Using electrocardiography studies report approximately 20% of myocardial infractions are silent.
Cardiac magnetic resonance can identify myocardial scars, and is significantly better in detection of previous myocardial infarction than clinical assessment, serum biomarkers, and EKG.
The prevalence of myocardial scars in a US based cohort was 7.9%, of which 78% were unrecognized by electrocardiography or clinical evaluation open (Turkbey EB et al).
In the above study only 1.7% of patients had clinically recognized previous myocardial infarctions.
Prior myocardial scar has been noted pathologically in more than 70% of patients with sudden cardiac death but without prior known coronary artery disease.
Studies have shown myocardial scar is associated with an absolute 8% increase in risk in mortality compared with no scar (Schiebart EB et al).