Objective: Recent clinical trials have challenged the clinical applicability of mechanical dyssynchrony in predicting cardiac resynchronization therapy response. We sought to evaluate that mechanical dyssynchrony had additional prognostic power over QRS duration in heart failure.
Methods: A total 167 patients with hospitalized heart failure (age 65 ±12, ejection fraction < 35%) were followed 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 msec or more was defined as a mechanical dyssynchrony.
Results: After 33 months of follow up, 70 patients (41.9%) had cardiac events including 42 (25.1%) cardiac death. The event free survival time decreased as Ts-l or QRS duration increased. Patients with QRS ≥120 msec had increased risks of cardiac events by multivariate Cox proportional hazard analysis (HR 1.85, 95% CI 1.05 - 3.24, p = 0.032). The presence of mechanical dyssynchrony also predicted an increased risk of cardiac events (HR 2.35, 95% CI 1.37 - 4.01, p = 0.002). Those with both electrical and mechanical dyssynchrony had a HR of 3.98 (95% CI 2.02 - 7.86, p < 0.001) when compared to 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.
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