Optimization of cardiac resynchronization therapy: importance of programmed parameters.

One of the basic tenets of cardiac resynchronization therapy (CRT) is that optimization of programmed parameters is important to maximize the therapeutic response. Both atrioventricular (AV) and interventricular (VV) timing intervals have been suggested as potential methods to improve response rates. A variety of techniques have been described to determine the optimal AV and VV delays. Many of these methods have demonstrated acute hemodynamic benefits; however, multicenter data proving long-term clinical benefit have been lacking. Echocardiography-guided methods have been most commonly employed, but no technique has been shown to be superior. In fact, many of these techniques have poor reproducibility and are time-consuming. Device-based algorithms allow for a rapid, simplified approach to CRT optimization; however, their clinical value has also been called into question. This review will describe the different techniques for CRT optimization and evaluate their potential value and limitations.