Cardiac resynchronisation therapy: current benefits and pitfalls.

Cardiac resynchronisation therapy (CRT) has been shown to reduce all-cause mortality, heart failure events, and symptoms while improving exercise capacity and quality of life. Nevertheless, despite a large number of multicentre randomised trials and clear evidence confirming the above, there is still a higher number of patients who fail to develop reverse remodelling. In order to select the optimal patient population, the current European Society of Cardiology guidelines recommend a simultaneous evaluation of QRS morphology and width. However, based on recent data, QRS width itself is a less accurate parameter in the prediction of the outcome, as compared to QRS morphology. Furthermore, the baseline left ventricular (LV) ejection fraction (LVEF), which is also an known criterion for selecting CRT candidates (partly applied due to cost-benefit reasons), can be misleading. Data showed that patients with LVEF > 35% might also benefit from this type of treatment. Thus, LVEF should be evaluated less rigorously when screening patients for resynchronisation therapy. While the subsequent beneficial response to CRT is multifactorial, procedure-related parameters, such as LV lead position, are also crucial. The first data released recently confirmed the previous empiric clinical experience indicating that the LV lead should be implanted into the lateral or posterior coronary sinus side branch. This location was associated with a better long-term clinical outcome in terms of death and heart failure events. Some issues related to CRT are awaiting further clarification, such as the choice of the type of the implanted device (pacemaker or defibrillator) or the decision about CRT device upgrade. This review discusses the current evidence regarding the above, focusing on the questions that should be handled with caution or require clarification.