ABSTRACT
As detailed in other chapters of this textbook, two unique and distinct devices have been evaluated for the treatment of patients with congestive heart failure: implantable cardioverter-defibrillators (ICD) and cardiac resynchronization devices (CRT). The development of each of these devices was based on a unique hypothesis. In the case of the ICD, investigators hypothesized that because a large number of heart failure patients died suddenly,1 presumably secondary to a lethal tachyor bradyarrhythmia, the ability of an implanted device to sense and defibrillate a tachyarrhythmia or to sense and pace a bradyarrhythmia would be beneficial. Alternatively, the observation that nearly 30% of patients with heart failure had dyssynchronous left ventricular (LV) contraction and that cardiac dyssynchrony was associated with worsened ventricular function, increased myocardial oxygen demand, maladaptive ventricular remodeling, and increased mortality2-5
led investigators to assume that resynchronizing the pattern of ventricular contraction would have salutary benefits. Indeed, these assumptions proved true, as both individual trials6,7 and metaanalysis have demonstrated salutary benefits of both ICD therapy8 and CRT9 in patients with heart failure.
