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[Selection of patients for resynchronization therapy. "The role of echocardiography"].

Heart failure is one of the most prevalent diseases in industrialized countries in especial persons more 65 years. In the last 2 decades new therapies have been investigated and first time it had improved quality of life and survival. However, up to 30% of the patients with advanced heart failure present disturbances in inter and intraventricular conduction, and this produces asynchrony or dyssynchrony of ventricular contractility, leading to further deterioration in heart function. Cardiac resynchronization therapy can improve the synchrony of ventricular contractility. Numerous studies have demonstrated the benefits of biventricular stimulation therapy for improving hemodynamic parameters, quality of life, 6- minute walking test performance and functional class in patients with heart failure, ventricular systolic dysfunction and disturbances in intraventricular conduction. Around 30% of patient do not respond to resynchronization therapy. There is a poor correlation between QRS interval and mechanical asynchrony. Echocardiography is better at assessing mechanical asynchrony than QRS interval measurement. The aim of this article was to review the different techniques echocardiography's to guide in the selection patients who benefice of resynchronization therapy.