[Cardiac resynchronization therapy].
Despite recent advances in pharmacologic treatment for heart failure, the prognosis of patients with chronic heart failure remains poor. One third of patients with chronic heart failure have intraventricular conduction delay. The ventricular mechanical dyssynchrony based on intraventricular conduction delay worsen ventricular systolic dysfunction. Cardiac resynchronization therapy(CRT) through biventricular pacing significantly improves symptoms, exercise tolerance, hemodynamics, hospitalization for heart failure and mortality. However, it is estimated that 30 % of patients do not respond to CRT. A direct assessment of mechanical dyssynchrony with echocardiography seems more important than QRS duration in selecting appropriate patients for CRT.