ABSTRACT
On the other hand, it is well established from the results of several multicenter international randomized trials that, using this type of criteria for candidate selection, there is a constant proportion (approximately 30%) of non-responders among patients treated with CRT.12,13 It has been suggested that a percentage of non-responders may be attributable to the fact that patients may show a wide QRS but do not have mechanical dyssynchrony in ventricular contraction, and therefore CRT is useless simply because there is no myocardium to resynchronize. Therefore, several authors have underlined the importance of demonstrating mechanical dyssynchrony by imaging techniques before implanting a CRT device, in order to improve the clinical outcomes after CRT. Imaging techniques, not only can demonstrate mechanical dyssynchrony, but can also delineate the extent of the scar tissue not amenable to resynchronization.14
