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.