Valoración ecocardiográfica de la asincronía

Cardiac resynchronization therapy has been shown to be effective in selected patients with heart failure. The current selection criteria are: a) New York Heart Association (NYHA) functional class III or IV heart failure despite optimized medical therapy; b) depressed left ventricular ejection fraction (LVEF<35%); c) left ventricular end-diastolic diameter 55 mm; and d) a wide QRS complex (>130 ms) with evidence of left bundle branch block (LBBB). However, these criteria are under revision. Around 30% of patients selected using these criteria do not respond to resynchronization therapy. There is a poor correlation between QRS interval and mechanical asynchrony, with over 51% of patients with a QRS interval less than 120 ms having mechanical asynchrony. Echocardiography is better at assessing mechanical asynchrony than QRS interval measurement. Moreover, recent data suggest that echocardiography provides the best predictors of improvement after resynchronization therapy. Several methods have been shown to be useful in predicting a good response. However, there are discrepancies between the results of the different methods and no consensus on the best approach has yet been reached. Nevertheless, echocardiography should be included in any evaluation of candidates for resynchronization therapy. The aim of this article was to review the benefits and limitations of existing criteria.