In Search of a Holy Grail

Abstract

“It came out of nowhere and captured the cardiology community by storm.” The cliche seems very appropriate when describing the impact of cardiac resynchronization therapy (CRT) on the treatment of heart failure. CRT improves survival rate in symptomatic patients 1 and is the only nonsurgical technique that provides substantial and stable reverse remodeling in both symptomatic and asymptomatic patients.2,3 The most surprising fact is that this is accomplished through mechanisms that are still unclear and that are not fully elucidated in experimental models. CRT is the only heart failure therapy with a potential to improve survival rate that is not based on neurohormonal modulation. Finally, it represents a challenge to the imaging community, as it establishes a need to measure something that was previously overlooked—dyssynchrony. Article see p 14 Unfortunately, CRT is not universally successful. One third of CRT patients do not feel better,4 and close to 40% of patients do not experience reverse remodeling, which is important because it predicts survival rate.5 This should not be a surprise—treatment of chronic diseases is rarely homogenously beneficial to all the patients. Nevertheless, in the case of CRT, some extra precautions are necessary. CRT is expensive; placement of electrodes may be difficult; and, even in experienced centers, a significant number of patients may require surgical placement. Finally, it is an expensive, healthcare-intensive therapy with extensive follow-up and occasional complications. Thus, there is an ongoing search for practical methods to predict the outcome of CRT and guide its use. Current guidelines use QRS duration (and symptoms) as the principal determinants for implantation, and as noted, this is fairly successful, with two thirds of such patients demonstrating improvement. The real challenge for clinicians comes in two situations: identifying those patients with narrow QRS who are …