Cardiac resynchronization therapy: caveat medicus! Review Article

The device era in heart failure has been heralded by successes in the realm of pacemakers, implantable defibrillators, and ventricular assist devices. In particular, the concept of cardiac resynchronization therapy, which seeks to optimize ventricular contractility by decreasing areas of focal dyssynchrony, is gaining wide acceptance. Recent trials of cardiac resynchronization therapy have suggested that this treatment modality yields benefits that are reflected in improved functional capacity, reversal of ventricular modeling, and decreased hospitalizations. Cardiac resynchronization device therapy exerts a substantial placebo effect, with evidence of improved functional capacity and quality-of-life parameters in almost half of those in the control group, probably as a result of device implantation. Furthermore, analysis of the different trials suggests heterogeneity of response (differences in magnitude of observed benefit between trials presumably enrolling similar heart-failure populations) and a large non-responder rate (no improvement in functional capacity and well-being). The appropriate approach to resynchronization must include much more than simple characteristics of device implantation. We must detect the presence and precise location of mechanical dyssynchrony and be able to find the technical location and place the pacing leads in the appropriate position. Finally, we must be able to show evidence for sustained improvement in ventricular dyssynchrony. Thus, the current approach to resynchronization represents a “best guess” approach to achieving resynchronization by observation of surrogate responses. Continued investigation to determine optimal approaches for achieving a beneficial clinical response is essential to ensure that cardiac resynchronization therapy is offered to those most likely to benefit.