Seeing is believing: acute haemodynamic response to predict long-term outcome in cardiac resynchronization therapy

‘An acute hemodynamic study … was performed prior to the implant, which demonstrated a significant increase in cardiac output and decrease of pulmonary capillary wedge pressure’ (1) Many heart failure specialists still believe that the pathophysiology of cardiac resynchronization therapy (CRT) is incompletely understood; however, it must be emphasized that the main effects of biventricular pacing have already been described more than a decade ago.1 In 1994, Cazeau et al .1 reported how biventricular pacing improves clinical signs and symptoms of heart failure, acutely increases cardiac output and decreases pulmonary capillary wedge pressure and that those effects were likely mediated by better synchronization of left ventricular (LV) mechanical contraction. However, despite the obvious clinical success of this novel therapeutic approach, the authors were very modest with speculations on the impact on mortality: ‘We doubt that this technique will have an impact on long-term survival, but it could be of major importance to improve the patients well-being and control heart failure.’ (1) Fortunately, this was the only false estimation at that time. The doubts with regard to the potential survival benefit were later refuted by the results of well controlled, randomized clinical trials which clearly demonstrated a reduced overall mortality in the CRT treatment arm2 and which paved the way for a class I indication in symptomatic heart failure patients with a prolonged QRS complex of 120 ms or above. However, despite the undisputed success of CRT for this selected population, many questions remain. The non-responder rate of more than 30–40% is relatively high for such a costly and invasive therapy and has pushed investigators to search for new strategies to better identify CRT responders and to improve optimization of the device settings. However, there are many reasons that might explain CRT failure. First, heart failure is a … *Corresponding author. Tel: +49 9131 85 35301; fax: +49 9131 85 35303. E-mail address : olebreithardt{at}gmx.de