Diagnostic value of the electrocardiogram in the assessment of prior myocardial infarction

BACKGROUND: The best available imaging technique for the detection of prior myocardial infarction (MI) is cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE). Although the electrocardiogram (ECG) still plays a major role in the diagnosis of prior MI, the diagnostic value of the ECG remains uncertain. This study evaluates the diagnostic value of the ECG in the assessment of prior MI. METHODS: In this retrospective study, data from electronic patient files were collected of 1033 patients who had undergone CMR with LGE between January 2014 and December 2017. After the exclusion of 59 patients, the data of 974 patients were analysed. Twelve-lead ECGs were blinded and evaluated for signs of prior MI by two cardiologists separately. Disagreement in interpretation was resolved by the judgement of a third cardiologist. Outcomes of CMR with LGE were used as the gold standard. RESULTS: The sensitivity of the ECG in the detection of MI was 38.0% with a 95% confidence interval (CI) of 31.6-44.8%. The specificity was 86.9% (95% CI 84.4-89.1%). The positive and negative predictive value were 43.6% (95% CI 36.4-50.9%) and 84.0% (95% CI 81.4-86.5%) respectively. In 170 ECGs (17.5%), the two cardiologists disagreed on the presence or absence of MI. Inter-rater variability was moderate (κ 0.51, 95% CI 0.45-0.58, p < 0.001). CONCLUSION: The ECG has a low diagnostic value in the detection of prior MI. However, if the ECG shows no signs of prior MI, the absence of MI is likely. This study confirms that a history of MI should not be based solely on an ECG.