Cardiac resynchronization therapy: haemodynamic background and perspectives

Cardiac resynchronization therapy (CRT) has become an accepted routine therapy for a subgroup of heart failure patients. Haemodynamic evaluations have yielded data that are essential to our current understanding of the mechanisms of CRT and nearly every step of CRT innovation has been introduced following studies employing relatively complex, invasive haemodynamic measurement techniques, such as conductance catheters for constructing pressure–volume loops and sensor tipped pressure wires in the left ventricle. These studies have been valuable in demonstrating the importance of selecting optimal pacing site and to understand the interactions between right and left ventricles, including the optimal timing for stimulation. The invasive measurements were the only investigations which showed that CRT decreased oxygen consumption and improved work efficacy without additional oxygen demand as seen with catecholamines. The acute haemodynamic effects also appear to be chronically maintained. Even if the invasive haemodynamic evaluations are time-consuming and not always applicable in routine clinical practice, their use should be considered in patients with new or borderline CRT indications to avoid deleterious effects by suboptimal lead placement or programming.