Pereira H, et al. - In view of the observation that cardiac resynchronization therapy (CRT) is generally delivered via quadripolar leads, and assessment of the effect of different vector programs from quadripolar leads on ventricular activation can be done using non-invasive electrocardiographic mapping (ECM), researchers constructed activation maps in 19 patients with quadripolar LV leads. Observations revealed that in both ischaemic and non-ischaemic subjects, changes in the configuration of an LV quadripolar lead significantly affect ventricular activation timings. Thereby suggesting the necessity for individually tailoring programming of the optimal pacing vector.