Prevalence and incidence of Q-wave unrecognized myocardial infarction in general population: Diagnostic value of the electrocardiogram. The REGICOR study.

BACKGROUND: Diagnosis of unrecognized myocardial infarction (UMI) remains an open question in epidemiological and clinical studies, inhibiting effective secondary prevention of myocardial infarction. We aimed to determine the prevalence and incidence of Q-wave UMI in asymptomatic individuals aged 35 to 74years, and to ascertain the positive predictive value (PPV) of asymptomatic Q-wave to diagnose UMI.

METHODS: Two population-based cross-sectional studies were conducted, in 2000 (with 10-year follow-up) and in 2005. A baseline electrocardiogram was obtained for each participant. Imaging techniques (echocardiography, cardiac magnetic resonance imaging, and myocardial perfusion single-photon emission computerized tomography) were used to confirm UMI in patients with asymptomatic Q-wave.

RESULTS: The prevalence of confirmed Q-wave UMI in the 5580 participants was 0.18% (95% confidence interval [CI]: 0.10-0.33) and the incidence rate was 27.1 Q-wave UMI per 100,000person-years. The proportion of confirmed Q-wave UMI with respect to all prevalent MI was 8.1% (95% CI: 4.4-14.2). The PPV of asymptomatic Q-wave to diagnose Q-wave UMI was 29.2% (95% CI: 18.2-43.2%) overall, but much higher (75%, 95% CI: 40.9-92.9%) in participants with 10-year CHD risk ≥10%, compared to lower-risk participants.

CONCLUSION: Opportunistic identification of asymptomatic Q-waves by routine electrocardiogram overestimates actual Q-wave UMI, which represents 8% to 13% of all myocardial infarction in the population aged 35 to 74years. This overestimation is particularly high in the population at low cardiovascular risk. In epidemiological studies and in clinical practice, diagnosis of a pathologic Q-wave in asymptomatic patients requires detailed analysis of imaging tests to confirm or rule out myocardial necrosis.