Left ventricular endocardial pacing and multisite pacing to improve CRT response.

Cardiac resynchronization therapy (CRT) is an established treatment for patients with moderate-to-severe heart failure and a wide QRS complex. However, the amount of reverse remodeling and clinical improvement is highly variable and poorly predictable. The left ventricular pacing site is of critical importance for the CRT response but is often imposed by the coronary sinus anatomical constraints and may result in suboptimal resynchronization. Alternative pacing sites, such as endocardial LV pacing or multisite pacing, have been proposed to improve CRT response rates and may be considered in nonresponders to standard resynchronization. However, adequately powered randomized studies are required to determine whether these pacing strategies result in improved outcome.