Perspective:

Up to one out of three patients undergoing CRT implantation do not derive a clinical benefit. The possible explanations are poor candidate selection, suboptimal device programming, and placement of the leads. RV apical pacing may adversely affect cardiac function in patients with and without cardiomyopathy, and there has been a great deal of interest in finding the ‘optimal’ site for RV lead placement, with some studies suggesting that RV outflow tract (high septal) pacing is better. Retrospective analysis of prior studies suggested that the apical position of the left ventricular lead was associated with poor response to CRT. In the present study, atrioventricular delay optimization was performed before discharge using the iterative mitral flow method under echocardiography, which is generally not performed in clinical practice. I was also surprised by the exceedingly high complication rate of 26%. It would be interesting if the authors had reported the activation delays between the electrodes, a variable which has been associated with differential response to CRT. In the end, it remains unclear as to what is the optimal position of the RV electrode.