QRS fragmentation is not associated with poor response to cardiac resynchronization therapy

Background: QRS fragmentation (fQRS) has been shown to be a marker of scar in patients with left ventricular dysfunction. Whether fQRS is associated with progressive left ventricular remodeling and increased mortality in patients receiving cardiac resynchronization therapy (CRT) is unclear. Methods: We reviewed the preimplant and follow-up echocardiograms in 233 patients undergoing the new implantation of a CRT device between December 2001 and November 2006. Patients were included if they had a pre-CRT ECG with appropriate filter settings (filter 0.16-100 or 0.16-150 Hz, 25 mm/s, 10 mm/mV), a left ventricular ejection fraction (LVEF) ≤40%, and New York Heart Association class II-IV symptoms on standard medical therapy. The 12-lead electrocardiogram (ECG) was interpreted by two blinded reviewers for the presence of fQRS. Remodeling end points, including changes in LVEF and left ventricular end-diastolic (LVEDV) and systolic (LVESV) volumes, were compared between patients with and without contiguous fQRS, and an assessment of all-cause mortality was made. Results: Two hundred thirty-two patients met inclusion criteria, of which 50 demonstrated fQRS in contiguous leads. There was no difference in improvement in LVEF (%) (7.9 A;circ± 12.9 vs 6.8 ± 11.0, P = 0.60) or reduction in LVEDV (mL) (-30.1 ± 57.2 vs -15.7 ± 47.6) or LVESV (mL) (-33.7 ± 58.1 vs -22.7 ± 50.6, P = 0.40) between patients with and without contiguous fQRS. At a mean follow-up of 4.4 ± 1.9 years, there were a total of 89 deaths, 22 (44.0%) in patients with contiguous fQRS and 67 (36.8%) without (log rank P = 0.31). Conclusions: QRS fragmentation is not a predictor of progressive ventricular remodeling or mortality in heart failure patients undergoing CRT.