Diagnostic performance of the fragmented QRS complex on electrocardiogram for detecting myocardial scars assessed by 3.0 Tesla cardiac magnetic resonance imaging
Authors: Viriyanukulvong Kasin , Theerasuwipakorn Nonthikorn , Wongcharoen Wanwarang , Kosum Paisit , Chokesuwattanaskul Ronpichai 
Published: July 2024

Background
Fragmented QRS complex (f-QRS) on a 12-lead electrocardiogram (EKG) with a 0.15–100 or 150 Hz low-pass filter is known to be related to ischemic myocardial scars. Cardiac magnetic resonance (CMR) imaging enhances tissue characterization capability resulting in a better myocardial scar assessment over other noninvasive imaging modalities. However, the diagnostic values of f-QRS on non-ischemic scars and f-QRS from EKG with a 015–40 Hz low-pass filter (routine filter in clinical practice) are unknown. This study aims to evaluate the diagnostic performance of f-QRS (from EKG with 0.15-40 and 0.15–100 Hz low-pass filters) for detecting any myocardial scars (both ischemic and non-ischemic) assessed by 3.0 Tesla CMR.
Methods
This cross-sectional study included patients who underwent a 3.0 Tesla CMR scan from May 2020 to May 2023. A 12-lead EKG with 0.15-40 and 0.15–100 Hz low-pass filters, performed on the same day of the CMR scan, was assessed for the presence of f-QRS. The ECG leads were divided into 3 categories (e.g., anterior leads V1-V4; lateral leads I, aVL, V5-V6; and inferior leads II, III, aVF). The f-QRS was defined as the presence of R’ wave or notching in the nadir of the S wave in 2 contiguous leads. The primary outcome was the diagnostic performance of f-QRS from EKG in myocardial scar detection in the corresponding left ventricle (LV) segments. The secondary outcomes were to compare the diagnostic performance of f-QRS in detecting ischemic scars and non-ischemic scars, the diagnostic performance between f-QRS diagnosed from 0.15-40 and 0.15–100 Hz low-pass filters, and the diagnostic performance of f-QRS presented in 2 consecutive leads and f-QRS presented in solitary lead.
Results
The study involved 1,692 participants with a median age of 67 (IQR: 59–85) years old and 52.5% males. Myocardial scars were found in 826 (49%) participants. Male, history of CAD, and myocardial scars were significantly more frequent in the participants with f-QRS (59.4% vs 46.0%, 26.4% vs 20.6%, and 48.9% vs 37.3%, respectively), while median LVEF was lower (61%, IQR 47, 66 vs 62%, IQR 55, 68; p < 0.001). The sensitivity, specificity, positive predictive value, negative predictive value, and AUC of f-QRS from EKG with 0.15–100 Hz low-pass filter for detecting myocardial scars were 25.6%, 88.7%, 45.1%, 76.8%, and 0.57 for anterior segments; 22.1%, 91.5%, 36.8%, 84.1%, and 0.57 for lateral segments; and 42.9%, 63.4%, 36.9, 68.9%, and 0.53 for inferior segments. The sensitivity, PPV, and positive likelihood ratio (LR+) of f-QRS were higher for detecting non-ischemic scars while specificity, NPV, negative likelihood ratio (LR-) and AUC were not significantly different. The f-QRS from 0.15–100 Hz showed a higher sensitivity but lower specificity, PPV, and LR + for all LV segments. The f-QRS presented in the solitary lead showed a higher sensitivity with a lower specificity, PPV, and LR+.
Conclusion
This study demonstrates a high specificity and negative predictive value of f-QRS from a 12-lead EKG with 0.15-40 and 0.15–100 Hz low-pass filters in diagnosing myocardial scars when correlated to the corresponding LV segments.