Cardiac-Resynchronization Therapy with or without an Implantable Defibrillator in Advanced Chronic Heart Failure

Some patients with chronic heart failure have intraventricular conduction delays, which cause asynchronous contraction of the left ventricle. This large clinical trial confirmed that biventricular pacing to restore synchronous contraction has significant benefits in such patients. The addition of an implantable defibrillator further reduces mortality. Resynchronization therapy may have clinical benefit, especially when combined with an implantable defibrillator. Intraventricular conduction delays are associated with dyssynchronous left ventricular contraction caused by regional delays in the electrical activation of the chamber. 1 , 2 This phenomenon, which occurs in 15 to 30 percent 3 – 5 of patients with heart failure due to dilated cardiomyopathy, reduces systolic function and increases systolic volume. 6 – 8 In patients with primary or secondary dilated cardiomyopathies characterized by intraventricular conduction delays, biventricular stimulation synchronizes the activation of the intraventricular septum and left ventricular free wall and thus improves left ventricular systolic function. 6 – 8 In short-term studies, cardiac-resynchronization therapy in the form of biventricular stimulation improved symptoms, 9 – 12 improved the . . .