Diagnosing acute cardiac ischemia in the emergency department: a systematic review of the accuracy and clinical effect of current technologies.

STUDY OBJECTIVE: Acute cardiac ischemia (ACI) encompasses the diagnoses of unstable angina pectoris and acute myocardial infarction (AMI). Accurate diagnosis and triage of patients with ACI in the emergency department should increase survival for these patients and reduce unnecessary hospital admissions. METHODS: We conducted a systematic review of the English-language literature published between 1966 and December 1998 on the accuracy and clinical effect of diagnostic technologies for ACI. We evaluated prospective and retrospective studies of adult patients who presented to the ED with symptoms suggesting ACI. Outcomes were diagnostic performance (test sensitivity and specificity) and measures of clinical effect. Meta-analyses were performed when appropriate. A decision and cost-effectiveness analysis was conducted that investigated various diagnostic strategies used in the diagnosis of ACI in the ED. RESULTS: We screened 6,667 abstracts, reviewed 407 full articles, and included 106 articles articles in the main analysis. Single measurements of biomarkers at presentation to the ED have low sensitivity for AMI, although they have high specificity. Serial measurements greatly increase the sensitivity for AMI while maintaining their excellent specificity. Diagnostic technologies to evaluate ACI in selected populations, such as electrocardiography, sestamibi perfusion imaging, and stress ECG, may have very good to excellent sensitivity; however, they have not been sufficiently studied. The Goldman Chest Pain Protocol has good sensitivity (about 90%) for AMI but has not been shown to result in any differences in hospitalization rate, length of stay, or estimated costs in the single clinical effect study performed. Its applicability to patients with unstable angina pectoris has not been evaluated. The use of an Acute Cardiac Ischemia-Time-Insensitive Predictive Instrument led to the appropriate triage of 97% of patients with ACI presenting to the ED and reduced unnecessary hospitalizations. CONCLUSION: Many of the current technologies remain underevaluated, especially regarding their clinical effect. The extent to which combinations of tests may provide better accuracy than any single test needs further study.

Accuracy and clinical effect of out-of-hospital electrocardiography in the diagnosis of acute cardiac ischemia: a meta-analysis.

STUDY OBJECTIVE: We sought to evaluate quantitatively the evidence on the diagnostic performance of out-of-hospital ECG for the diagnosis of acute cardiac ischemia (ACI) and acute myocardial infarction (AMI) and the clinical effect of out-of-hospital thrombolysis. METHODS: We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998 on the diagnostic accuracy of out-of-hospital ECG and the clinical effect of out-of-hospital thrombolysis. Both prospective and retrospective studies qualified for the assessment of diagnostic performance. For clinical effect, data from prospective nonrandomized studies were synthesized separately from data from randomized trials. Diagnostic performance was assessed by using estimates of test sensitivity, specificity, and diagnostic odds ratios and was summarized by using summary receiver-operating characteristic curves. Measures of clinical effect included time savings, early ventricular function, early mortality, and long-term survival. RESULTS: Diagnostic accuracy was evaluated in 11 studies with a total of 7,508 patients. Data were available for ACI in 5 studies and for AMI in 8 studies. For ACI, the random-effects pooled sensitivity was 76% (95% CI, 54% to 89%), the specificity was 88% (95% CI, 67% to 96%), and the diagnostic odds ratio was 23 (95% CI, 6.3 to 85). The respective figures for AMI were sensitivity of 68% (95% CI, 59% to 76%), specificity of 97% (95% CI, 89% to 92%), and diagnostic odds ratio of 104 (95% CI, 48 to 224). Both in nonrandomized (n=4, total 1,531 patients) and randomized (n=9, total 6,643 patients) studies, out-of-hospital thrombolysis shortened the time from onset of symptoms to thrombolytic treatment by 40 to 60 minutes. Data on short-term ejection fraction were sparse. Hospital mortality was reduced by 16% (95% CI, 2% to 27%) among randomized trials, and a similar estimate of effect was seen in nonrandomized studies. There was no clear effect on long-term mortality, but data were sparse. CONCLUSION: Out-of-hospital ECG has excellent diagnostic performance for AMI and very good performance for ACI. Out-of-hospital thrombolysis achieves time savings and improves short-term mortality, but the effect on long-term mortality is unknown.

