Even with the remarkable results of cardiac resynchronisation therapy (CRT) in the large randomised trials, a steady percentage of patients (30 to 50%) failed to improve after CRT when the established selection criteria (New York Heart Association [NYHA] class III or IV, left ventricular ejection fraction [LVEF] <35% and QRS duration >120 ms) are applied. This high number of non-responders requires readjustment of the current selection criteria. In addition, the exact mechanism and effects of CRT on echocardiographic parameters such as mitral regurgitation and dyssynchrony, as well as long-term outcome and incidence of ventricular arrhythmias are currently unknown. The aim of the present thesis was to further explore these issues using varying noninvasive imaging techniques and device-based diagnostics.
