients' prognosis. 3,5,8,13,15 Maas et al 13 used a prospective, comparative design to examine age, heart rate, and late ST-segment elevation as independent risk factors for adverse clinical outcomes among 1777 patients.…”