Echocardiographic Assessment of Cardiac Dyssynchrony. Where do We Stand?

During the last two decades there has been an increasing interest in cardiac resynchronization therapy (CRT) in patients with heart failure. Major randomized clinical trials which tested the effectiveness of CRT included patients based on electrocardiographic (ECG) criteria amongst other features. However, there is an assumption that mechanical synchrony, as may be assessed by echocardiography, is the underlying mechanism that improves left ventricular function and finally the clinical outcome. Large multi-centre trials have failed to prove the usefulness of echocardiography in both selection of patients for CRT and identification of non-responders. On the contrary smaller trials from centres where there is high expertise in echo techniques have demonstrated that mechanical dyssynchrony can be assessed by echocardiography and can actually predict the response to CRT in a better way than traditional ECG criteria. In this manuscript, we have analysed current evidence from published data and attempted to provide insight to the field of cardiac dyssynchrony as assessed with echocardiography.