Cardiac resynchronization therapy : advances in optimal patient selection

Despite the impressive results of cardiac resynchronization theraphy (CRT) in recent large randomized trials a consistent number of patients fails to improve following CRT implantation when the established CRT selection criteria (NYHA class III-IV heart failure, LV ejection fraction __35 % and QRS duration > 120 ms) were applied. For example, close analysis of the data from the MIRACLE trial revealed that 32% of patients did not improve or even worsened in NYHA class after 6 months of CRT. The presence of clinical non-responders to CRT has now been confirmed in several other studies and is usually around 30%. In addition, if response to CRT is defined using more objective parameters such absence of LV reverse remodeling or lack of improvement in LV ejection fraction on echocardiography at mid-term follow-up the number of non-responders is usually between 40-50%. In view of the unnecessary procedure risks and health care expenses in patients without response to CRT the percentage of non-responders among patients selected according to the current selection criteria is unacceptably high and should be reduced. Aim of the thesis: The relatively high number of patients without benefit from CRT (referred to as non-responders) indicates the need for refinement of the current selection criteria in order to 1] better identify those patients with the highest likelihood of response to CRT and 2] avoid device implantations in patients that are unlikely to respond to CRT. The aim of the current thesis was to improve and refine the current CRT selection criteria through the evaluation of the mechanismus underlying (non-) response to CRT