Background Recent clinical trials have challenged the clinical applicability of mechanical dyssynchrony in predicting cardiac resynchronisation therapy response.

Objective To evaluate whether mechanical dyssynchrony has an additional benefit over QRS duration in predicting cardiac events in patients with systolic heart failure.

Methods A total 167 patients admitted to hospital with heart failure (age 65±12, ejection fraction <35%) were followed up prospectively. Using tissue Doppler imaging (TDI), the time to peak systolic velocity during the ejection phase was measured in the basal septal and lateral segments. A temporal difference between the septal to lateral wall (Ts−l) of ≥65 ms was defined as a mechanical dyssynchrony.

Results After 33 months of follow-up, 70 patients (41.9%) had cardiac events, including 42 (25.1%) with cardiac death. The event-free survival time decreased as Ts−l or QRS duration increased. Patients with QRS ≥120 ms had increased risks of cardiac events by multivariate Cox proportional hazard analysis (HR=1.88, 95% CI 1.07 to 3.29, p = 0.028). The presence of mechanical dyssynchrony also predicted an increased risk of cardiac events (HR=2.37, 95% CI 1.39 to 4.04, p = 0.002). Those with both electrical and mechanical dyssynchrony had a HR of 3.98 (95% CI 2.02 to 7.86, p <0.001) when compared with those with normal QRS duration and absence of mechanical dyssynchrony. The addition of mechanical dyssynchrony significantly improved the prognostic power of a model containing echocardiographic parameters and QRS duration.

Conclusions TDI-derived mechanical dyssynchrony is an important prognosticator and independently associated with QRS duration in predicting adverse events in patients with systolic heart failure.