Septal notch plus loss of the septal q wave: A potential early ECG sign suggestive of interstitial septal fibrosis in heart disease

Abstract

Background

Early detection of interstitial septal fibrosis remains challenging. We describe a novel ECG pattern that may represent an early marker of fibrotic conduction changes.

Case findings

We evaluated a case demonstrating a triphasic QRS sequence evolving from narrow QRS (88 ms) to complete LBBB-like pattern (160 ms) within three beats. Notable features included: (i) a subtle notch within the initial 20 ms of QRS in leads II, V5 and V6; (ii) disappearance of physiological septal q waves in V5–V6; (iii) multiple notches in leads II, V4-V6; and (iv) late-QRS notching in leads III, aVL, aVF. These findings differed significantly from true LBBB criteria.

Interpretation

This ECG pattern may represent functional conduction alternans within fibrotic myocardium rather than anatomical His-Purkinje block. The presence of preserved rapid early forces, absence of mandatory mid-QRS notching in lateral leads, and reduced lateral voltage suggests myocardial conduction slowing rather than true complete LBBB.

Limitations

This is a single-case observation without confirmatory cardiac MRI or histopathology. Computer modeling referenced was not performed by our group. The proposed mechanism remains hypothetical and requires validation in prospective cohorts.