A lot of studies using different cardiac imaging (echo, MRI, SPECT) tried to find a parameter which better predict CRT response; these studies analysed mostly presence of mechanical dyssynchrony and the distribution or burden of nonviable myocardium.

Echocardiography is very useful and widespread available tool to assess mechanical dysynchrony and numerous echocardiographic parameters and techniques have been used to assess for dyssynchrony (M-mode, PW Doppler imaging, TDI, speckle tracking, and 3D echocardiography). According to the small studies, different echocardiographic parameters of dyssynchorny were related to CRT response. Unfortunalely, according to a large, nonrandomized, multicenter study (PROSPECT) none of the 12 baseline echocardiographic dyssynchrony parameters proved to be sensitive or specific enough to be useful for predicting CRT response. Different MRI techniques for assessment of intramyocardial deformation (especially myocardial tagging) have also been used in CRT patients. There is lack of large studies to define the rule of MRI parameters of dysynchrony in CRT patients. However, there are more data regarding the burden and distribution of scar assessed by MRI in CRT patients. Patients with the large area of myocardial scar and presence of transmurale scar in the pacing site were associated with nonresponse to CRT. Similar results were also found in nuclear imaging studies (single-photon emission computed tomography (SPECT) myocardial perfusion imaging), where amount and localisation of nonviable myocardium were related to nonresponse (my article http://www.ncbi.nlm.nih.gov/pubmed/24136364)

According to my opinion, there is no single imaging parameter that can simply define responders in CRT candidate. By using multimodality imaging (echo, nuclear imaging or MRI) and integration information of dyssynchrony, area of latest mechanical activation, scar or viability for individual patient, might improve response in CRT patients.

I would definitely agree with dr. Cvijić regarding imaging modalities that help identify possible CRT responders. However, i would stress that CRT is an electrical therapy and should be taken as such. I my view imaging in CRT should be used to asses the baseline cardiac function + scar burden for addition info about the possibility of cardiac recovery after the electrical dissinhrony after CRT is maybe resolved (QRS narrowing).

Everything is said. There is no imaging technique available up to now, which can predict the response to CRT-therapy. (3 D-) echocardiography can show us the degree of dyssynchrony in connection with reduced ventricular function quite well and MRI or SPECT may add some valuable information about scar burden, but more information cannot be obtained byeither method. Much more attention should be paid to the preoperative electrophysiological data, to the implantation site of the LV-electrode and to the subsequent changes in QRS-complex pre and under pacing, as already pointed out by Marta and David.

i agree with the previous. ECHO technological advances such as speckle tracking strain and real-time three dimensional imaging are under study. There has been evidence that the use of speckle-tracking echocardiography to the target LV lead placement may improve clinical outcome (TARGET Trial).

Today, there is no imaging technique which can predict CRT response before implantation. The only thing that could predict the 6 months good response to CRT (LVESV < 10% t 6 months) is the precocious qrs reduction after crt implantation: infact a precocious electrical remodeling shold be determine an anatomical response leading to a 6 months reverse remodeling. You can find on PUBMED some evidences about QRS indexing reductiong,

I agree with Marta and David. Image diagnosis of large scar areas and dyssynchrony are not preditive of CRT results.

In my opinion, multimodal imaging will play a key rule in the prediction of response to CRT. Novel approaches such as three-dimensional reconstruction of CS lead tip movements throughout cardiac cycle could be useful for evaluating the resynchronization process. This study shows the preliminary results of an ongoing project. 

http://www.ncbi.nlm.nih.gov/pubmed/23851066

Since Echocardiography do not contributes in decisions making nor does it assess the outcome of the CRT. It is our practice only we look at the routine base line echocardiographic parameters only.