Native QRS narrowing reflects electrical reversal and associates with anatomical reversal in cardiac resynchronization therapy.

PURPOSE: Abbreviation of paced QRS duration has been taken as electrical resynchronization imposed by cardiac resynchronization therapy (CRT). However, little is known about alteration in native QRS duration and its correlation with therapeutic response as well as anatomical remodeling post-CRT.
METHODS: Data of 74 consecutive patients with complete ECG records were reviewed. Response was defined as absolute improvement in LVEF by ≥10% from baseline. Changes in native QRS duration (native ΔQRS) were analyzed to CRT response and to changes in echocardiography.
RESULTS: Over median follow-up of 13 months, 47 patients had response to CRT and 30 subjects had abbreviation in native QRS duration. Native ΔQRS correlated positively with QRS duration pre- and post-CRT as well as with changes in echocardiography. Reversal of electrical remodeling as assessed by native QRS narrowing accompanied with greater improvements in LVEF (20% ± 11% vs 10% ± 10%, p = 0.000) and LVEDD (14 ± 11 mm vs. 4 ± 10 mm, p = 0.000). Multivariate analysis indicated that native ΔQRS was the lone independent factor of ECG in association to response to CRT (OR1.049, 95%CI 1.015-1.085, p = 0.004): 83.3% of patients with native QRS reduction were responders. Among the non-responders, 18.5% had native QRS narrowing at follow-ups.
CONCLUSIONS: Native QRS narrowing associated with beneficial response and greater improvements in echocardiography. Abbreviation in native QRS duration could reflect electrical reversal imposed by CRT.