Accuracy of imaging technologies in the diagnosis of acute cardiac ischemia in the emergency department: a meta-analysis.

STUDY OBJECTIVE: We sought to quantitatively evaluate the evidence on the diagnostic performance of imaging technologies (including rest and stress echocardiography and technetium-99m sestamibi scanning) for the diagnosis of acute cardiac ischemia and acute myocardial infarction in the emergency department. METHODS: We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. Both prospective and retrospective studies qualified for the assessment of diagnostic performance. Diagnostic performance was assessed by means of random-effect estimates of test sensitivity, specificity, and the diagnostic odds ratio and was summarized by using summary receiver-operating characteristic curves. RESULTS: Diagnostic accuracy was evaluated in 10 studies of rest echocardiography, 2 studies of dobutamine stress echocardiography, and 6 studies of technetium-99m sestamibi scanning. However, only 3 rest echocardiography and 5 technetium-99m sestamibi studies evaluated patients strictly in the ED setting. Patient populations were often highly selected to represent low- or moderate-risk groups. When limited to ED studies, rest echocardiography showed excellent sensitivity of 93% (95% CI, 81% to 97%) and good specificity of 66% (95% CI, 43% to 83%). The results were similar when all studies were considered, including data from reports of admitted patients and patients sent to the cardiac care unit. There was insufficient literature on stress echocardiography in the ED to properly assess the technology. Technetium-99m sestamibi scanning also showed excellent sensitivity (range, 91.5% to 100%) and good specificity (range, 49.3% to 84.4%) for acute myocardial infarction; for acute cardiac ischemia, the random-effects pooled sensitivity was 89% (95% CI, 73% to 96%), and the pooled specificity was 77% (95% CI, 63% to 87%). CONCLUSION: For selected low- and moderate-risk patient groups, echocardiography and technetium-99m sestamibi imaging appear to have very good diagnostic performance with a similar sensitivity and specificity profile. More evidence should be accumulated on their performance specifically in the ED setting.

Accuracy of biomarkers to diagnose acute cardiac ischemia in the emergency department: a meta-analysis.

STUDY OBJECTIVE: We sought to evaluate quantitatively the evidence on the diagnostic performance of presentation and serial biochemical markers for emergency department diagnosis of acute cardiac ischemia (ACI), including acute myocardial infarction (AMI) and unstable angina. METHODS: We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. We examined the diagnostic performance of creatine kinase, creatine kinase-MB, myoglobin, and troponin I and T testing. Diagnostic performance was assessed by using estimates of test sensitivity and specificity and was summarized by summary receiver-operating characteristic curves. RESULTS: Only 4 studies were found that evaluated all patients with ACI; 73 were found that focused only on a diagnosis of AMI. To diagnose ACI, presentation biomarker tests had sensitivities of 16% to 19% and specificities of 96% to 100%; serial biomarker tests had sensitivities of 31% to 45% and specificities of 95% to 98%. Considering only the diagnosis of AMI, presentation biomarker tests had summary sensitivities of 37% to 49% and summary specificities of 87% to 97%; serial biomarker tests had summary sensitivities of 79% to 93% and summary specificities of 85% to 96%. Variation of test sensitivity was best explained by test timing. Longer symptom duration or time between serial tests yielded higher sensitivity. CONCLUSION: The limited evidence available to evaluate the diagnostic accuracy of biomarkers for ACI suggests that biomarkers have very low sensitivity to diagnose ACI. Thus, biomarkers alone will greatly underdiagnose ACI and will be inadequate to make triage decisions. For AMI diagnosis alone, multiple testing of individual biomarkers over time substantially improves sensitivity, while retaining high specificity, at the expense of additional time. Further high-quality studies are needed on the clinical effect of using biomarkers for patients with ACI in the ED and on optimal timing of serial testing and in combination with other tests.