In this multicenter prospective trial, we studied posterior (V₇ to V₉) and right ventricular (V₄R to V₆R) leads to assess their accuracy compared with standard 12-lead electrocardiograms (ECGs) for the diagnosis of acute myocardial infarction (AMI). Patients aged >34 years with suspected AMI received posterior and right ventricular leads immediately after the initial 12-lead ECG. ST elevation of 0.1 mV in 2 leads was blindly determined and inter-rater reliability estimated. AMI was diagnosed by World Health Organization criteria. The diagnostic value of nonstandard leads was determined when 12-lead ST elevation was absent and present and multivariate stepwise regression analysis was also performed. Of 533 study patients, 64.7% (345 of 533) had AMI and 24.8% received thrombolytic therapy. Posterior and right ventricular leads increased sensitivity for AMI by 8.4% (p = 0.03) but decreased specificity by 7.0% (p = 0.06). The likelihood ratios of a positive test for 12, 12 + posterior, and 12 + right ventricular ECGs were 6.4, 5.6, and 4.5, respectively. Increased AMI rates (positive predictive values) were found when ST elevation was present on 6 nonstandard leads (69.1%), on 12 leads only (88.4%), and on both 6 and 12 leads (96.8%; p <0.001). Treatment rates with thrombolytic therapy increased in parallel with this electrocardiographic gradient. Logistic regression analysis showed that 4 leads were independently predictive of AMI (p <0.001): leads I, II, V₃, V₅R; V₉ approached statistical significance (p = 0.055). The standard ECG is not optimal for detecting ST-segment elevation in AMI, but its accuracy is only modestly improved by the addition of posterior and right ventricular leads.

In this multicenter prospective trial, 0.1 mV of ST-segment elevation in posterior (V₇ to V₉) and right ventricular (V₄R to V₆R) leads was found to increase the sensitivity of the electrocardiogram for acute myocardial infarction by 8.4% (p = 0.03), but decrease specificity by 7.0% (p = 0.06); logistic regression analysis showed that 4 leads were predictive of AMI at p <0.001: I, II, V₃, V₅; V₉ approached statistical significance (p = 0.055). The standard electrocardiogram is not optimal for detecting ST elevation in acute myocardial infarction, but its accuracy is only modestly improved by the addition of posterior and right ventricular leads.