Relationship between fragmented QRS and response to cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure (HF) with a wide QRS. Fragmented QRS (fQRS) on a 12-lead electrocardiography (ECG) has been shown to predict cardiac events in several patient populations. We aimed to investigate the relationship between fragmented wide QRS (f-wQRS) and left ventricular dyssynchrony and response to CRT.

Fifty-three patients with HF undergoing CRT were studied. The presence of fQRS was assessed using standardized criteria. Dyssynchrony was defined as interventricular mechanical delay (IVMD) ≥40 ms and tissue Doppler velocity opposing-wall delay ≥65 ms. Echocardiographic response to CRT was defined by a ≥15 % reduction in left ventricular end-systolic volume at 6 months follow-up.

Fragmented wide QRS was present in 17 (32 %) patients. Interventricular and intraventricular dyssynchrony were highly prevalent in both patient groups with f-wQRS and nonf-wQRS (64.7 % vs 75 %, p = 0.44; 70.6 % vs 72.2 %, p = 0.25). Ischemic HF was significantly higher in patients with f-wQRS than patients with nonf-wQRS (64 % vs 33 %, p = 0.03). Reverse remodeling was developed in 32 (89 %) and 6 (35 %) of patients with nonf-wQRS and f-wQRS, respectively (p = 0.001). In multivariate analysis, significant associates of response to CRT were evaluated adjusting for etiology of cardiomyopathy, QRS width, IVMD, intraventricular delay, and f-wQRS. Lack of f-wQRS was the only predictor of response to CRT (OR 1.556, 95 % CI, 0.016-0.806, p = 0.028).

Presence of dyssynchrony is necessary but not sufficient to select appropriate candidates for CRT. Presence of f-wQRS on baseline ECG may play a role in identifying patients who may not respond to CRT.