Background: Fragmented QRS complex (f-QRS) on a 12-lead electrocardiogram (EKG) with a 0.15-100 Hz low-pass filter correlates with ischemic myocardial scars. While cardiac magnetic resonance (CMR) imaging enhances scar assessment, f-QRS diagnostic values for non-ischemic scars and routine 0.15-40 Hz filter EKGs are unknown. This study evaluates f-QRS (from EKGs with 0.15-40 and 0.15-100 Hz filters) in detecting myocardial scars (ischemic and non-ischemic) using 3.0 Tesla CMR. Methods: This cross-sectional study included patients undergoing 3.0 Tesla CMR from May 2020 to May 2023. Same-day 12-lead EKGs with 0.15-40 and 0.15-100 Hz filters were analyzed for f-QRS presence. Leads were categorized (anterior: V1-V4; lateral: I, aVL, V5-V6; inferior: II, III, aVF). f-QRS was defined as R? wave or notching in S wave nadir in 2 contiguous leads. Primary outcome: f-QRS diagnostic performance for myocardial scar detection in corresponding left ventricle (LV) segments. Secondary outcomes: Comparison of f-QRS in detecting ischemic/non-ischemic scars, between filter types, and in consecutive/solitary leads. Results: 1,692 participants (median age 67; 52.5% male) were included. Myocardial scars were found in 49%. Participants with f-QRS had a higher prevalence of male sex, CAD history, and scars. Median LVEF was lower in the f-QRS group. Sensitivity, specificity, PPV, NPV, and AUC of f-QRS (0.15-100 Hz filter) for myocardial scar detection varied across LV segments. Higher sensitivity, PPV, and LR+ were observed for non-ischemic scars with f-QRS. f-QRS from 0.15-100 Hz showed higher sensitivity but lower specificity, PPV, and LR+ across LV segments. Solitary lead f-QRS exhibited higher sensitivity but lower specificity, PPV, and LR+. Conclusion: 12-lead EKGs with 0.15-40 and 0.15-100 Hz low-pass filters show high specificity and negative predictive value for diagnosing myocardial scars corresponding to LV segments.

The authors have declared no competing interest.

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The study protocol was reviewed and approved by the Institutional Research Committee, Faculty of Medicine, Chulalongkorn University (IRB No. 0660/66).

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