Is CRT response rate all about patient selection?

Under ideal conditions cardiac resynchronisation therapy (CRT) response is a function of the patient's baseline electrical substrate and the improvement derived from manipulating the electrical activation of the heart. Patient response to therapy is thus dependent on the degree to which baseline electrical asynchrony explains their degraded cardiac function and how well CRT manipulates their electrical activation to recover cardiac function. These factors have led to four broad directions for improving CRT response rate: patient selection, pacing technology, device settings and lead position. It is likely that a combination of all four will be required to maximise response in a specific patient. Response to cardiac resynchronization therapy is determined by intrinsic electrical substrate rather than by its modificationInternational Journal of CardiologyVol. 270PreviewElectrocardiographic mapping (ECM) expresses electrical substrate through magnitude and direction of the activation delay vector (ADV). We investigated to what extent the response to cardiac resynchronization therapy (CRT) is determined by baseline ADV and by ADV modification through CRT and optimization of left ventricular (LV) pacing site.