The QRS narrowing index predicts reverse left ventricular remodeling following cardiac resynchronization therapy.

BACKGROUND

The relationship between QRS narrowing and response to cardiac resynchronization therapy (CRT) has been controversial.

OBJECTIVE

We sought to analyze the relationship between QRS narrowing and reverse remodeling in patients undergoing CRT, taking into account potential confounders including pre-CRT QRS duration and underlying QRS morphology.

METHODS

We reviewed pre- and postimplant electrocardiograms and echocardiograms in a cohort of 233 patients undergoing the new implantation of a CRT device between December 2001 and September 2006. For inclusion in the final cohort, patients had New York Heart Association classes II-IV heart failure, left ventricular ejection fraction (LVEF) ≤ 40%, and QRS duration ≥120 ms. Response to CRT was defined as a reduction in left ventricular end-systolic volume (LVESV) of ≥10%. A multivariate model was constructed to determine the relationship between QRS change and response to CRT.

RESULTS

Patients with QRS narrowing had significantly greater reductions in left ventricular end-diastolic volume (LVEDV) (mL) (-26.5 ± 52.5 vs -4.8 ± 44.0, P = 0.002) and LVESV (mL) (-34.0 ± 55.5 vs -9.9 ± 45.8, P = 0.002) and improvement in LVEF (%) (8.9 ± 12.8 vs 4.5 ± 9.0, P = 0.007) than patients without narrowing. In univariate analysis, female gender (P = 0.0002), percent QRS narrowing from baseline (P = 0.008), lack of nitrate (P≤0.0001) and antiarrhythmic medication use (P = 0.01), lack of a nonspecific intraventricular conduction delay (=0.02), nonischemic cardiomyopathy (P = 0.003), and lower pre-CRT LVEDV (P = 0.006) and LVESV [P = 0.01]) were associated with responders. In a multivariate model, QRS narrowing, indexed to the baseline QRS duration, remained strongly associated with response (odds ratio 0.08 [0.01-0.56], P = 0.01).

CONCLUSIONS

After adjusting for potential confounders, QRS narrowing, indexed to baseline QRS duration, is associated with enhanced reverse ventricular remodeling following CRT.