QRS fragmentation versus QRS prolongation in predicting right ventricular enlargement and dysfunction in children and adults with repaired Tetralogy of Fallot

Abstract

Patients with repaired Tetralogy of Fallot (rTOF) have risks of late life-threatening sequelae, including right ventricular (RV) dilation and failure, arrhythmias, and sudden death. QRS prolongation is a well-known ECG predictor of these outcomes but has poor sensitivity for mortality. Growing evidence demonstrates QRS fragmentation (fQRS) as a better prognostic marker for mortality in adults with rTOF, though the two markers have not been directly compared as correlates for CMR abnormalities. Additionally, fQRS has never been studied in pediatric TOF. This single institution retrospectively reviewed 138 CMRs in rTOF patients (median age 21.7 years) who had a corresponding 12-lead ECG within 1 year. fQRS was defined as ≥3 R-waves/notches in the R/S complex (>2 in right bundle branch block) in ≥2 contiguous leads. QRS prolongation was defined as QRS ≥160 ms. Nearly half (46%) the sample had fQRS (42.1% of pediatric subgroup), and 26% had QRS prolongation. Both markers were significantly associated with reduced RV ejection fraction (EF%) (p < 0.01) and larger RV end-diastolic volumes (p < 0.01). QRS prolongation alone predicted lower LV EF% (p = 0.02). Regression analyses showed both QRS prolongation (p < 0.01) and fQRS (p < 0.01) independently associated with reduced RV EF%; QRS prolongation alone predicted RV dilation (p < 0.01). We concluded that both QRS prolongation and fQRS are equivalent as significant markers of RV dysfunction in rTOF patients. QRS prolongation may be a better surrogate for RV dilation specifically. fQRS was frequently seen in children with rTOF and was significantly associated with similar late structural sequelae.

Keywords: QRS fragmentation; Tetralogy of Fallot.

Fig. 1

Example of QRS fragmentation. Patient with repaired Tetralogy of Fallot and right bundle branch block with fragmented QRS complexes in leads V2, V3, V4, and V5. Fragmentation is defined as characteristic 3 notches in the R/S complex in the presence of a right bundle branch block, a common finding in rTOF patients.

Fig. 2

Distribution of fQRS complexes in entire cohort by ECG lead segments. Distribution of fQRS complexes by individual ECG lead segments. Leads V1–V5 represent anteroseptal region; leads V6, I, aVL represent lateral segments; and leads II, III, aVF represent inferior region.

Fig. 3

Cardiac MRI trends with fQRS and prolonged QRS duration in patients with repaired Tetralogy of Fallot. Multivariable analyses of ECG markers with ventricular abnormalities on CMR. Left graph shows fQRS and QRS prolongation, “QRSp,” to be independently associated with increased RVEDVi. (p = 0.01 and p < 0.01, respectively). Middle graph shows fQRS and QRSp as each independently associated with reduced RV EF% (p < 0.01 for each marker). Right graph shows that fQRS was not significantly associated with differences in LV EF%. The presence of QRSp was independently associated with reduced LV EF% (p = 0.02).